DOHC or SIBC for Corvette C7

[ShadowDog]

Other companies managed to fit DOHC V6s in cars similar in size, or smaller, than GM's midsized cars, and many were fairly easy to get to the spark plugs.

For some reason I can't attach pictures, but go here and look at the location of the spark plugs.

http://www.attarco.com/images/K8.jpg

Those red wires against the firewall connect to foot long plastic housings that slide deep past the camshaft heads into the block. If the entire engine was an all-new design from the block on up, then this issue may not have been so significant. This wasn't an all-new design, but had carry-over parts similar to the 3.1 L pushrod. GM worked with what they had available without having to go from scratch because, well, they couldn't.

[ShadowDog]

Maybe for those in the cold weather. In AZ, my L67 was retarding the timing so much that it probably only had 210hp when the temp rose above 80 degrees. After adding a cam, intercooler, and smaller pulley, it cracked a piston.

I get the feeling not every other engine in existence was immune to the climate in Arizona.

[Robert Hall]

I get the feeling not every other engine in existence was immune to the climate in Arizona.

Well, it is one of the most vile and disgusting climates in the US...kills quite a few engines every year, no doubt. Killed my cooling system after 2 summers. I hope to get out of the endless dull and blandscape of Chandler and Phoenix before next summer...

[smk4565]

Think about it though...GM never developed the Northstar to anywhere near its full potential.

they can come much closer to developing an LS based mill to its full potential.

And as for not spending $300 million...why should they? They just lost over a billion dollars. Pissing away another 300 million on a low volume car like the Corvette makes NO rational sense whatsoever.

Chris

Because the DOHC V8 could be used for Cadillac (as well as any full size trucks) in addition to the Corvette. Plus the technology derived from that DOHC V8 can trickle down to 4 and 6 cylinders. Hyundai spent a few hundred million on the Tau V8, they didn't do that just to put it in the Genesis and not carry anything over to other models.

Ford has a new DOHC V8 coming for the Mustang, F150 and possibly an Ecoboost V8 with over 500 hp for the Shelby GT500. Everyone else (except Chrysler) is spending on R&D, GM has to keep up. Otherwise this will be like 2000-2005 when GM had the 3800 V6/4-speed auto and the imports had more advanced engines/transmissions and stole a lot of market share.

[CaddyXLR-V]

I get the feeling not every other engine in existence was immune to the climate in Arizona.

Because it was supercharged with no intercooler, the effect was much more pronounced.

Edited November 20, 2009 by CaddyXLR-V

[smk4565]

Another possible scenario is making the Corvette a twin turbo V6. The GT-R matches a Z06 in a straight line and beats iton the Nurburgring, and the GT-R is heavier and has a back seat. If they want to keep the Vette light and meet CAFE/emissions regs, the V6 may become the standard engine. And if they want to grow sales abroad, that could be a good idea as some countries tax displacement. Although personally, I'd want a V8.

[Robert Hall]

Otherwise this will be like 2000-2005 when GM had the 3800 V6/4-speed auto and the imports had more advanced engines/transmissions and stole a lot of market share.

And in 2010, GM still is doing pushrod V6s and 4spd autos in some models..look at the Impala, totally outclassed by the Taurus, selling only on price. Sad situation.

[CaddyXLR-V]

Because the DOHC V8 could be used for Cadillac (as well as any full size trucks) in addition to the Corvette. Plus the technology derived from that DOHC V8 can trickle down to 4 and 6 cylinders. Hyundai spent a few hundred million on the Tau V8, they didn't do that just to put it in the Genesis and not carry anything over to other models.

Ford has a new DOHC V8 coming for the Mustang, F150 and possibly an Ecoboost V8 with over 500 hp for the Shelby GT500. Everyone else (except Chrysler) is spending on R&D, GM has to keep up. Otherwise this will be like 2000-2005 when GM had the 3800 V6/4-speed auto and the imports had more advanced engines/transmissions and stole a lot of market share.

That's a good point. While initial costs of developing a new DOHC V8 might be higher, it might be cheaper in the long run, since a lot could be shared with their DOHC V6s and I4s. Any new technology they use on the V8, could be used in the rest of their DOHC engines, without having to figure out how to adapt the technology between OHC and OHV.

[hyperv6]

Another possible scenario is making the Corvette a twin turbo V6. The GT-R matches a Z06 in a straight line and beats iton the Nurburgring, and the GT-R is heavier and has a back seat. If they want to keep the Vette light and meet CAFE/emissions regs, the V6 may become the standard engine. And if they want to grow sales abroad, that could be a good idea as some countries tax displacement. Although personally, I'd want a V8.

Now wait a minute. You can change a lot of things on the Vette but they learned in the late 70's and early 80's the Vette needs to be and remain a V8. You can change the cams, displacment and a lot of other things but the cylinder count has to remain the same. The Vette demo has pointed this out long ago and the strong response sealed it.

I think they would stop the Vette before they kill the V8.

GM went to lengths in the past of doing two V6 engines before even going to less than 8 pistons. They has a test bed Citation running twin 2.8 V6 engines to test the concept. They just sold that car last spring at Barret Jackson.

They may shrink the present engine but they will not remove two pistons.

Edited November 20, 2009 by hyperv6

[Robert Hall]

A lighter base 'Vette w/ the 3.6 making 325hp or so could be quite tasty, though.

[regfootball]

GM halfassed the twin dual cam, everyone knows that. they took a pushrod block design and tried to convert to OHC. it was a cheap and ineffective approach thats only purpose to GM was to be able to have some manufacturing commonality.

hyperv6, i am not exactly sure why you are assuming that GM has to develop an engine that will be shared in trucks and cars. that question should be asked. and even then, it doesn't necessarily automatically validate a pushrod approach either. trucks do not have the size restrictions or weight restrictions. in fact, the case could be argued that an iron block motor makes more sense in a pickup. but you certainly wouldn't want an iron block engine in a passenger car. it defeats the purpose of making it lighter for performance. the engine mission for a truck and corvette are vastly different. so its entirely appropriate to ask how the passenger car v8 at GM for the next 15 years will be different than the truck engine and how best to accommodate that.

it also has to accommodate tech like HCCi etc. that GM is developing and wants to roll out this tech on all their engines on a modular basis. if engineering uses resources to design a new technology or system for all its powertrains globally, they will want to apply that tech to as many cars and engines with little adaptation as possible. example, notice the streamlined approach with ecoboost.

the point about GLOBAL is the thing. how can GM justify any type of 'North America only' approach for any of its powertrain programs anymore since the B-day?

remember the premise of the original northstar? 2 in line fours were supposed to make a v8, of course whether they followed through on that is not sure. all the design of the bore centers, bore stroke, heads, intake etc. can presumably be amortized commonly, along with new tech like DI, VVT, Hcci, all that. Now that GM is really forcing the global issue it becomes a question if the markets outside the US recognize the benefits of or even want to deal with large pushrod motors. Its entirely possible that GM will be forced to leave the CTSv and Corvette as the last bastion of pushrods and be forced to have bandaid engineering for the next ten years because they will want to spend their R&D budget on other global engine applications.

or the reverse may be true, they may see the Vette is a way to get money to fund an all new line of v8's at which point you are back to, well then we need to use this in other products and those products do not want to be pushrod motors outside of north america either.

as an example. lets say opel decides to offer a large RWD based sedan variant as a flagship model and to help co develop a new cadillac flagship. the germans won't accept a pushrod motor into their market and let it be successful.

