3900 Drawing

[bszopi]

NASCAR pushrod engines with only 2-valves/cylinder are pushing 9400rpm with no problems... hehehe.

[JohnyG]

NASCAR pushrod engines with only 2-valves/cylinder are pushing 9400rpm with no problems... hehehe.

Whats your point? F1 engines sing all the way upto 18k.
Im not too familiar with NASCAR, but im sure their engines dont last much longer than the ones in F1 cars.

-John

[geoffinbc]

More valves do not always make more power. That is dependant on much more than valve count. The LT5 was indeed made to get the power but they did it as more of an experiment. During that time they were trying DOHC motor in all forms. Plus I agree the LT5 was a freakin beast and I love the engine for what it was and could do. But the excess cost and poor reliability ended all DOHC engines that were out during the time.

I have driven several DOHC motors including the new 3.6L and some Honda breeds. So I know whats good and bad about both types of engines. But fact is right now the LS2 and soon to be LS7 is making killer power on what most people would call "old" technology when it really isn't. The design of modern pushrod valvetrains is very high tech.

I dont hate DOHC motors. I know they make killer power. So can pushrods. Dont ever dismiss a pushrod because it has 2 valves. Thats just dumb thinking. It has alot of promising features that make it a great and sometimes better motor.

It is the same thing when people put down an automatic and call it a "slush box" Well alot has changed over time and an automatic tranny will woop the piss out of even the best gear slamer any day. But again I drive a standard and prefer driving a standard because there are alot of features I prefer about a standard. Plus you have added user control and flexability that you do not get from an auto.

But I know where things stand in their own respect so I do not dismiss it because its not faster this or roller that or whatever. So quit being an engine racist and respect things for what they are.

[geoffinbc]

NASCAR pushrod engines with only 2-valves/cylinder are pushing 9400rpm with no problems... hehehe.

Whats your point? F1 engines sing all the way upto 18k.
Im not too familiar with NASCAR, but im sure their engines dont last much longer than the ones in F1 cars.

-John

Actually Nascar motors last much longer. Sometimes 5 hours. Not including the 2 days before that. Oh and an F1 engine displaces a measley 3 litres divided amongst 10 cylinders. Nascar divides 8+ litres into 8 cylinders. So making a 1 litre cylinder turn up to 10 grand is much more impressive. But then on the Formula 1 hand when you get into the 10 grand + range valve train starts to become a challenge. Springs dont work that high so that is why they rely on a pneumatic valve system. Which is really innovative.

[Anonymous]

A 4-valve enigne will always be superior to a 2-valve engine when both are the same. Take 2 small block chevys, same cams, same pushrods, same intake, same everything. Except one has the ****** engineering cyl head, the other has ANY 2 valve. The 4-valve will make more power, a lot more.

You are right about the LT5, and between it and the LQ1, GM wanted little to do with the DOHC motor, and for good reason. For what people wanted, it was a bad choice. It doesn't have great low end, it was expensive to manufactor, etc. The 60*V6 pushrod is a better choice. But not for racing. But GM doesn't care about building race motors for the street.

And as far as autos go, you are right and wrong. There is a point where a well built auto with the right parts will out perform a stick at the track, assuming the stickshift has 1 more gear, and that both are still streetable(highway gears). The point is somewhere like 600hp. Below that, the stick will be faster. The only reason being you have less RPM drop into the next gear. Take the DOHC for example, the autos drop to like 4200 after their shifts, my 5-speed drops to 5k. That 800rpm is a HUGE difference int he LQ1. But above 600hp, an auto can be made to own a stick all around.

[SappySE107]

why is this pushrod vs dohc? Its retarded, this is about the 3900, not the 3.4 DOHC, 2.8 DOHC or 3.6 DOHC. As it sits, the 3900 has more potential than the 3.4 DOHC, unless you are aaron and think 6 TBs makes up for variable cam timing and a 2 stage intake. Dump enough money into any motor and you can get some impressive numbers from it. GM has finally dumped their own money into the 60V6 line and its showing. I like all the 60V6 engines, just the LQ1 is my toy at the moment. If I had a smaller car, id be all over the 3400, 3500, or 3900 (though working on the new pushrods is gonna be much more involved with all that technology sitting on it).

[SappySE107]

Oh, and the LQ1 does have a timing chain, to drive the oil pump "cam" and the belt drive gear. Its on a tensioner and really isn't an issue for the motor unless it has a ton of miles or is severely abused.

[RacerX11]

Nascar divides 8+ litres into 8 cylinders.

Yeah....right. Try 5.87 Liters (358 cubic inches).

Marty

[geoffinbc]

LOL Woops that was a brain fart right there ...

[v6h.o.]

They aren't bad perse, they just could be better. All this talk about your SBC. Remember the LT5? Maybe you should. In the late 80s, early 90s, GM could not get a pushrod SBC to get the power they wanted, while still being streetable and getting the gas mileage they wanted. So they went DOHC. Things have obviously changed..

Hmm... lets take a step back here the LT5 how much HP did it make? oh around 400ish right??? and how much did it cost? for an LT5 vette? an extra how many thousands and thousands of dollars more! also how much room did it take up??

hmm... take a look at the LS6... 405 HP from only one cam and 2 valves and how much extra ? hardly a drop in the hat compared to the LT5.

nothing against the LT5 or DOHC. i like both. but Aaron think before you speak...

