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[Press] GM Smallblock Gets Three-Valve Head

Rob

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Very interesting. Check this out:

General Motors has proved the value of modern overhead valve (OHV) engine design with its Generation III small-block V8 engines, and the forthcoming Generation IV engines will continue to advance the architecture once considered obsolete. But GM Powertrain recognized the inherent handicaps of a two-valve per cylinder head design that is typical in OHV engines. To further extend the life of the Generation IV V8 and its revised High Value V6 engines, the company has devised a three-valve head design to work with these pushrod engines.

Adding a second intake valve improves intake air flow, which provides some value, but perhaps more importantly the design relocates the exhaust valve and the spark plug within the combustion chamber. The exhaust valve moves from alongside the intake valve to the other side of the cylinder, so less exhaust heat transers to the intake port. The resulting cooler intake charge boosts power and efficiency.

Positioning intake and exhaust valves on opposite sides of the combustion chamber leaves space in the center for the spark plug, which improves combustion efficiency. Together, these improvements boost power output by 10-15% according to the company.

The three-valve engine has the intake valves in a straight line, operating them with a forked rocker arm off a conventional rocker shaft. Because the exhaust valve is on the other side of the spark plug and is not mounted in the same plane as the intakes, some ingenuity was needed to enable the engine to operate that valve using the same block-mounted camshaft arrangement used in two-valve engines.

The solution is a pair of rocker arms. One mounts on the rocker shaft where the exhaust rocker arm would be on a two-valve engine. Instead of acting on the valve, however, the first rocker pushes on a short, nearly horizontal pushrod that runs across the head to a freestanding stud-mounted rocker arm.

The second rocker arm pivots the movement into the right direction for the exhaust valve.

The three-valve heads are about 1 in (25mm) wider than the two-valve heads, but they maintain the low profile that is an advantage of OHV engines. The new heads will work with the displacement-on-demand (DOD) cylinder-deactivation system that will arrive on the two valve Generation IV engine and High Value V6 for better fuel economy.

"The three-valve design adds complexity but uses the type of components with which GM is very familiar, so reliability shouldn't be a problem," said Frederick Rozario, Development Engineer, Advanced Powertrain at GM. "And while the added mass in the valvetrain might seem to be an obstacle to high rpm operation, the Corvette engine will rev to 7000 rpm with a 30% margin of safety. It can go to 8000 rpm safely," he added. A special jig will hold the parts together so the whole valve actuation assembly can be installed as a unit on the head.

"A weakness of single camshaft engines is the inability to separate intake-cam timing from exhaust-cam timing for maximum efficiency and minimal emissions. But a cam phaser that adjusts the advance or retard of even a single cam, depending on conditions, is still vey valuable," Rozario said. "The cam phaser on this engine provides 80% of the benefit of a system with separate intake and exhaust phasers.

The phaser mounts under the water pump in the traditional timing chain location, so it does not require any additional space underhood. The water pump is new too, because the higher-output engine increases the demand for cooling. The 6.3-L version of the engine will produce 500 hp (373 kW), for example. So the new pump produces twice the 80 gal/min (300 L/min) of coolant provided by the two-valve engine's water pump.

The DOD system and cam phaser increase the demand for oil pressure, so both the V8 and V6 engines get improved oil pumps. The V8's is a two-phase oil pump, switching between high and low flow as needed to maintain the necessary oil pressure without suffering excessive parasitic losses when lower pressure is sufficient. The V6 is even more efficient, with a variable displacement oil pump that continuously adjusts its output for maximum efficiency.

The engines also feature optimized exhaust manifolds with equal flow runners for each cylinder.

Dan Carney

Source: SAE Tech Briefs - 9/2003
http://www.sae.org/automag/techbriefs/09-2003/1-111-9-26.pdf
 
Very interesting, but boy oh boy is it ever getting more complex :eek

tom...
 
Rob said:
Very interesting. Check this out:

Positioning intake and exhaust valves on opposite sides of the combustion chamber leaves space in the center for the spark plug, which improves combustion efficiency. Together, these improvements boost power output by 10-15% according to the company.

The new heads will work with the displacement-on-demand (DOD) cylinder-deactivation system that will arrive on the two valve Generation IV engine and High Value V6 for better fuel economy.

The DOD system and cam phaser increase the demand for oil pressure, so both the V8 and V6 engines get improved oil pumps.