Edited November 20, 2009 by regfootball

[hyperv6]

Those red wires against the firewall connect to foot long plastic housings that slide deep past the camshaft heads into the block. If the entire engine was an all-new design from the block on up, then this issue may not have been so significant. This wasn't an all-new design, but had carry-over parts similar to the 3.1 L pushrod. GM worked with what they had available without having to go from scratch because, well, they couldn't.

Yes this was not a clean sheet of paper engine. It share much with the 60 degree push rod engines heritage. I recall many issue on these engins when they came out and GM often replaced them vs letting the dealers repair them.

Some Fiero guys are still loyal to these even though they were never reliable or easy to get parts for today. This was one of the engines the Fiero had planned for it and it just never came to be. The 1990 Prototype has one in it at the GM collection.

Also factored into to this. This engine was planned from what I was told for the GM 80 FWD F body replacment that died in development. They were looking to use it in this car and when it was canceled it left it with no where to go sinc the Fiero also dies soon after.

I often wondered if this engine just dis not work well because it was just never intended for the early W cars. It was kind of like an engine with no where to go.

I have had many people I know who had these at work with intake and head gasket problems.

[CaddyXLR-V]

A lighter base 'Vette w/ the 3.6 making 325hp or so could be quite tasty, though.

2800lbs and 325hp would be fun. The traditionalists wouldn't allow it though.

[Robert Hall]

2800lbs and 325hp would be fun. The traditionalists wouldn't allow it though.

'tradition' can only go so far, GM has to be able to evolve their products and move forward. With the demise of the Kappas, GM has no small sports car now..something like this could be a good intro model for Corvette.

Edited November 20, 2009 by Cubical-aka-Moltar

[hyperv6]

GM halfassed the twin dual cam, everyone knows that. they took a pushrod block design and tried to convert to OHC. it was a cheap and ineffective approach thats only purpose to GM was to be able to have some manufacturing commonality.

hyperv6, i am not exactly sure why you are assuming that GM has to develop an engine that will be shared in trucks and cars. that question should be asked. and even then, it doesn't necessarily automatically validate a pushrod approach either. trucks do not have the size restrictions or weight restrictions. in fact, the case could be argued that an iron block motor makes more sense in a pickup. but you certainly wouldn't want an iron block engine in a passenger car. it defeats the purpose of making it lighter for performance. the engine mission for a truck and corvette are vastly different. so its entirely appropriate to ask how the passenger car v8 at GM for the next 15 years will be different than the truck engine and how best to accommodate that.

it also has to accommodate tech like HCCi etc. that GM is developing and wants to roll out this tech on all their engines on a modular basis. if engineering uses resources to design a new technology or system for all its powertrains globally, they will want to apply that tech to as many cars and engines with little adaptation as possible. example, notice the streamlined approach with ecoboost.

the point about GLOBAL is the thing. how can GM justify any type of 'North America only' approach for any of its powertrain programs anymore since the B-day?

remember the premise of the original northstar? 2 in line fours were supposed to make a v8, of course whether they followed through on that is not sure. all the design of the bore centers, bore stroke, heads, intake etc. can presumably be amortized commonly, along with new tech like DI, VVT, Hcci, all that. Now that GM is really forcing the global issue it becomes a question if the markets outside the US recognize the benefits of or even want to deal with large pushrod motors. Its entirely possible that GM will be forced to leave the CTSv and Corvette as the last bastion of pushrods and be forced to have bandaid engineering for the next ten years because they will want to spend their R&D budget on other global engine applications.

or the reverse may be true, they may see the Vette is a way to get money to fund an all new line of v8's at which point you are back to, well then we need to use this in other products and those products do not want to be pushrod motors outside of north america either.

as an example. lets say opel decides to offer a large RWD based sedan variant as a flagship model and to help co develop a new cadillac flagship. the germans won't accept a pushrod motor into their market and let it be successful.

I agree with just about all of this.

The only reason I say that the next engine 2 or 4 valve needs to be the shared is that between the cost and the fact the V8 will be in a much more limited use than ever. The fact you combine the use with 3 cars will give you more money and support to build a much better engine.

It would be much like today. The base the new engine is designed on is what we are looking at but it would still be taylored for each application.

Improvment in efficency is primary. But we also need refinment for Cadillac that also would benefit the other lines as well as performance for the Vette that would help the others.

Trucks are in need of improved mileage if you plan to keep them selling in great numbers. That is the money maker so at this point it will be designed for the truck as it is now and then changed to work in the other cars. Let face it, if the truck V8 left today the Vette would also lose it too. Like it or not the Vette for years has had to rely on other GM products and only the C5 and 6 got more specialized but still shared the base engine design.

The global idea can be big. Just based on where and how the engine will be sold will effect what it is. The question is where will GM sell it? Europe is getting smaller with many cars and Cadillac has yet to impact the market. Odd of Opel selling a V8 are slim.

Holden I do not think they care. Aussies just want power. China the rich just ride and the poor walk or have 4 cylinder cars. At this point many there will take what they can get. They have not had cars long enough to get too picky yet.

So the primary V8 market will be North America and the truck line will be the biggest user.

The question also comes in what Dodge or Fiat will do with their V8. Does GM want to be the last push rod standing in a sea of higher tech V8 trucks? I do not see Fiat not changing the V8 in time. The Dodge push rod will live on for a while as they have too many other issues to deal with for now.

There are a lot of things on the table here and GM is going to just have to wade through it. Out arguments one way or the other is just the surface of this issue.

