DOHC or SIBC for Corvette C7

[balthazar]

If I were running an Engineering department, that thread Olds referenced would be what I would love to do / any manufacturer SHOULD be doing : direct, apples-2-apples comparisons/analysis to determine what works better. And -of course- there are numerous compromises to satisfy in production.... but still; seems like a LOT of conjecture and generalization, when we 'should' have science on all this.

[CaddyXLR-V]

PUSHROD ENGINES ARE NOT LIMITED TO 2 VALVES PER CYLINDER

can we all agree on that at least?

Here's a quote from dwightlooi on that:

The Duramax head is not particularly good for airflow (the intake and exhaust ports run into one valve first then the other since the valves are tandem not side by side). Also, it is also possible only in a diesel because the Diesel engine uses a a completely flat combustion chamber roof and all four valves are parallel. The approach -- using one rocker to push down on two parallel valves connected by a bridge is not feasible for a gasoline engine.

And another:

The main problem with 3-valve, twin in-block cam designs such as those proposed by GM a few years ago is that the rods themselves compete for space with the intake runners and ports. It is impossible to have straight, unobstructed runners and intake ports. Perhaps the reason these designs did not make it to production is because the intake port issues limits flow improvements to a point where improvements over 2-valve designs become intangible.

Edited November 19, 2009 by CaddyXLR-V

[Drew Dowdell]

Lets also not forget the 2.0 LNF with the GM Performance Turbo Up grade that is California legal with a 5 year 100,000 mile warranty get 145 HP per liter.

Mmmmmmm Regal 2.0t + GM Performance Turbo =

[CaddyXLR-V]

Mmmmmmm Regal 2.0t + GM Performance Turbo =

What would interest me more would be if they hooked 2 of those together, and made a 4L V8 turbo. With the same hp/L it could be making 580hp. Or even a 3.0L I6 with 435hp. They would make some nice engines for a CTS.

[regfootball]

No, I completely understand it. Do you not understand that Ford design is not a very good design, and is big even by DOHC standards? And I have done work, and rebuilt both DOHC, and OHV engines before. So I know their size.

i don't think the hood of a DOHC XLR is much higher than that of the corvette.

and the hood height is somewhat meaningless on the corvette since the fender bulges are the highest part of the corvette's hood.

if anything to shorten the hood on the vette by using an engine and powertrain that is not as long would be good. then maybe the vette could shrink in length, which overall would lessen the structural requirements and weight for the whole damn car. I am sure crush space for one is a lot less with a v6 than a long huge v8.

and hood height again on the ZR1 corvette is a moot issue as well since they had to add the big friggen power bulge for all that external plumbing. i don't see that being a very compact arrangement.

if chevy is gonna stick with pushrods then they need to make a top tech pushrod no bigger than say 4.5-5.0 liters, and they need to keep the stroke short to keep revvability high. if they still have huge bore centers, then the whole thing just becomes a pointless exercise.

people just might have to accept that the next vette due to epa reasons will have a base 3.6 without turbo putting out about 325hp. it makes sense then if they need to engineer the chassis to accept smaller motors at that point the turbo is an easy add for uplevel versions. less time spent mating the block and powertrain to the chassis.

[regfootball]

PUSHROD ENGINES ARE NOT LIMITED TO 2 VALVES PER CYLINDER

can we all agree on that at least?

sure, but the simplicity for pushrod motors falls apart when you add the extra valves.

[regfootball]

Listen up SMK. I am completely, utterly serious about this.

You will be banned from these threads if you continue.

Understand these following statements before you post again.

1. There is no packaging advantage for pushrod inline engines. That is why DOHC is better on a 4 cylinder.

2. There has been an utter lack of development on pushrod V6 engines. The trait of having pushrods is not the cause of their "inferiority"

3. There is a massive packaging advantage that can be had with a pushrod V8. The differences in external dimensions are gigantic.

4. The Corvette, like the CTS-V, can smack around cars twice it's price and do it with a pushrod.

5. The Koenigsegg is over 5 times the price of a ZR-1. I find no trouble jumping to the conclusion that GM would have no problem coaxing 1,000 HP out of the LS series if they could charge even half that.

in this instance all his points are valid and i don't think you can ban someone for simply disagreeing. not allowing other voices here?

