3900 Drawing

[SappySE107]

That was lorenzo that did that. You can make low end on a DOHC, but its stupid to do so without multi stage intakes at the very least, and variable cam timing optimally.

[gpse3400]

Stupid wasn't the word for it.... More like Interestingly Stupid. Since I didn't change it's displacement I doubt I made much more peak torque. What happend was all the power from 4000 shot down to like 1500 rpm. I've never heard the TDC sound so right. Wasn't so mushy and crappy sounding like mine normally was, almost sounded like a DuraTec Ford, very crabby. 5000 rpm was litterally a barrier. That same thing would happen to any motor if you did that. Hell I'd like to think a VINT would be a diesel engine if that was done to it.... But the valves would probably be compromised before that would ever happen.

[Manitcor]

Why pushrod, that's what I don't understand about GM.

Lyle

1 word torque = 245 ft lbs of it at 2800 RPM to be excat. Try to get that out of an overhead cam.

Coupled with VVT and 2 stage intake and now you have a torquey lowend engine that doesnt fall flat on its face in the topend.

Well I do not have dyno sheets to prove it. But Pocket Rocket played around with the cam timing on the 3.4L, and got it to where it had the low end of s small block chevy. But he said it wouldn't rev past 5-5.5k.

This is true, but once again you fighting the nature of the beast, classicly you could only have the best of one thing (topend or lowend) and then average to so-so power through the rest of the powerband. With the addation of tech like multistage intakes and varible valve timing (and hope beyond all hopes one day electronic valve timimg with solenoids) you can have the best of the lows and the highs.

This can elimiate the lowend issues of overhead cam desgins as well as the topend issues pushrods suffer from. However from what Ive seen as far as production cars go even the OHC import engines that sport VVT still do not produce as much grunt in the lower RPM range that a pushrod can. Not that ive looked extensively but i have a bit and I think you would be hard pressed to find a production overhead cam engine with VVT that can produce 245 ft-lbs of torque at a mere 2800rpm.

I think the idea here was to go with a proven desgin for making torque (something GM does well) and use the technology to make up the top end as opposed to the other way around.

If your looking for your GM DOHC high tech equilvlant its already here in the form of the new Gv6 platform.

[SappySE107]

You are also comparing low displacement to larger displacement. Look at the SHO 3.0 and 3.2. It has low end and top end. You can't make low end torque on an NA 2.0 without some sort of miracle.

[PlatinumZ34]

I have a better idea. Lets mount two inline 6 engines in a V. We all know that an inline 6 will produce 1/4 the hp but 1.5-2x the torque of the average V8. With this crazy garfunkled engine, you'd have 1/2 the horsepower of your average V8 (we'll take the corvette... yes average :P) so around 400, half of that 200hp, and i dont know... 800 torque? There, its the best of both worlds. Thankyou very much. Yes it took me a few years to pass math class.

Seriously though, its just a hell of a lot cheaper to make a pushrod engine with 1 cam, than a Twin DOHC engine with 4 cams and 24 valves and an assload of other problems . Pushrods are probably more of a selling feature to your grandpa and grandma, mom and dad, who dont want some crazy complex twin dohc garbage, they want their simple pushrods that take 20 minutes to completely strip down. (im speaking from a grandparents view who hasn't owned a GM newer than 1991.. the rest of us know..)

One thing i notice in the drawing... Yay I dont have to pull my transmission/drop the engine to change my alternator!!!

[TheProfessor]

i spy like 8 pullys

[PlatinumZ34]

i see 2 pistons... WTF! but no, i'd rather having to struggle with a belt then have to pay for a realignment after alternator change... time is not money, money is money. I have time to kill...

[TheProfessor]

well at least it has a timing chain and not a belt

[PlatinumZ34]

ahh so it does, yes thats a plus. At least it doesn't have a timing chain AND a timing belt... like some other GM engines.. ..

[TheProfessor]

dude what engines have both???

[PlatinumZ34]

the LQ1... From what i understand (i havne't taken this thing apart yet...)

But supposedly a chain from the crank drives the pulley that drives the timing belt. I dont know, LQ1 has so much misinformation its sick. And my haines manual is like... timing belt: See radiator cap. Cause i think the guys that wrote it were intoxicated at the time.

I can't remember what it was, but something about a timing chain... oh well nm, just ignore what i said.

[TheProfessor]

no way for real
i thought it just had a belt

[PlatinumZ34]

Ill read through my haines, but im pretty sure theres just a belt... I dont know, im sure theres a few people on this board... as in... tonnes, who could tell me im an idiot... about this i mean.

[geoffinbc]

The 3.4L DOHC has both.

This anti pushrod complex that some people have really confuses me. Why is a pushrod motor bad if it is smaller, lighter, cheeper and has less moving parts yet makes more power, fewer emissions, has longer life and more reliable operation than a DOHC equivalent? Go take a look at the Chevrolet LS2 smallblock and then think about it. Then when the LS7 comes rolling around you will need to shut the hell up about your DOHC infactuation

[Anonymous]

It isn't anti pushrod, its pro DOHC. Drive one and you'll know why.

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.

And I'm anti less than 4 valves per head, not pushrods.

How do you think more power? GM has NEVER made a 60*V6 that made more power than the LQ1 up until now. And I think we all know that the LQ1 has much more potential. I shouldn't even have to debate that.

I passed emissions, with headers, no AIR system, and no EGR.


You should really take a look at the 4 valve SBC heads, and why they are gaining about 120 wheel hp on an LT1 with simply bolt on heads.