[hyperv6]

'tradition' can only go so far, GM has to be able to evolve their products and move forward. With the demise of the Kappas, GM has no small sports car now..something like this could be a good intro model for Corvette.

From what Tom Wallace stated last winter it is a given the C7 will be a major drop in size and weight.

Also there was talk of some kind of V8 in the 4 Liter plus area.

Wallace pointed out that the engine may be down on performance a little the performace of a lighter car would improve the Vette in all areas of Braking. Accleration, Handling and mileage.

I would not expect Kappa small. The car will be a little bigger. But with the Vettes higher base price than the Kappa the weight could be held to 2800-2900 pounds.

As long as peformance is retaind or enhanced you can go smaller on the car or the engine but it has to remain a V8.

The Book Inside the Corvette By Dave McClellan points this out and what GM learned from their owners over the years. If some here think they would hate to lose push rods just watch what they do if you lose 2 cylinders.

[Drew Dowdell]

GM may have half assed the TwinCam V6, but that engine was years ahead of anything the Japanese and VW were doing. The Twincam was 215hp in 1990, Honda didn't break the 200hp barrier till 2004 and didn't beat the Twincam's 215 torque until 2008. Toyota and VW didn't get around to it till 2004 and 2006 respectively.

Even Nissan's much vaunted VQ V6 took 10 years to overcome the Twincam in power.

So, yea the alternator and spark plugs are a bit tough to change, but the Twincam had it's benefits also.

[CaddyXLR-V]

GM may have half assed the TwinCam V6, but that engine was years ahead of anything the Japanese and VW were doing. The Twincam was 215hp in 1990, Honda didn't break the 200hp barrier till 2004 and didn't beat the Twincam's 215 torque until 2008. Toyota and VW didn't get around to it till 2004 and 2006 respectively.

Even Nissan's much vaunted VQ V6 took 10 years to overcome the Twincam in power.

So, yea the alternator and spark plugs are a bit tough to change, but the Twincam had it's benefits also.

Actually Nissan was making was getting 222hp out of their 3L in the 300zx in NA form, so I wouldn't really say they were behind.

[Robert Hall]

The global idea can be big. Just based on where and how the engine will be sold will effect what it is. The question is where will GM sell it? Europe is getting smaller with many cars and Cadillac has yet to impact the market. Odd of Opel selling a V8 are slim.

Since Opel didn't continue the Omega, I don't see them going back to a large V8 model. Larger mainstream brand models from Ford, Opel and Vauxhall died out in the 90s in Europe. It seems only the premium brands can support cars larger than the Mondeo/Vectra/Insignia in the European market.

Outside of NA, about the only market for big American trucks seems to be some South American markets and the Middle East. Have no idea the volume in such markets.

As far as V8 RWD American style full size sedans, it seems Australia, the Middle East and China are the markets for these, i.e. w/ Holden based models and Ford in Australia (do they sell a LHD Falcon anywhere?).

Other than Chrysler and potentially some Holden-based imports, I don't see a lot of future for them here, since GM and Ford have largely abandoned them for FWD models, as have the public...

Other than the Charger, 300, Challenger, Mustang, Camaro, CTS-v, and Corvette there won't be any RWD V8 cars made by the US 3 after the Panthers go away in '11, unless GM really does bring some Holden-based models like the Caprice PPV.

Edited November 20, 2009 by Cubical-aka-Moltar

[regfootball]

GM may have half assed the TwinCam V6, but that engine was years ahead of anything the Japanese and VW were doing. The Twincam was 215hp in 1990, Honda didn't break the 200hp barrier till 2004 and didn't beat the Twincam's 215 torque until 2008. Toyota and VW didn't get around to it till 2004 and 2006 respectively.

Even Nissan's much vaunted VQ V6 took 10 years to overcome the Twincam in power.

So, yea the alternator and spark plugs are a bit tough to change, but the Twincam had it's benefits also.

funny you use the word 'break' when mentioning the twin dual cam......

my 89 SHO motor was far better than the twin dual cam. if i still had that car today, the engine would still be running flawlessly, burning no oil, no lost performance. when i think of 'break' with that engine, i think of breaking traction in lots of wheelspin. even bach then gm didn't make the superior v6.

[regfootball]

From what Tom Wallace stated last winter it is a given the C7 will be a major drop in size and weight.

Also there was talk of some kind of V8 in the 4 Liter plus area.

Wallace pointed out that the engine may be down on performance a little the performace of a lighter car would improve the Vette in all areas of Braking. Accleration, Handling and mileage.

I would not expect Kappa small. The car will be a little bigger. But with the Vettes higher base price than the Kappa the weight could be held to 2800-2900 pounds.

As long as peformance is retaind or enhanced you can go smaller on the car or the engine but it has to remain a V8.

The Book Inside the Corvette By Dave McClellan points this out and what GM learned from their owners over the years. If some here think they would hate to lose push rods just watch what they do if you lose 2 cylinders.

think of Lotus Evora light.....with a standard toyota v6 it goes pretty well. imagine that with twin turbo. i see the lotus as sort of poster child of where sports cars are headed.

a car midway between a kappa and current corvette.......actually if you are down to 2900 or 2800 pounds, why not just make a balls out inline engine, a four, if packaging is a primary driver? turbo the snot out of a 2.5 four and get the car down to 2500 pounds and lets see what happens. with an inline four, your package is much smaller than that 'small' v8.

[Robert Hall]

with an inline four, your package is much smaller than that 'small' v8.

Width, yes..the length of an inline four is pretty much the same as a V8, though.

I'd love to see a Chevy Kappa w/ a turbo 4 (Solstice GXP), but badging it as a Corvette would freak the fogeys...maybe find another name for a small Chevy sports car.

[Drew Dowdell]

funny you use the word 'break' when mentioning the twin dual cam......

my 89 SHO motor was far better than the twin dual cam. if i still had that car today, the engine would still be running flawlessly, burning no oil, no lost performance. when i think of 'break' with that engine, i think of breaking traction in lots of wheelspin. even bach then gm didn't make the superior v6.

I'm not even suggesting that the TwinDualCam was the best engine on the market. I'm just saying that it was 10 - 15 years ahead of the imports in performance. I had a TDC in my Cutlass it ran great. I had the timing belt start to go right around it's scheduled replacement time and had it fixed prior to it snapping. The alternator went out twice but the second time was due to a faulty replacement job (the first replacement alternator didn't have the heat venting replaced during the install). I could easily light up the front tires in 1st and chirp them up to 3rd.

[regfootball]

Width, yes..the length of an inline four is pretty much the same as a V8, though.