[Robert Hall]

I would assume the main reason GM and Chrysler didn't long ago replace their pushrod V8s w/ SOHC/DOHC V8s is the cost and complexity for manufacturing them for trucks, since trucks are the main volume market for these engines?

Chrysler has had an OHC V8 for trucks and Jeeps, but it doesn't seem to have been successful.

[Camino LS6]

I would assume the main reason GM and Chrysler didn't long ago replace their pushrod V8s w/ SOHC/DOHC V8s is the cost and complexity for manufacturing them for trucks, since trucks are the main volume market for these engines?

Chrysler has had an OHC V8 for trucks and Jeeps, but it doesn't seem to have been successful.

Thus it won't happen.

[Drew Dowdell]

in this instance all his points are valid and i don't think you can ban someone for simply disagreeing. not allowing other voices here?

No, his points aren't valid. There are no benefits to having a pushrod 4-cylinder over a OHC 4-cylinder, there are benefits to having a pushrod V8 over an OHC V8. Thus his point, which he repeats often, is invalid.

GM's V6 pushrods aren't inadaquate because they are pushrods, they are inadequate because they've had relatively zero development dollars thrown at them compared to the HF series.

SMK repeatedly fails to understand that a DOHC and a pushrod of equal displacement will not have equal external dimensions. SMK fails to understand that you will not be able to fit a 6.3 litre DOHC V8 into the space that a 6.3 litre pushrod just barely fits in. Yet he continues to state this as true.

The CTS-V and Corvette do use a pushrod to smack around vehicles way out of their price class . This has been very publicly demonstrated.

Bringing the Koenigsegg into the discussion is just trolling. The Koenigsegg is over $500k. GM could outfit a Corvette with a Pratt & Whitney and still have it cost less. If the factory 638hp of the ZR-1 isn't fast enough for you, Lingenfelter will happily sell you an upgrade to about 680hp for roughly $3k.

So no.. it's not just differences of opinion. He's trolling by repeatedly posting information he knows to be false.

Everyone here is entitled to their own opinion.... however you're not entitled to your own facts.

[A Horse With No Name]

Mmmmmmm Regal 2.0t + GM Performance Turbo =

That is utter absolute automotive Lust IMHO.

Wow...that has me thinking "unclean" thoughts about a car...

Chris

[A Horse With No Name]

...and probably profoundly stupid but...

I think that MINI did itself a disservice by bringing out the Clubman, and then planning on bringing out the Crossman crossover, etc.

Think GM would make the same mistake by changing the basic formula of the Corvette. Corvette is old school American Hot Rod with some new school tech thrown in. Change it too much and your diluting the formula.

Chris

[Robert Hall]

Think GM would make the same mistake by changing the basic formula of the Corvette. Corvette is old school American Hot Rod with some new school tech thrown in. Change it too much and your diluting the formula.

Chris

Which is why the mid engined Corvette ideas will never get of the ground..probably as likely as a Corvette based on a shorted Epsy Dos or W-body platform would be.

[hyperv6]

Why do some people not acknowledge others strong points in these discussions? That is the proper way to have a civil discussion.

Everyone has a right their opinion right or wrong. At this point it is best to agree to disagree and just wait to see who is right in the future.

This is an argument no one will win till GM tells us their plans.

Debate is good for all to make their points but to threaten to ban someone just because they are not agreeing and are supporting their positition is wrong. If you don't agree just stop responding after ytou have made your point and everyone is done.

While I do not agree with everything here I respect the others ideas too. At this point I think we all need to be a little more adult here or just let it go.

If no new ground can be covered here it would be best to close the thread for the sake of all. I hate to see that but it may keep things civil. We can revisit this later when we get more info to work with or debate.

[FloydHendershot]

So Ferrari, Porsche, Aston Martin, Jaguar, Maserati, BMW, Mercedes, Koenigsegg, and Audi are using the wrong engine? While the Vette has what the Dodge Ram and Chevy Silverado have. If I am building a sports car, I want what Ferrari has, not what the Dodge Ram has.