Dan Carney

Source: SAE Tech Briefs - 9/2003


So we the Gen IV is a 3 valve Hemi, right?

Ah, we are getting DOD after all! Rob, do you think the 3 valve tech is accross the board for vette? ... will the base vette get 3 valves, or will we only see it in the Z06, as the base vette and trucks remain 2 valve?
 
I suppose we have to take them at their word, but it seems contradictory to increase the amount of moving parts and "connections" between the camshaft and the valve, while increasing the "redline" RPMs. I recognize that technology, build quality, and quality control are all improving, but it sure sounds like something would give @ 8,000 RPM with 2 pushrods and 2 rocker arms and a lifter between the camshaft and the exhaust valve.
 
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Re: Re: [Press] GM Smallblock Gets Three-Valve Head

LongTimer said:
Rob, do you think the 3 valve tech is accross the board for vette? ... will the base vette get 3 valves, or will we only see it in the Z06, as the base vette and trucks remain 2 valve?

I don't know.
 
Someone said that Hill has said that the Z06 would be more differentiated in the C6 version than in the C5. Perhaps the additional VALVE is part of the uniqueness of the new Z06.

2 valve Gen IV = Base Vette @ 410 - 450 HP?
3 valve Gen IV = Z06 Vette @ 500 - 550 HP?
 
Allright thats IT!!! I am selling the kid, house and current cars so I can get a new ZO6 when It comes out!!!!!
 
UB2 SLOW said:
Allright thats IT!!! I am selling the kid, house and current cars so I can get a new ZO6 when It comes out!!!!!
AHHH... I'll just put the top down on 2002 Convert and drive around the same as I would with more horses at the top end that I would hardly ever use!!!:D
 
Why don't they just admit they are cutting corners and glossing over the fact they are using an old tech engine design. The sooner they adopt the NorthStar system division wide the better.
How many push rod V8s and V6s do Toyota and Nissan have??
 
CFour said:
Why don't they just admit they are cutting corners and glossing over the fact they are using an old tech engine design. The sooner they adopt the NorthStar system division wide the better.
How many push rod V8s and V6s do Toyota and Nissan have??
And when will you admit the fact that you dislike GM and dislike the Corvette and you complain more about the car and GM than an old man who has run out of his supply of Metamucil. Give it a rest Ross.
 
Even you know Rob that GM is all over these Forums. As long as they think the car buying public accepts there sub standard products they will continue to make the same old crap. Face it by now GMs High Tech car the "Corvette" should have at LEAST a DOHC engine like the ZR1 had YEARS ago. For the money they want for this car today it should have 21st century engineering. A push rod car is not state of the art by any means no matter how pretty the body. The Corvette at around 50K is NOT CHEAP any more when compared to the Nissan Z car. Its time GM bellied up to the bar and give us a truly modern Corvette for the price they are asking.
 
CFour said:
Even you know Rob that GM is all over these Forums. As long as they think the car buying public accepts there sub standard products they will continue to make the same old crap. Face it by now GMs High Tech car the "Corvette" should have at LEAST a DOHC engine like the ZR1 had YEARS ago. For the money they want for this car today it should have 21st century engineering. A push rod car is not state of the art by any means no matter how pretty the body. The Corvette at around 50K is NOT CHEAP any more when compared to the Nissan Z car. Its time GM bellied up to the bar and give us a truly modern Corvette for the price they are asking.
Sorry, but I disagree with you. I may be a ZR-1 owner and I love my Vette, the LT5 engine and the heritage that comes with the car, but I don't think that another DOHC engine is a prudent direction to go in and you know damn well that it isn't either.

The small block V-8 as we know it is damn good at what it does. The perfect example of this is the LS6 engine. It produces the same amount of horsepower as a second generation LT5 engine does with a hell of a lot less parts and weight, and it's my own personal opinion that there is even more horsepower in that outdated technology that has yet to be tapped.

Again, I love my Vette, I love ZR-1s and LT5s but in terms of efficiency, I don't think another DOHC architecture is the way to go. Instead of *****ing about GM and their techology, why don't you just sit there quietly like the rest of us and wait to see what comes out of all that old, dusty technology.

As for GM being all over these forums, no I don't necessarily know that and regardless, that has absolutely nothing to do with this discussion.
 
If you like the sound of a sewing machine Rob. Thats a fair assessment of the two motors in my opnion. Just take a good listen to a pushrod motor compared to your Mercury built work of art.
 