I'd love to see a Chevy Kappa w/ a turbo 4 (Solstice GXP), but badging it as a Corvette would freak the fogeys...maybe find another name for a small Chevy sports car.

the fogeys are dying off soon. their 401ks tanked and they will leaving the workforce and buying avalons anyways

[regfootball]

I'm not even suggesting that the TwinDualCam was the best engine on the market. I'm just saying that it was 10 - 15 years ahead of the imports in performance. I had a TDC in my Cutlass it ran great. I had the timing belt start to go right around it's scheduled replacement time and had it fixed prior to it snapping. The alternator went out twice but the second time was due to a faulty replacement job (the first replacement alternator didn't have the heat venting replaced during the install). I could easily light up the front tires in 1st and chirp them up to 3rd.

tdc had performance. gm should have invested more in seeing the progress of that through.

anyone think the next vette gets AWD option? 500hp+featherweight = can't keep it on the track

[SAmadei]

Width, yes..the length of an inline four is pretty much the same as a V8, though.

I'd love to see a Chevy Kappa w/ a turbo 4 (Solstice GXP), but badging it as a Corvette would freak the fogeys...maybe find another name for a small Chevy sports car.

Maybe GM comes up with something akin to the VW W8... or a 1/2 W8 4 cylinder. I want to call this a 'U' engine, but that would be something different.

Edit: I guess it would be a very narrow angle V4.

Edited November 21, 2009 by SAmadei

[hyperv6]

think of Lotus Evora light.....with a standard toyota v6 it goes pretty well. imagine that with twin turbo. i see the lotus as sort of poster child of where sports cars are headed.

a car midway between a kappa and current corvette.......actually if you are down to 2900 or 2800 pounds, why not just make a balls out inline engine, a four, if packaging is a primary driver? turbo the snot out of a 2.5 four and get the car down to 2500 pounds and lets see what happens. with an inline four, your package is much smaller than that 'small' v8.

I would love to see a GM do a car like that but it is well down on the to do list.

All cars are going to get lighter not just sports cars. GM and Mazda both have stated cars are too heavy and even Mazda is looking to remove 200 pounds ASAP from each of their cars.

Now if you want to do this as a Cadillac or Buick you may have something if it could be done cost effective. It has to pay the rent or they will not build it. I would like to see a light weight Buick 2+2 coupe come to life with a back seat and 350 HP at 2900 pounds. Kind of a Solstice coupe that you can really use for daily driving without the weird RX8 kind of a back end.

As for the Vette guys they want 8 Cylinders like a Harley guy wants a V twin. You give them a 4 and no matter the power you will lose them. That would only increase the value of the C4.

The present Ecotec has a lot of room to gain power. As the LNF sits now it can go to 400 HP with no changes internally after 400 I think they recomend changing pistons. With minor changes it can go to 500 HP. The GM Ecotec performance book out lines what the engine can do and it will go a long way. He was very excited to work with this and the 3.6 as he was getting 2,000 easy in race trim. I am in no way saying these were stock but it shows what can be done but you would be suprised how many stock parts were used in these engines. It showed me how much could be done with the stock engine yet. I was not suprised with the power the present LNF has nor will be shocked to see more in the future.

Think of the Eco as the 265 SBC was in 1955 only without oil ring issue that made the first SBC use oil. The Eco is only at the begining of a long and more powerful future.

[hyperv6]

tdc had performance. gm should have invested more in seeing the progress of that through.

anyone think the next vette gets AWD option? 500hp+featherweight = can't keep it on the track

Electronics are keeping the ZR1 on track now.

Any time you bring in AWD the questions of weight and how much power to run it. Audi has done well there many others have not. AWD is nice but it has to be done right and durable.

[hyperv6]

Here is the story last January on the C7. HP per pound was a point driven home. Also note a Hybrid could be in the Vettes future was stated last month. Word is a mid engine is done and Autoweek wanted to speculate a C7 would be delayed or gone. [Note No one else has stated that].

Here is what Wallace hinted at what they were looking at. Some may have seen this but some may not have.

Over the last few years, the mantra at Corvette has been more performance, more horsepower. But the passage of the new energy bill that raises the CAFE standards to an average of 35 mpg will undoubtedly force GM's engineers to rethink performance while pursuing economy first. The results will be a lighter, greener Corvette that will not only survive the 35 mpg standard, but should thrive in it as well.

The standard Corvette coupe and convertible models already get a highly respectable 28 mpg highway average despite being powered by the 6.2 liter 430 hp LS3. With its fiberglass panels and hydroformed aluminum frame, the current Corvette already weighs in at a lean 3200 pounds. According to Tom Wallace, GM's Performance Vehicle Line Executive, the future Corvette will be a sports car where fuel economy and a reduced carbon footprint can coexist with performance as long as engineers pay attention to the ever important weight to horsepower ratio.

Wallace won't talk specifics about the C7 Corvette, but he told Automotive News that if the Corvette's weight was dropped 300 to 400 pounds and was powered by a 4.7 Liter V8 with about 150 less hp than the current LS3, the weight to horsepower ratio is essentially the same as the current standard C6 Corvette.

While the Corvette ZR1 makes extensive use of carbon fiber as a weight saving material, the cost is currently prohibitive in the standard models. But that could change by the time the C7 is developed.

It's also possible that by the year 2012 when the new C7 Corvette is expected that we will see the next generation of fuel efficient engines that utilize both gasoline and ethanol. With the trickle-down effect that Corvette Racing has on its regular production-bred siblings, its a natural evolution for there to be an E85 powered Corvette coming directly from the assembly plant at Bowling Green. Corvette Racing tells us that ethanol based fuel has a higher octane rating so the combination of the new engines powered by ethanol combined with a lighter body may get Corvette close to the 35 mpg highway average.

Two other factors help Corvette as well. First, the amount of Corvettes produced in recent years averages roughly 35,000 cars compared to the nearly 4 million GM sells domestically, so the impact of the Corvette's highway MPG figure is smaller than that of one of GM's mass-produced vehicles. Secondly, GM's investment in alternative fuel solutions and new products like the Chevy Volt are likely to increase the automaker's average significantly if the market is there to support them.

Corvette enthusiasts may have to swallow the reduced horsepower pill like we had to with the C3 Corvettes. The good news is that unlike the Seventies, GM won't simply cut performance to increase mileage standards. Performance will always be one of the governing covenants of the Corvette, and with the looming changes on the horizon, there will be room for a green Corvette.

Just food for thought. Our debate here just over valves may not come close to some of the coming changes we may see in the car.