There is something special about American muscle that maybe you would be surprised how many people fall in love with it after a spin. Jeremy Clarkson

liked to kid about the donkey cart suspension but now he owns one. And yes, many people like what Ferrari has but ask Johnny o'connel or Jan Magnussen and chances are they will tell you their thoughts.

Listen up SMK. I am completely, utterly serious about this.

You will be banned from these threads if you continue.

Understand these following statements before you post again.

1. There is no packaging advantage for pushrod inline engines. That is why DOHC is better on a 4 cylinder.

2. There has been an utter lack of development on pushrod V6 engines. The trait of having pushrods is not the cause of their "inferiority"

3. There is a massive packaging advantage that can be had with a pushrod V8. The differences in external dimensions are gigantic.

4. The Corvette, like the CTS-V, can smack around cars twice it's price and do it with a pushrod.

5. The Koenigsegg is over 5 times the price of a ZR-1. I find no trouble jumping to the conclusion that GM would have no problem coaxing 1,000 HP out of the LS series if they could charge even half that.

It's frustrating and like the old saying goes it's not the elephants you worry about it is the mosquitoes. At times it feels like you would be better served by talking to a bag of hammers. Just remind SMK that the adults were talking. But really, the ignore button still works no need to be too harsh.

[hyperv6]

Mmmmmmm Regal 2.0t + GM Performance Turbo =

2.0 + GM Performance Turbo upgrade + 6 Speed =

I just spoke to the engineer I know at GMPD. He told me histroy on how they came about doing the kit to upgrade the Turbo. I hope they can come up with a flash for this car as a dealer installed option. The dealers make a killing on these kits + Install cost. GM give you a flash, 2 connectors and two T MAP for $500-$600. They have sold out the kits twice in one year. GM has made a buck on this.

[Intrepidation]

There is something special about American muscle that maybe you would be surprised how many people fall in love with it after a spin. Jeremy Clarkson

liked to kid about the donkey cart suspension but now he owns one. And yes, many people like what Ferrari has but ask Johnny o'connel or Jan Magnussen and chances are they will tell you their thoughts.

Did Clarkson actually buy one? I know he loved it when he drove it in season 12 but I didn't know he actually bought one.

[regfootball]

Everyone has a right their opinion right or wrong. At this point it is best to agree to disagree and just wait to see who is right in the future.

This is an argument no one will win till GM tells us their plans.

Debate is good for all to make their points but to threaten to ban someone just because they are not agreeing and are supporting their positition is wrong. If you don't agree just stop responding after ytou have made your point and everyone is done.

While I do not agree with everything here I respect the others ideas too. At this point I think we all need to be a little more adult here or just let it go.

If no new ground can be covered here it would be best to close the thread for the sake of all. I hate to see that but it may keep things civil. We can revisit this later when we get more info to work with or debate.

[regfootball]

...and probably profoundly stupid but...

I think that MINI did itself a disservice by bringing out the Clubman, and then planning on bringing out the Crossman crossover, etc.

Think GM would make the same mistake by changing the basic formula of the Corvette. Corvette is old school American Hot Rod with some new school tech thrown in. Change it too much and your diluting the formula.

Chris

clubman and other mini variations of the original are results of marketing people grabbing at new straws. can you imagine a 4 seat miata?

Edited November 20, 2009 by regfootball

[regfootball]

Which is why the mid engined Corvette ideas will never get of the ground..probably as likely as a Corvette based on a shorted Epsy Dos or W-body platform would be.

i was looking at some Cien photos earlier today. THAT is the mid engine car GM desperately needs to build. which btw, a cien would need a dohc v8 to be credible.

[Camino LS6]

The Cien would make a huge splash with any powerplant.

Though it deserves something very special.

[Justin Bimmer]

Reg, you are misunderstanding this completely.

What olds was posting was not a position in a disagreement. He was posting information that was factual and was being dispuited.

Think of it like this:

Olds says: "The sky is blue most of the time"

SMK says: "No, the sky is never blue"

That is the problem here.

[Drew Dowdell]

There is something special about American muscle that maybe you would be surprised how many people fall in love with it after a spin. Jeremy Clarkson

liked to kid about the donkey cart suspension but now he owns one. And yes, many people like what Ferrari has but ask Johnny o'connel or Jan Magnussen and chances are they will tell you their thoughts.