CFour said:
If you like the sound of a sewing machine Rob. Thats a fair assessment of the two motors in my opnion. Just take a good listen to a pushrod motor compared to your Mercury built work of art.
Ross, sound is not based on engine architecture alone.

A stock late model Trans Am or Camaro or even a standard V-8 powered Mustang GT off the factory line sounds pretty damn stout and in my opinon, a hell of a lot better than a stock Corvette off the factory floor. And, the higher end F-bodies share the same powertrains as standard Corvettes, with the exception of some mild detuning. Otherwise, the general engine architecture over both platforms is nearly identical.

In my opinion, yes, today's Corvette, to me sounds too tame as compared to a ZR-1, but sound is not based upon engine architecture alone.
 
only have one chance to make a first impression...will try to be concise! (besides posting wirelessly from pocket pc!)

Background...come from a family with 250+ years of combined gm experience from factory workers to execs.

Due to disdain of big stuffy bureaucracy never wanted to work there 'cept as a test driver! First vette drove was one of the first z-r1's red! Made quite an impression and quite a step up from a pontiac j-2000 (later known as sunbird).

Finally lets just say one of my relatives had a hand in the Pontiac Fiero so if You liked it You might want to listen Ross.

My opinion...have been lurking for years this last negative Ross post got me to finally reply. I agree with Rob 99% and Ross only 1%. Gm makes/made some pretty crappy products (see j2000/chevette) but NOT CORVETTE!!! I have NO inside knowledge of the c6 but I know these 3 positive things

1. it took gm years to dev. magno ride and no one else has it.

2. I am no mechanical engineer but I've read 3 valves are actually even better than 4 (think some fancy bmw's have 3 valves)

3. Read the article more closely...THIS IS A DIRECT INJECTION MOTOR USING ORBITAL CORP'S TECHNOLOGY THAT I READ ABOUT 10+ years ago in auto trade papers. That doesnt mean its a pos but that it took 10+ years to get emissions and costs down.

ps right now I am back in college but if I had the means I'd get an 05 - 06 vette! As it stands its a Saturn which is good for a gm and good for a small car in general (no pun intended).

ps2 would love to debate all night with Ross but Im taking 25+ credit hours need some sleep tonite!!!
 
All Opinions are good ones. Glad I finally got you to post your feelings. I must admit sometimes I "over stimulte" not to be negitive like some think here, but to make people here think "out of the box" about Corvette. Good Comments. :cool
 
Very nice thread!!!

Every one pointing out their best, (and me learnig) I love Vettes and I'm not complaining the way their engines are (pushrods). But GM sooner or later (the sooner the better) will have to get into the 21th Century making a DOHC Vette like the LT5.

:upthumbs
 
People are constantly comparing the LT5 to the LS6 lately in these DOHC vs. pushrod debates.

The common comment is "The LS6 produces the same horsepower as the LT5 with a far more simple design for much cheaper!!!"

Well, I have to say that is not a fair comparison......at all. These engines are TEN YEARS apart, and they put out identical horsepower! Give the LT5 TEN YEARS of developement, and then lets see what kind of output it has! In that respect, I don't find the LS6 very impressive. In fact, a common comment that you hear is "Now if only we could get the LT5 in the Z06's body........" In the last 10 years, Corvette has not gained much ground, and arguably NONE.... Although, admittedly, the ZR-1 did set the bar pretty darn high.

Yes, the transition to DOHC will be costly--but any change is going to be at first. Once it becomes the norm, it's not going to be so "expensive". I don't think technology should stop just because Corvette guys are obviously more familiar with and only know how to fix their pushrod engines. If Corvette is going to evolve and compete on a global market, we need to be a bit broader minded and let go of some history and our childhood biases.......let history be exactly that---history. Pushrod engines are not Corvette's tradition. Corvette's tradition is CUTTING EDGE TECHNOLOGY.

I think this 3 valve design is a step in the right direction.



Brett
 
Out of the box vs out of your mind

Thinking out of the box, dump the Northstar (like the Olds engine), keep the push rod. I will never own another Northstar, wimpiest engine I ever owned and I had a Chevette in '78 and a Corvair in '65. Both were better cars than my Seville, my Eldorado was a good car but gutless.

While were at it lets dump Lutz and get a real car man in there.
 

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