[geoffinbc]

why is this pushrod vs dohc? Its retarded, this is about the 3900, not the 3.4 DOHC, 2.8 DOHC or 3.6 DOHC. As it sits, the 3900 has more potential than the 3.4 DOHC, unless you are aaron and think 6 TBs makes up for variable cam timing and a 2 stage intake. Dump enough money into any motor and you can get some impressive numbers from it. GM has finally dumped their own money into the 60V6 line and its showing. I like all the 60V6 engines, just the LQ1 is my toy at the moment. If I had a smaller car, id be all over the 3400, 3500, or 3900 (though working on the new pushrods is gonna be much more involved with all that technology sitting on it).

Yea sorry about the off topic thing. I wonder though. Could old conventional parts be put into a 3900 so that the block can be swapped in place of a tired Gen I or II motor to gain the huge displacement increase and the advantage of the head and block updates? Also what about RWD apps. Because as it stands right now I am looking for a Gen III or IV smallblock to go in my truck. But if the 3900 could work it would be much easier to do and give the truck what I want.

[geoffinbc]

A 4-valve enigne will always be superior to a 2-valve engine when both are the same. Take 2 small block chevys, same cams, same pushrods, same intake, same everything. Except one has the ****** engineering cyl head, the other has ANY 2 valve. The 4-valve will make more power, a lot more.

You are right about the LT5, and between it and the LQ1, GM wanted little to do with the DOHC motor, and for good reason. For what people wanted, it was a bad choice. It doesn't have great low end, it was expensive to manufactor, etc. The 60*V6 pushrod is a better choice. But not for racing. But GM doesn't care about building race motors for the street.

And as far as autos go, you are right and wrong. There is a point where a well built auto with the right parts will out perform a stick at the track, assuming the stickshift has 1 more gear, and that both are still streetable(highway gears). The point is somewhere like 600hp. Below that, the stick will be faster. The only reason being you have less RPM drop into the next gear. Take the DOHC for example, the autos drop to like 4200 after their shifts, my 5-speed drops to 5k. That 800rpm is a HUGE difference int he LQ1. But above 600hp, an auto can be made to own a stick all around.

Where do you get these engine "rules" from. They sound alot more like bad myths to me. Why the hell would a stick out perform an auto if it is below 600HP that is the stupidest shit I have ever herd. They can both be built either way. If you had a 2004R tranny you would have gear ratio so close together they are often better than a 4 speed standard and damn close to a 5 speed. Or Take you pick from one of GM's 5 speed auto out.

Like I said alot has changed. So lets all try to keep up. We dont need any straglers

[PlatinumZ34]

Comparing NASCAR engines to Formula engines is like comparing planes to helicopters.

1: DOHC's are much more expensive
2: With the addition of new technology DOHC isn't required to make more power
3: Would DOHC make more power then SOHC or pushrods? definately more than SOHC, and more topend then pushrod (all things equal)
4: Nothing will beat the low end grunt of a pushrod engine, however DOHC will take a pushrod in the upper RPM's... which is why my car will beat a 1995 Trans Am Formula (5.7 6 speed) after 190km/h. Fuel delivery isn't nearly as good, there is 1 intake valve open for about .000001 seconds that has to let enough gas in to continue acceleration. Thats changed with dual stage intakes and VVT.

Now that we have that settled , back to the 3900. If the engine is making power using the best possible technology available, how do you intend on modding this engine to make more power???

[TheProfessor]

the main thing about DOHC and pushrods is where in the rpm band they make their torque
the dohc motors make theirs at a higher rpm which is the reason that they make more hp but yeah the dohc motors do take up more space, are more expensive, etc...etc
the LT5 was kinda cool though lol

[Anonymous]

Hmm... lets take a step back here the LT5 how much HP did it make? oh around 400ish right??? and how much did it cost? for an LT5 vette? an extra how many thousands and thousands of dollars more! also how much room did it take up??

hmm... take a look at the LS6... 405 HP from only one cam and 2 valves and how much extra ? hardly a drop in the hat compared to the LT5.

nothing against the LT5 or DOHC. i like both. but Aaron think before you speak...

In the later years of the LT5, it made 405. Like from 1993-1995. Read my post, I said IN THAT TIME PERIOD they didn't have the technology to get that power, with the streetability and gas mileage, from a pushrod design. So they went DOHC. Now they haev the technology to make a 400-500hp pushrod, so they do. And for damn good reason. Cost, the ZR1 was right at $60,000.

betterthanyou, it can be assumed that a 600hp car has 600 ft lbs(for comparison). sO YOU TKAE A 200HP Lumina, and my 5-speed will outperform it at the track no matter what you do to the auto. Even with a 4500 tq converter, their shifts still drop them RPM. Mine drops less, which is better. Now if they both had 600hp, the auto, is goign to have a better launch, better traction, and faster shifts. And even though it still drops less in the RPM, it makes it up so fast with 600ft lbs on tap that it sitll gets to the point my 5-speed would be at faster.

But I'll stop now since I did kinda ruin this post....