It's frustrating and like the old saying goes it's not the elephants you worry about it is the mosquitoes. At times it feels like you would be better served by talking to a bag of hammers. Just remind SMK that the adults were talking. But really, the ignore button still works no need to be too harsh.

As a mod, I can't ignore anyone unfortunately.

[Drew Dowdell]

Everyone has a right their opinion right or wrong. At this point it is best to agree to disagree and just wait to see who is right in the future.

This is an argument no one will win till GM tells us their plans.

Debate is good for all to make their points but to threaten to ban someone just because they are not agreeing and are supporting their positition is wrong. If you don't agree just stop responding after ytou have made your point and everyone is done.

While I do not agree with everything here I respect the others ideas too. At this point I think we all need to be a little more adult here or just let it go.

If no new ground can be covered here it would be best to close the thread for the sake of all. I hate to see that but it may keep things civil. We can revisit this later when we get more info to work with or debate.

SMK is repeatedly posting false statements that aren't opinions despite being politely corrected in the past. He is entitled to his opinions. He is not entitled to his own facts.

Purposely posting false statements repeatedly is trolling.

[Drew Dowdell]

Why is it that the Corvette beating out cars twice it's price doesn't count if it doesn't have DOHC?

[smk4565]

GM's V6 pushrods aren't inadaquate because they are pushrods, they are inadequate because they've had relatively zero development dollars thrown at them compared to the HF series.

SMK repeatedly fails to understand that a DOHC and a pushrod of equal displacement will not have equal external dimensions. SMK fails to understand that you will not be able to fit a 6.3 litre DOHC V8 into the space that a 6.3 litre pushrod just barely fits in. Yet he continues to state this as true.

GM around 2004 had a lot of pushrod V6s (about 75%) and DOHC V6's also. They could have put money into the pushrods, but they didn't, they put the money into the high feature engines. If the pushrod V6 had such potential, they would have invested in it, rather than going to all DOHC on Chevy and Buick sedans/SUVs (save for the Impala, Lucerne, GMT900s). GM chose DOHC V6 over pushrod V6 (just as all the imports, Ford and Chrysler did)

I am aware that a DOHC engine takes up more physical space than a pushrod, but in many cases a 4-4.6 liter DOHC can do what a 6 liter pushrod can do. So they wouldn't need a 6.2 liter DOHC V8, a 4.4 liter could get the job done. Mercedes gets a V12 DOHC under the hood of the SL600, that car is no bigger than a Vette. They could figure a way to get a DOHC V8 under the C7's hood.

The reason GM has the LS engines is because of cost plain and simple. They are cheaper to build than a Northstar (or similar) engine, and it is cheaper to develop the LS series some more than to spend $300 million on a new DOHC V8.

[A Horse With No Name]

clubman and other mini variations of the original are results of marketing people grabbing at new straws. can you imagine a 4 seat miata?

NO!

Chris

[A Horse With No Name]

The reason GM has the LS engines is because of cost plain and simple. They are cheaper to build than a Northstar (or similar) engine, and it is cheaper to develop the LS series some more than to spend $300 million on a new DOHC V8.

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

[A Horse With No Name]

Oh, and to everyone reading this thread:

Take a C5 Z06 or a C6 Z06 and run it at rull throttle and feel the LS motor. I've DONE IT. Once you've DONE IT you won't worry about DOHC etc. The LS is totally kick butt as a mill.

Listening to smk and a few others debate performance mills is about like listening to virgins debate about sex.

GO DRIVE THE DARNED CAR AND REPORT BACK ONCE YOU"VE DRIVEN IT IN ANGER.

Chris

[Camino LS6]

Priceless!

[Drew Dowdell]

GM around 2004 had a lot of pushrod V6s (about 75%) and DOHC V6's also. They could have put money into the pushrods, but they didn't, they put the money into the high feature engines. If the pushrod V6 had such potential, they would have invested in it, rather than going to all DOHC on Chevy and Buick sedans/SUVs (save for the Impala, Lucerne, GMT900s). GM chose DOHC V6 over pushrod V6 (just as all the imports, Ford and Chrysler did)

GM had DOHC V6es in mainstream cars as far back as 1990... ya know, before Toyota and Honda offered them.