Edited November 21, 2009 by hyperv6

[smk4565]

2800lbs and 325hp would be fun. The traditionalists wouldn't allow it though.

GM cars always get heavier though, and the Vette is around 3300 pounds now, even if they hold it to 3300, I thought the V6 could be a way to keep weight down around 3200-3300 lbs. But I was thinking twin turbo V6 with more like 380 hp, and turbo engines can make peak torque around 1800 rpm so off the line it could be quite good.

I'd rather have a V8, I am just saying the twin turbo V6 is an option to be explored. Low weight makes for good sports cars.

[balthazar]

>>"GM cars always get heavier though"<<

Only GM ?? Back in the day the 3-series used to weigh 2500 or thereabouts, it gained 1000 lbs! How bad does the Accord punish the scale vs. years ago ?

Everything gains weight thru to today, not just GM.

Cars are already half plastic as it is, with aluminum powertrains & wheels and chopped-down proportions and they STILL weigh 3600-4000 lbs. Electronics & air bags aren't made of cotton candy, and they aren't going anywhere. Don't hold your breath expecting a 3800-lbs car to drop 500 lbs- ain't gonna happen.

[regfootball]

Here is the story last January on the C7. HP per pound was a point driven home. Also note a Hybrid could be in the Vettes future was stated last month. Word is a mid engine is done and Autoweek wanted to speculate a C7 would be delayed or gone. [Note No one else has stated that].

Here is what Wallace hinted at what they were looking at. Some may have seen this but some may not have.

Over the last few years, the mantra at Corvette has been more performance, more horsepower. But the passage of the new energy bill that raises the CAFE standards to an average of 35 mpg will undoubtedly force GM's engineers to rethink performance while pursuing economy first. The results will be a lighter, greener Corvette that will not only survive the 35 mpg standard, but should thrive in it as well.

The standard Corvette coupe and convertible models already get a highly respectable 28 mpg highway average despite being powered by the 6.2 liter 430 hp LS3. With its fiberglass panels and hydroformed aluminum frame, the current Corvette already weighs in at a lean 3200 pounds. According to Tom Wallace, GM's Performance Vehicle Line Executive, the future Corvette will be a sports car where fuel economy and a reduced carbon footprint can coexist with performance as long as engineers pay attention to the ever important weight to horsepower ratio.

Wallace won't talk specifics about the C7 Corvette, but he told Automotive News that if the Corvette's weight was dropped 300 to 400 pounds and was powered by a 4.7 Liter V8 with about 150 less hp than the current LS3, the weight to horsepower ratio is essentially the same as the current standard C6 Corvette.

While the Corvette ZR1 makes extensive use of carbon fiber as a weight saving material, the cost is currently prohibitive in the standard models. But that could change by the time the C7 is developed.

It's also possible that by the year 2012 when the new C7 Corvette is expected that we will see the next generation of fuel efficient engines that utilize both gasoline and ethanol. With the trickle-down effect that Corvette Racing has on its regular production-bred siblings, its a natural evolution for there to be an E85 powered Corvette coming directly from the assembly plant at Bowling Green. Corvette Racing tells us that ethanol based fuel has a higher octane rating so the combination of the new engines powered by ethanol combined with a lighter body may get Corvette close to the 35 mpg highway average.

Two other factors help Corvette as well. First, the amount of Corvettes produced in recent years averages roughly 35,000 cars compared to the nearly 4 million GM sells domestically, so the impact of the Corvette's highway MPG figure is smaller than that of one of GM's mass-produced vehicles. Secondly, GM's investment in alternative fuel solutions and new products like the Chevy Volt are likely to increase the automaker's average significantly if the market is there to support them.

Corvette enthusiasts may have to swallow the reduced horsepower pill like we had to with the C3 Corvettes. The good news is that unlike the Seventies, GM won't simply cut performance to increase mileage standards. Performance will always be one of the governing covenants of the Corvette, and with the looming changes on the horizon, there will be room for a green Corvette.

Just food for thought. Our debate here just over valves may not come close to some of the coming changes we may see in the car.

GM has to build corvettes in that volume to keep them alive.

now, the part that gets interesting is what percent are base powertrains. if 2/3 of them are, then lets say at least 2/3 of them or maybe 25,000 of them are base models. unless they stick with the current motor, they will not develop an entirely new motor for it unless they plan to use it for like 8 years......8 x 25,000 = 200,000 and then in that case MAYBE they can do it.

that still leaves you with 10k sales a year that are uplevel and then its a question are they just 'tuned' and 'forcefed' versions of the base motor?

again, unless you think you can get 20k more cash vs the base model to pay for this.....I am already seeing ads for Z06 vettes new for 60k or 20k off sticker.

Lutz hinting at a twin turbo 3.6 REALLY makes me wonder, if the TT isn't being considered for a SLEW of GM's uplevel niche products.

Ford is applying the 3.5 ecoboost over several models. probably at least 8 models after all is said and done. if they sell 5k of each of those 8 models a year, that's 40k and do it for 5 years, that is 200k which pays for the ecoboost over the stock 3.5 and is much cheaper than developing an all new engine.

where GM may go with a similar appraoch is to take their 3.6 and TT it and put it in the CTS, ATS, SRX, Camaro, (Corvette) some buick, a host of models. that might delay the need to develop a new v8. but i think at some point GM does do a new v8 for passenger use and then it becomes which vehicles do they put it in.

I think it goes in the new flagship cadillac, and the corvette. if you think about it, just between those two cars they can make a business case for 40,000 engines a year base. if this is a base corvette and caddy flagship motor, it won't have to be ultra exotic. as an example, it probably just has to be a notch or two above the hyundai genesis in power. so perhaps a 380hp 8 cylinder in a lighter corvette and as a second level flagship caddy, i think they could make it work. and maybe it even does see duty in light passenger trucks. maybe it even makes it in the commodore / caprice in like 2014 also. Then, by adding a twin turbo setup, maybe the thing can be tuned to 520 hp or something without much fuss.

maybe the next vette has an 'entry level' 340-350ho v6 (like a harley 883 is entry level) to compete with the boxster, and then the bulk of the cars get a typical v8, and the top end is the force fed v8.

Does Lotus get a hand in GM's engine design these days still?

[hyperv6]

I jumped over to a Vette site to see what they were expecting or willing to accept.

I was suprised to see most are already expecting a smaller lighter and less powerful car. But it would remain just as fast.

Keeping the same engine as a 5.5 DI engine was tossed around.

DOHC was something many would like to see. As well as a Superchager or Twin Turbo.

