Its already been proven you dont need mega-stroke to make good power on boost, but what kinds of effects would a bigger bore yet smaller stroke have on a turbo/blower car? Most likely to be used on a 6 speed car I would assume?

I dont have any plans for that or anything, just curious about having a boosted setup making power to reaaaaly high R's.

<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

I'm a big fan of short stroke motors in general, so this idea appeals to me; however, even with stock bore/stroke, some folks are approaching 7000 RPM. Adding a bigger (say, 4.1") bore and shortening the stroke (3.2677" stroke 4.8L crank) would allow the motor to be REALLY wound out, but in order to make power that high, you'd have to run one hell of a cam. Other possible issues at that kind of RPM would be injectors (they can only open/close so fast; I don't know if this would be an issue, but its worth considering), ignition system, and most importantly, oil pump.

A short stroke/high RPM motor like that would be great for something like a road race car, where you could pretty much always keep the motor in its power band, but (despite my love for big bore/short stroke motors) for a street car/drag car an all-bore 382 would be the way to go, IMO.

It'd be damn neat to have a short stroke 345 LS1, though... <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

I'm not sure a stock pcm will operate, I mean make changes above 7000 rpms... So the problem is that your AF and fuel trims will go static at 7000...

FWIW I don't think that stock stroke all bores make too much torque so I think the stock 3.622 stroke works pretty good but the Westech/GM 302ci showcar uses that crankshaft.

 

I like the idea of a short stroke big bore for a turbo motor <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> That is what I am working with right now for me upcoming motor. Now mine is not a ls1 but still a motor is a motor to me. My thoughts from going through all of this so far...

I was going into this build with a 434ci stroker but got to talking to some racers that I like there sence and reasons behind it all.
First they said any cube motor will make the power to go insane fast with look at the mustangs most said. In 2000 there was guys running deep into the 7's with 306, 331, 347's.

Now my plans after talking with these guys were to cut my stroke by alot and go with a 3.50 stroke, 4.125 bore setup. The motor will make awesome power and you have the turbos to generate insane tq. The reason most of them steered me away from the big stroke was generating way too much tq for the combo (stock suspension, small tires) Now you can use about the biggest heads you want and stick the cubes rather small and cram tons of air into the cylinders and use your turbo to generate your power rather than wanting the motor itself to be the major piece (sounded funny at first but after getting to thinking about it, It really makes sence)

Would make a nice nice combo for a big bore short stroke though for a car especially with a manual <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> .
Steven <img border="0" alt="[driving]" title="" src="graemlins/gr_driving3.gif" />

 

With all the talk about re-sleeving, its not that bad of an idea.

I would guess this isnt the ideal setup for drag racing which most people care about here (hence the lack of interest in this post). Yea the more rpm's the more engine wear on everything, but its a neat idea to think about. What kind of top-end highway warrior would this make? Not the tremendous low end torque of the superstrokers but on a street tire that torque is usless anyways. You could also gear the **** out of it like the 32v cobras.

I dont think anyone will try this combo anytime soon because of the wear factor involved with these high dollar LS1 parts, but geez this could be a real supra-killa!

<img border="0" alt="[driving]" title="" src="graemlins/gr_driving3.gif" />

 

Big Bore / Short Stroke motors have their pluses and minuses. More stroke means more torque. Your HP is also made at a lower RPM which is easier on parts to an extent.

But, a big bore short stroke motor does have some advantages. You can run an unshrouded Stage III with very good flow numbers, and they will work.

Under a boosted application (like a turbo), a motor that makes RPM will keep cylinder pressure down, and keep from lifting ring lands. The 1200HP twin turbo c4 Corvette has a small roller and a GM Rocket block. It is a big bore/ Short Stroke motor that can turn almost 8000 rpm. It was done this way for just that reason.

But, as stated, there are PCM limitations you have to be aware of.