Do you not think that GM's decision to move away from pushrods in the V6 stemmed from the near constant harping about the 3800 being a terrible engine <which it's not> in the press?

The automotive press as a whole compares EVERYTHING to the freaking M3 as if it were the only car worthy of existence. Look at all the reviews bashing the Lucerne's "unrefined" powertrain.... my time with the Lucerne was quite satisfying. It did everything I asked it to do, silently, with authority, and returned 31mpg highway. In the driver seat there is no way you could tell if the powertrain was refined or not because you couldn't flipping hear it.

I've also driven an Avalon.... there was nothing remarkable about the engine that would make me pick the Avalon over the Lucerne...... and that was even before we got to anything like looks. The power differences are a non-starter for me because it isn't great enough to matter in this kind of car. I'm not challenging Lutz to a race at Monticello, I'm getting to Columbus at a steady 75mph.

[Chevy Nick]

PUSHROD ENGINES ARE NOT LIMITED TO 2 VALVES PER CYLINDER

can we all agree on that at least?

Agreed, here are some:

http://araoengineering.com/LSX.htm

[balthazar]

>>"i was looking at some Cien photos earlier today. THAT is the mid engine car GM desperately needs to build. which btw, a cien would need a dohc v8 to be credible."<<

I'd like to see a triple-turbo inline 12. Summin' different.

-- -- -- -- --

>>"but to threaten to ban someone just because they are not agreeing and are supporting their positition is wrong."<<

Olds stated his position succinctly and completely. Opinion is one thing, unsupportable blather repeated incessantly is another. Banning is up to mods- I would not suggest such either way- not my place.

[CaddyXLR-V]

Oh, and to everyone reading this thread:

Take a C5 Z06 or a C6 Z06 and run it at rull throttle and feel the LS motor. I've DONE IT. Once you've DONE IT you won't worry about DOHC etc. The LS is totally kick butt as a mill.

Listening to smk and a few others debate performance mills is about like listening to virgins debate about sex.

GO DRIVE THE DARNED CAR AND REPORT BACK ONCE YOU"VE DRIVEN IT IN ANGER.

Chris

Does a GTO with an LS2 count? Because I have driven that car hard, many times. But my opinion stays the same. If they put the same time and effort into a 4-5L DOHC turbo engine as they do the LS engines, they could get more out of it.

[CaddyXLR-V]

GM had DOHC V6es in mainstream cars as far back as 1990... ya know, before Toyota and Honda offered them.

Do you not think that GM's decision to move away from pushrods in the V6 stemmed from the near constant harping about the 3800 being a terrible engine <which it's not> in the press?

The automotive press as a whole compares EVERYTHING to the freaking M3 as if it were the only car worthy of existence. Look at all the reviews bashing the Lucerne's "unrefined" powertrain.... my time with the Lucerne was quite satisfying. It did everything I asked it to do, silently, with authority, and returned 31mpg highway. In the driver seat there is no way you could tell if the powertrain was refined or not because you couldn't flipping hear it.

I've also driven an Avalon.... there was nothing remarkable about the engine that would make me pick the Avalon over the Lucerne...... and that was even before we got to anything like looks. The power differences are a non-starter for me because it isn't great enough to matter in this kind of car. I'm not challenging Lutz to a race at Monticello, I'm getting to Columbus at a steady 75mph.

Oh the 285hp 3.4L DOHC that they abandoned? If they followed through on that engine it would have been much better than the 3.8L.

[Lamar]

A couple of responses to smk4565 and engine head configurations:

Bentley's 6.75L V8TT, the one they put in the Mulsanne, Brooklands, and Azure, is a pushrod design. Their only DOHC mills are in the Continental Flying Spur/GT... and are (I'm pretty sure) Andi engines with extra plumbing.

Mercedes' V12 engines are 3V SOHC, not 4V DOHC.

Just saying...