The shocker was that a 3.6 DOHC Twin Turbo was brought up and many said they would like to see it.

The forum had many ideas and suprisingly many were willing to accept change. This often is a group that seldom embraced change.

Some might want to check around and see what other Vette forums are saying. While not all these guys are Smokey Yunick they are the ones buying the car. I am sure GM is taking in some of what they are asking or saying.

One thing for sure when the C7 appears half will love it and half will hate it. Every C change goes this way at the start.

[hyperv6]

GM has to build corvettes in that volume to keep them alive.

now, the part that gets interesting is what percent are base powertrains. if 2/3 of them are, then lets say at least 2/3 of them or maybe 25,000 of them are base models. unless they stick with the current motor, they will not develop an entirely new motor for it unless they plan to use it for like 8 years......8 x 25,000 = 200,000 and then in that case MAYBE they can do it.

that still leaves you with 10k sales a year that are uplevel and then its a question are they just 'tuned' and 'forcefed' versions of the base motor?

again, unless you think you can get 20k more cash vs the base model to pay for this.....I am already seeing ads for Z06 vettes new for 60k or 20k off sticker.

Lutz hinting at a twin turbo 3.6 REALLY makes me wonder, if the TT isn't being considered for a SLEW of GM's uplevel niche products.

Ford is applying the 3.5 ecoboost over several models. probably at least 8 models after all is said and done. if they sell 5k of each of those 8 models a year, that's 40k and do it for 5 years, that is 200k which pays for the ecoboost over the stock 3.5 and is much cheaper than developing an all new engine.

where GM may go with a similar appraoch is to take their 3.6 and TT it and put it in the CTS, ATS, SRX, Camaro, (Corvette) some buick, a host of models. that might delay the need to develop a new v8. but i think at some point GM does do a new v8 for passenger use and then it becomes which vehicles do they put it in.

I think it goes in the new flagship cadillac, and the corvette. if you think about it, just between those two cars they can make a business case for 40,000 engines a year base. if this is a base corvette and caddy flagship motor, it won't have to be ultra exotic. as an example, it probably just has to be a notch or two above the hyundai genesis in power. so perhaps a 380hp 8 cylinder in a lighter corvette and as a second level flagship caddy, i think they could make it work. and maybe it even does see duty in light passenger trucks. maybe it even makes it in the commodore / caprice in like 2014 also. Then, by adding a twin turbo setup, maybe the thing can be tuned to 520 hp or something without much fuss.

maybe the next vette has an 'entry level' 340-350ho v6 (like a harley 883 is entry level) to compete with the boxster, and then the bulk of the cars get a typical v8, and the top end is the force fed v8.

Does Lotus get a hand in GM's engine design these days still?

The Turbo V6 is coming to GM just when. The Leno car was just a hint on the future.

The one key no matter what they do is as long as it has power and is as fast or faster the Vette will be accpeted even with low tech. I just worry for the future will the engine be viable in the changes the Goverment will toss at it in the future.

I also note they have really been pushing the Grand Sport. It this GM's way to push the Base Vette more upscale? Will this become the new base? I though I saw they expect it to be over half the sales.

Lotus will get a hand if GM pays them. The one trade off in the lotus cars is they are light but pay a price for it in many areas. The Elise is mostly a stripped down car. The Exige is a stripped down racer for the street. While I love these cars the general public still want the toys. I work with a guy with a new Exige and few people would accpect a car like that for that price. It does not even have a rear window. It is for the person who is willing to do track time where most Vettes never hit the track.

So you have to keep the toys and still lose the weight.

[dwightlooi]

I know I may be hijacking this thread but I am interested now in some expert information from dwightlooi. So with the disadvantages to a gasoline turbo. What makes a diesel turbo better? If it is better?

Oh well... that's a whole other topic, but here's the long summary:-

(1) Why Diesels rock.

Diesel fuel does not carry more energy than gasoline. Diesel has an energy density of 46,300 kJ/kg vs 46,500 kJ/kg for gasoline (about the same). Even though diesel fuel is denser 0.85kg/liter vs 0.72 kg/liter for gasoline so the same mass of diesel fuel can be stored in 16% smaller a tank, that's something which may matter in a rocket or aircraft but not really tangible in a car.

Diesel is better that gasoline mainly in two ways and it's all due to the way the diesel engine operates. The Diesel cycle (as opposed to the Otto cycle gasoline engine) does not have a spark plug and does not regulate air intake with a throttle body. A diesel engine compresses the air-fuel mixture to the tune of about 22:1. The mixture auto-ignites. The uniform burning from homogeneous auto-ignition and the high compression ratio enhances efficiency. In addition, a diesel engine basically suck in as much air as it can with no throttle regulation. Power output is governed simply by the amount of fuel introduced to the mixture. Diesel engines run very lean at idle, going richer and richer as you advance the gas pedal. The lack of a throttle butterfly reduces pumping losses and increases efficiency.

(2) Why Diesels suck.

Diesel engines plain out make less power than its gasoline counterparts all else being equal. An average naturally aspirated diesel engine of 2 liters may make about 75hp compared to 140hp in a gas engine.

Ignition in a Diesel engine happens automatically from the mixture being at a certain pressure (hence temperature; pV=nRT) for a given period of time (it is not controllable by spark timing like in gasoline engines). This means that ignition happens too early at low engine speeds, with the mixture combusting before the piston reaches the top its compression stroke. This is why diesel engines knock and clatter at, or near, idle before smoothing out at about 1000~1500 rpms. As revs climb, diesel engines start to lose power as the ignition happens too late into the power stroke as the piston is coming down. If ignition happens at the bottom of the stroke an engine makes zero power, and way before that it starts to make less and less. Somewhere between 3000 and 4000 rpm ignition becomes notably late and diesels start to get noticeably out of breath. Usually by 4000~5000 rpm power falls completely flat which is why diesels have such low red lines. This is not just a characteristic shunned by driving enthusiasts, but also a problem because the narrow rev range means you need a lot of gears in the transmission to keep the engine operating between 1000 and 3500 rpm for instance. Ever wondered why 18-wheel big rig trucks with those massive 16 liter 6-cylinder diesels have 18-speed transmissions? Well, now you know why. Direct injection permits some rudimentary control of the ignition event by basically controlling when fuel is introduced! But this is not the same as precisely timing it with a spark event; it mitigates but does not eliminate the problem.

With knocking and pinging being normal mode of operation, Diesels also need very stout bottom ends. In the old days it means a heavy iron block with big fat rods and journals. Even with today's "high-tech" aluminum diesels the engine is still heavier than a gasoline engine.