[regfootball]

the corvette sells to people with money. the appeal of the corvette to that bunch is the attributes of a race / performance car at a price they can justify as a toy.....spare car.

these are the type of people that probably would love to have a ferrari. but like the rest of us ! they need to live frugal and frugal for them is 'chevy'.

i don't think ferrari had any issues packaging a 460+ hp 4.3l v8 in its new California.

the corvette has to emulate those cars in a way to appeal to the folks with money who actually buy the cars. i.e. the folks who spend their time crafting ponzi schemes.

for the record, the 3800 had run its course by about 2000......if not even before. I think if GM saw it fruitful to invest a bunch in an all new pr engine they would have. the 3.9 and 3.5 evolutions were not clean sheet, they were stopgap revisions to keep factories and unions running with little cost. the other thing to keep in mind is GM is more and more global and has to sell engines with displacements that work in other countries where they tax displacement and discourage it. an engine developed by GM has to have the ability to be marketable on many continents. again, the LS may be wonderfully efficient at 75 mph in 6th, but which engine gets the better epa ratings in the test cycle. no one seems to want to acknowledge that this is driving a lot of GM's engine planning. its why your malibus are mostly 2.4 4's instead of the 3.5v6.

interesting anecdote. my aztek is quiet inside. or at least it gives the IMPRESSION of having a smooth motor. its just drowned out with a lot of dampening and sound deadeners, and its programmed to shift before you reach the raspy zone. I drove i think it was an Alero one time with the same 3.4 and it was among the most miserable car tests I ever had.

we can hold up the ZR1 as an amazing specimen of a motor....but remember it has what 6.2 litres of displacement and is force fed. isn't the Z06, like 7 litres? the ZR1 is 100 grand and uses all sorts of titanium and such in the engine selectively to actually be able to get it to make that hp. your rotating mass is getting up there compared to the amount of air they can get in and out of there with only the 2 big stiff valves.

the base corvette can't afford all that exotic stuff like titanium valves etc. so if GM gets to the point where mpg and emissions regs mean they have to consider a new base engine, this means they will either have to downsize the displacement of the pushrod v8 which will result in lower hp, or they stuff in a DOHC v6 they can tune to the same level (i.e. 3.6 on steroids) or perhaps look at contracting out a new v8 OHC design.

GM maxxed out the trickery they could to get the ZR1 engine to the level they could. it required a new supercharger design (the project would have been a failure without that eaton supercharger) and all the exotic material for the valves etc. at some point, developing a new engine they can spread out across many products (i.e. cadillac) begins to look like a more long reaching investment. ZR1 and CTSv command 20-25k premiums over their lesser models. if you think GM's cost of that extra 20-25k that went into the engine was at least 15k or more per unit, and globally they move say, at least 10k of those engines each year....that's a 150 million a year that could go into developing that v8 that could potentially see broader application in a clean sheet v8.

so enjoy that zr1 and ctsv motor while its there because i don't think you will see money going into hopping up the pushrod 8 anymore.

nissan 370 makes 350hp. so something like a 4.8 litre base vette motor with similar v8 architecture could make at least 450-460 hp. conversely the 370z weighs close to the same as the corvette. i am not familiar with the 0-60 of the 370z but i think the mpg on the epa cycle is possibly 2 better or something like that. throw a twin turbo on it and then what does it do.

if GM wants to continue to sell the corvette in this regulatory greenweenie environment you can understand why they might have to look at options in this vein, if they decide they just can't get enough power out of the pushrod and downsizing it or getting the mileage up and leaving the power levels where they are.

[Drew Dowdell]

Oh the 285hp 3.4L DOHC that they abandoned? If they followed through on that engine it would have been much better than the 3.8L.

They didn't abandon it. They detuned it so it wouldn't destroy the transmissions. The 3.4DOHC we got was a detuned version of that motor.

[Chevy Nick]

nissan 370 makes 350hp. so something like a 4.8 litre base vette motor with similar v8 architecture could make at least 450-460 hp. conversely the 370z weighs close to the same as the corvette. i am not familiar with the 0-60 of the 370z but i think the mpg on the epa cycle is possibly 2 better or something like that. throw a twin turbo on it and then what does it do.

370's are pathetically underpowered, I've yet to see a fast one in person. No torque.

Throw a twin turbo on a c5 and you're looking at 700-800 hp.

Edited November 20, 2009 by Chevy Nick

[CaddyXLR-V]

They didn't abandon it. They detuned it so it wouldn't destroy the transmissions. The 3.4DOHC we got was a detuned version of that motor.

Which they cancelled and let the 3.8 live on. I would call that abandoned.

[Drew Dowdell]

Which they cancelled and let the 3.8 live on. I would call that abandoned.

The 3.4 DOHC was replaced by the 3.5 from Oldsmobile.

In fact, since 1990, there was only one year, 1996, where you couldn't get a DOHC V6 from GM.

[CaddyXLR-V]

The 3.4 DOHC was replaced by the 3.5 from Oldsmobile.

In fact, since 1990, there was only one year, 1996, where you couldn't get a DOHC V6 from GM.

Well GM should have focused development on those engines, and cancelled the 3.8, 3.1, 3.4 OHV engines, and never started development of the 3.5, and 3.9.

[FloydHendershot]

Agreed, here are some:

http://araoengineering.com/LSX.htm

Outstanding!

[Drew Dowdell]

I don't know about the 3.5DOHC, but the 3.4DOHC was flippin huge! It took up the so much of the engine bay that the engine had to be disconnected from the dogbone and rotated forward to access the rear spark plugs. This is the same engine bay GM was later able to fit a 5.3 litre pushrod V8 in.

[FloydHendershot]

As a mod, I can't ignore anyone unfortunately.

Crude perhaps but it will work.

[hyperv6]

Why don't we all take a constructive angle at this.

Let take the present LS engine and list the way that GM could meet the goals of the next 15 years.

The goals are.

Better Mileage for future regs.

Retain present power and have the ability to make more power if needed.

Meet toughter EPA regs. Subject to be even tougher in the future.

Improve refinement.

Must work for trucks, Vette and Cadillac.

If there are any other goals feel free to add them.

The key most companies are showing are smaller engines. Can they make a smaller pushrod engine that will meet these goals?

Supercharging is not the prime choice of a power adder with most companies and Turbo's are starting to become the norm on many types and kinds of vehicles.

As witht he ZR-1 I know they can go to around 725 HP with the engine as it is now and still meet present CAFE, Emissions and Warranty. This came from a Guy in powertrain. His numbers they saw reliable on the dyno were even higher than what we got.

GM at this point only has ever built two OHC engines that were really any good and neither have been taken to where they could go. The N star and Eco.

If you want to make the Pushrod live what areas can they improve it. What do you know they can do to make it more efficent in more areas. Right now I am sitting just across from a cust away LS6 and know what the aftermarket has to offer. They all can add a lot of reliable power but few add efficency.

I see a lot of reasons given to say why DOHC will not work or why but few here have given the reasons or ways to improve the present engine. GM can not just sit still on this. If they plan to keep it what will they do to advance it more. How will they do more with less CID?

I know GM is on a crash program to cut weight but that is not going to be enough. So lets keep this to keeping Pushrods alive.

At least I hope this will move things in a positive direction. Lets give it a shot.

Be prepared to back up claims if needed. We all can do that but only so properly not just to snipe. Keep in mind if you can back it up it ai'nt braging.

Lest see the ideas!!

Note don't add Direct Injection as we already have it coming.

Edited November 20, 2009 by hyperv6

[CaddyXLR-V]

I don't know about the 3.5DOHC, but the 3.4DOHC was flippin huge! It took up the so much of the engine bay that the engine had to be disconnected from the dogbone and rotated forward to access the rear spark plugs. This is the same engine bay GM was later able to fit a 5.3 litre pushrod V8 in.

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

They are on top of the heads. Where are they on GM's OHV engines? On the side. Which do you think would be easier to get to?

Heres a picture of a 3.8L

http://forums.justcommodores.com.au/attachments/general/59240d1233910612-history-lesson-3800-v6-owners-3800-series-ii-3.8l-v6-l36-_small.jpg

Edited November 20, 2009 by CaddyXLR-V

[ShadowDog]

... Do you not think that GM's decision to move away from pushrods in the V6 stemmed from the near constant harping about the 3800 being a terrible engine <which it's not> in the press? ...