Because a diesel engine runs lean at idle and at cruise, while going rich with the advancement of the throttle, it pollutes more in non-carbon related ways. This is particularly a problem during lean conditions (which is most of the time). Lean mixtures burn very hot and with lots of spare oxygen molecules sitting around. That produces lots of oxides of Nitrogen (NO, NO2, etc) which are hazardous to our health. Hence, diesels often need expensive nitrogen storing catalysts or Urea (yes, as in urine) injection to meet contemporary emission standards. In addition, because all the nitrogen storing catalysts are sensitive to degradation by sulfur contaminants, it is also important that sulfur is kept out of the fuel.

(3) How turbochargers make a difference.

Turbos basically help with getting the power density of diesel engines to the level of their naturally aspirated gasoline counterparts. A 2 liter turbo-diesel is now good for 140hp just like a decent 2.0 liter gasoline engine.

Turbo-diesels have the same plumbing and intercooling complexities of force fed gasoline engines. But it has one advantage. The exhaust temperatures tend to be lower on diesel engines. This allows certain technologies like variable vane geometry turbochargers that tend to fail prematurely in gasoline applications to be used successfully in diesel engines. The lower EGT also makes it easier to place the turbocharger and the hot exhaust manifold in the valley of a Vee type engine compared to gasoline engines. The Duramax 6.6 for instance has the turbo in the middle of the engine with the intake plenums on the sides where the exhaust manifolds usually reside.

Edited November 21, 2009 by dwightlooi

[Camino LS6]

The core of this issue is trucks, any new V8 architecture will be created with trucks as the determining factor in the design. It is only through adaptability of a truck-based design that we have V8s for Camaro, Corvette, and CTS-V.

If a new DOHC V8 is ever developed, it will have to cater to truck applications first and foremost. And, it will have to bring one whole hell of alot more than a DOHC configuration to the table to ever be approved.

Remember now, that CAFE functions on the concept of an average and that GM has already made great strides in efficiency in non-V8 applications. Not to mention the efficiency of the current V8s is outstanding to begin with, and weight reduction across the fleet is a main focus. V8 powered cars will improve in efficiency no matter what, and performance in the real world will be maintained via weight reduction and other technology -based advancements.

GM knows how to do this, and they have risen to the challenge every time the bar has been moved. Their V8 technology is not behind the curve at all, and won't be in the future. In fact, if GM had been as good at keeping other aspects of its products as up to date and real-world effective as the V8s have been, they wouldn't be in such a tough spot as they are today.

The elimination of the V8, and the addition of DOHC to it, are not immediate issues for GM. A healthier, profitable, GM may choose to develop a DOHC V8 for premium models some day, but it won't be tomorrow, and it won't supplant the pushrod V8 except in low volume products. The V8 will continue to evolve as it always has, adapting to changing parameters as required.

With all of that said, I do expect to see a reduction in both displacement and output of V8 engines going forward, but with an offset of weight reduction and midigating tech that maintains performance levels.

GM has the best drivetrain folks on the planet who have proven again and again that they can meet whatever requirements are thrown at them. No one does the V8 better than GM - no one.

Edited November 21, 2009 by Camino LS6

[Z-06]

Great last two posts.

Here is a simple math. Collectively GMT900's cater to 1 to 1.2 million vehicles annually. Almost 90% of those are V-8's. That is a lot of V-8 engines to deal with. Trucks need engines with easy fix deal with lot of stress with less moving parts and high reliability. If GM comes with an engine which bunks you will see a lot of GM faithfuls ditching their trucks.

And for truck applications OHV is better than DOHC given the proven technology - remember Tundra's falling CAMS due to excessive load conditions they were put in? Now V-8 cars in GM are about not more than 200,000 annually. Given this math, shortage of money, no significant advantage of DOHC over OHV, room to grow for the OHV with DI it is no brainer that GM has to stick with OHV.

[Camino LS6]

Nice summation, Zo6.

Let's also remember how badly, and expensively, the Tundra failed.

GM can afford no such mistakes.

[Robert Hall]

Nice summation, Zo6.

Let's also remember how badly, and expensively, the Tundra failed.

GM can afford no such mistakes.

Yes, but Ford has been quite successful with OHC truck engines for over a decade now.... Toyota's a niche player(in the full size truck market), Ford has long been the market leader.

Edited November 21, 2009 by Cubical-aka-Moltar

[Camino LS6]

Yes, but Ford has been quite successful with OHC truck engines for over a decade now.... Toyota's a niche player(in the full size truck market), Ford has long been the market leader.

Ford owes its market lead (thin as it is) to the split between Chevy and GMC trucks, not to anything else.

[Robert Hall]

Ford owes its market lead (thin as it is) to the split between Chevy and GMC trucks, not to anything else.

Point is, Ford's success proves OHC engines are applicable to truck applications. OHC V8s are hardly a new technology.

[Camino LS6]

Point is, Ford's success proves OHC engines are applicable to truck applications. OHC V8s are hardly a new technology.

Applicable, yes.

But in no way superior.

Not in power, reliability, nor economy - that crown belongs to GM's pushrod.

Ford developed their DOHC in flush times, and gained no real advantage.

It actually stands as a good exapmle of why GM should not roll the dice - what would it gain?

A wholesale move to DOHC V8s would cost a mint with zero market impact.

[CaddyXLR-V]

Yes, but Ford has been quite successful with OHC truck engines for over a decade now.... Toyota's a niche player(in the full size truck market), Ford has long been the market leader.

Yes, that does seem to be forgotten here. People didn't switch to Chevy when Ford started using SOHC and DOHC in their trucks, so I see no reason why Chevy buyers would switch if the same was done at GM.

I would like to see V8 engines based on both the ecotec and the 3.6L. That would give it a displacement range between 4-4.8L. And if the ecotec can already support a lot of power, imaging what a V8 based off it could handle.

[CaddyXLR-V]

Applicable, yes.

But in no way superior.

Not in power, reliability, nor economy - that crown belongs to GM's pushrod.

Ford developed their DOHC in flush times, and gained no real advantage.

It actually stands as a good exapmle of why GM should not roll the dice - what would it gain?

A wholesale move to DOHC V8s would cost a mint with zero market impact.

Commonality between their DOHC V6s and their DOHC V8s

[SAmadei]

With all of that said, I do expect to see a reduction in both displacement and output of V8 engines going forward, but with an offset of weight reduction and midigating tech that maintains performance levels.