Which was odd to always read about since it won numerous awards throughout its life-cycle. The L36-L26 (Naturally-aspirated pushrod V6) was bulletproof and the L67-L32 (Supercharged Series II & Series III) was a gem of an engine.

Oh the 285hp 3.4L DOHC that they abandoned? If they followed through on that engine it would have been much better than the 3.8L.

They didn't abandon it. They detuned it so it wouldn't destroy the transmissions. The 3.4DOHC we got was a detuned version of that motor.

So goes the story of the 3.4L DOHC, which, as far as I could ever research was a myth. The actual engine buildup from Fiero tuners revealed that the amount of effort to bring an engine like that to market would be the equivalent of all the moneys that went into the R&D of a Vette engine... never mind that it would be going into a FWD car with an automatic transmission, which seemed extremely pointless. While the Getrag 5-speed manual was optional, it only existed from 1991 to 1993, but offered the ability to build up enough to handle turbo applications that Fiero owners were thrilled with. The test-bed of using F-bodies on the R&D track is what caused so many people to speculate that the LQ1 DOHC was meant to be the replacement for the V8's in the Camaro and Firebird. Again... all speculation.

Which they cancelled and let the 3.8 live on. I would call that abandoned.

No, hardly abandoned. The engine itself was derived from the Quad-Four with great, albeit staggeringly expensive success. The cost of ownership of the LQ1 DOHC was significantly higher than that of the L36 pushrod which replaced it. It was the market that lost faith in the engine since it was such a PITA to work on.

The 3.4 DOHC was replaced by the 3.5 from Oldsmobile.

In fact, since 1990, there was only one year, 1996, where you couldn't get a DOHC V6 from GM.

You could actually get the LQ1 from 1991 through 1997 from the Monte Carlo / Lumina lineup. It was the Cutlass and Grand Prix that did the changeover to the 3800 in 1996. I have no clue why, but speculate that it was to push out the last of the DOHC engines.

Well GM should have focused development on those engines, and cancelled the 3.8, 3.1, 3.4 OHV engines, and never started development of the 3.5, and 3.9.

I don't think GM would have benefited from this since their best engines were OHV designs. The 3.4 DOHC block was entirely similar to that of the 3.1 pushrod. Its only progressive development was going from multi-port fuel injection to sequential. From my notes, in the last months of its life, GM revised the heads and intake manifolds, giving it a larger throttle body and plenum that had slightly shorter intake runners, combustion chamber modification, and bigger exhaust ports. A slightly higher RPM band was also included through revised camshafts and timing. The fact that it was developed off the same 60 degree blocks as the pushrods provided its limitations. It was just too damned big.

I don't know about the 3.5DOHC, but the 3.4DOHC was flippin huge! It took up the so much of the engine bay that the engine had to be disconnected from the dogbone and rotated forward to access the rear spark plugs. This is the same engine bay GM was later able to fit a 5.3 litre pushrod V8 in.

Spark plugs were the least of all worries (though I managed to change mine without tilting the engine forward by having the right self-custom-made tools just for that engine. The alternator, mounted underneath the engine, was not an ideal location due to its proximity to the exhaust manifold (high heat = premature death). I'm not even going to get into the timing belt. Leaking intake manifold gaskets was a notorious problem and was another time-consuming repair. The engine just made grief for the common person's pocketbook and the shade-tree mechanics knuckles.

I still loved it.

Oh yeah, my point in all this... if further development can be made from a DOHC design to evolve and progress more rapidly than a pushrod design, it would be interesting to see; however, if it ain't broke, don't fix it.

[Justin Bimmer]

On a V6 (with 6 spark plugs) It is not the front 3 that are the problem, it's the back 3. There is a reason why 100,000 mile platinum plugs were invented. With DOHC, you have to move the engine to change the plugs.

[CaddyXLR-V]

Which was odd to always read about since it won numerous awards throughout its life-cycle. The L36-L26 (Naturally-aspirated pushrod V6) was bulletproof and the L67-L32 (Supercharged Series II & Series III) was a gem of an engine.

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.