I hope that GM doesn't waste too much money on creating a reduced displacement/output V8, as I'm not sure its going to fly. First, a low output V8 has the V6 nipping at its heels, which is cheaper due to its higher production. Next, customers have unrealistic expectations... it won't have the torque or response people expect. This will be a replay of the Poncho 301/265, Olds 307, Chevy 305/267 days... not what GM needs to bolster the image.

Sure, in 2010, GM could use the magic of DI and computers to make a 265 a workable engine, but its going to be compared to the LS2/LS3/L76.

I feel displacements are currently 'right-sized' at about 350 inches, for weight, power, efficiency, and customer expections. And further technology will make them even more efficient.

Since many here are banking on future technological improvements to make the Volt workable, I'm going to bank on metallurgy, carbon fiber, ceramics and technology to continue to make the V8 incredibly light and efficient... perhaps nanotechnology using carbon fiber in ultrathin steel or aluminum castings or a true displacement on demand that actually decouples the rear half of the engine for a super efficient mode. Just dreaming...

[CaddyXLR-V]

I hope that GM doesn't waste too much money on creating a reduced displacement/output V8, as I'm not sure its going to fly. First, a low output V8 has the V6 nipping at its heels, which is cheaper due to its higher production. Next, customers have unrealistic expectations... it won't have the torque or response people expect. This will be a replay of the Poncho 301/265, Olds 307, Chevy 305/267 days... not what GM needs to bolster the image.

Sure, in 2010, GM could use the magic of DI and computers to make a 265 a workable engine, but its going to be compared to the LS2/LS3/L76.

I feel displacements are currently 'right-sized' at about 350 inches, for weight, power, efficiency, and customer expections. And further technology will make them even more efficient.

Since many here are banking on future technological improvements to make the Volt workable, I'm going to bank on metallurgy, carbon fiber, ceramics and technology to continue to make the V8 incredibly light and efficient... perhaps nanotechnology using carbon fiber in ultrathin steel or aluminum castings or a true displacement on demand that actually decouples the rear half of the engine for a super efficient mode. Just dreaming...

a 4.8L based on the 3.6L in the CTS, with the same hp/l, would have about 405hp. If they made a turbo version based on the 2.0 I4, they could make over 520hp from 4L. I think they would make enough power to make people happy.

[Camino LS6]

Yes, that does seem to be forgotten here. People didn't switch to Chevy when Ford started using SOHC and DOHC in their trucks, so I see no reason why Chevy buyers would switch if the same was done at GM.

I would like to see V8 engines based on both the ecotec and the 3.6L. That would give it a displacement range between 4-4.8L. And if the ecotec can already support a lot of power, imaging what a V8 based off it could handle.

And no one switched to Ford when they went DOHC either, in fact the Silverado has been endangering Ford's "sales lead" increasingly without the help of GMC's numbers. No advantage for GM is in the offing by switching to DOHC in trucks (quite the opposite, actually). Huge risk for no reward.

GM's trucks are already more powerful and efficient than Ford's, ther is just no case to be made for a switch.

[CaddyXLR-V]

And no one switched to Ford when they went DOHC either, in fact the Silverado has been endangering Ford's "sales lead" increasingly without the help of GMC's numbers. No advantage for GM is in the offing by switching to DOHC in trucks (quite the opposite, actually). Huge risk for no reward.

GM's trucks are already more powerful and efficient than Ford's, ther is just no case to be made for a switch.

Well Ford doesn't exactly make the most efficient engines either. Their 5.0L OHV engine was horrible on gas. Our Explorer never got over 14 mpg. A DOHC V8 could share parts and technology with the V6s. While GM says they can use VVT and other technology on their OHV engines, they haven't done it yet. They have with their V6s. They have VVT and DI on multiple DOHC engines now. They wont need to waste the time and money figuring out how to adapt those technologies to OHV engines. And adding those new technologies to OHV might not be as reliable, since no one has done it before. They already spent the time and money developing them for the DOHC V6s.

It creates twice as much work. Instead of developing it once and using it on all their engines, they have to develop it twice.

Edited November 21, 2009 by CaddyXLR-V

[Camino LS6]

I hope that GM doesn't waste too much money on creating a reduced displacement/output V8, as I'm not sure its going to fly. First, a low output V8 has the V6 nipping at its heels, which is cheaper due to its higher production. Next, customers have unrealistic expectations... it won't have the torque or response people expect. This will be a replay of the Poncho 301/265, Olds 307, Chevy 305/267 days... not what GM needs to bolster the image.

Sure, in 2010, GM could use the magic of DI and computers to make a 265 a workable engine, but its going to be compared to the LS2/LS3/L76.

I feel displacements are currently 'right-sized' at about 350 inches, for weight, power, efficiency, and customer expections. And further technology will make them even more efficient.

Since many here are banking on future technological improvements to make the Volt workable, I'm going to bank on metallurgy, carbon fiber, ceramics and technology to continue to make the V8 incredibly light and efficient... perhaps nanotechnology using carbon fiber in ultrathin steel or aluminum castings or a true displacement on demand that actually decouples the rear half of the engine for a super efficient mode. Just dreaming...

The risk is there, but it is far from the same situation as the late 70s. This time around, weak, detuned, engines won't simply be dropped into the same heavy car designed for far greater output. As long as performance is maintained (or increased) in a given model, GM will look like a hero.

[Camino LS6]

Well Ford doesn't exactly make the most efficient engines either. Their 5.0L OHV engine was horrible on gas. Our Explorer never got over 14 mpg. A DOHC V8 could share parts and technology with the V6s. While GM says they can use VVT and other technology on their OHV engines, they haven't done it yet. They have with their V6s. They have VVT and DI on multiple DOHC engines now. They wont need to waste the time and money figuring out how to adapt those technologies to OHV engines. And adding those new technologies to OHV might not be as reliable, since no one has done it before. They already spent the time and money developing them for the DOHC V6s.

We will have to wait and see how the tech is applied to the existing engines. What you propose would be far more expensive, and risky than advancing the LS series.

I have no doubt that when/if the LS V8s can no longer be on a par or better than another architecture, they will be replaced. The fact remains that they are more than competitive today, and have great potential for further develpoment. It simply doesn't make sense to abandon such a successful format at this time. When no more potential for the smallblock was there to be had the LS was born. Until that fate compromises the LS, I expect to see GM evolving it over time. Such a progression is what reliability is made of.

DOHC will never be the determining factor in a change to a new V8, someday it may "come with the package", but that's about it. Other technology will be far more important.