cndctrdj

alot of you guys get bigger and badder engines for your cars. what about going down to a 327 or a 302? i was talking to a few people about this. smaller engines can spin faster. or so ive been told. i dont know what a stock lt1 will go to without problems but what about going smaller and spinning faster. you could put 4.11's in your car and have an engine that spins to 8k and not lose top speed and totally gain acceleration. its just a thought. i don't even think they offer anything like this but. just something to think about. any input on this would be appreciated.

Josh-'04 GTO

The key to making a car fast is to maximize the power in the rpm range where the car spends most of its time during a run. Think about this for a second. Even if you have a car that can turn 8k rpms, a 3500 lb chassis in a typical street/track combo car would not be that impressive, since this car would probably spend a majority of its time in the 3500-4500 band during a typical street "encounter". A peaky 8k motored car will not be as fast a bigger motored car tuned to run in the required rpm band. Torque is what motivates a car, and horsepower is merely torque over time. There is no way to gain torque faster or easier than additional cubic inches.

Larnach

Wheel thrust is what matters, that is why they use gearing. A car that turns 8000rpm vs. a car that turns 6000rpm has the ability to be geared 133% more than the car turning 6000rpm.

Say the 6000rpm car turns out 400ft. lbs, the 8000rpm car only 330ft. lbs... with proper gearing it can put out the equivelent of 438ft. lbs when geared. That's why more rpm potential = faster acceleration when geared properly, its all about wheel thrust.

rskrause

There is no good reason to destroke a motor for a street or street/strip car. If you are trying to meet a displacement limit then choosing a smaller stroke may be of great benefit, but otherwise, forget it.

Rich Krause

Josh-'04 GTO

Wheel thrust is mostly dependent on engine output!!! Your example is nice, but remember that the original engine output was still 75.34% of the equation. That is why you build an engine that will have maximum output in the anticipated rpm band for the application. An smaller cubed engine that turns 8k will be very peaky, and will require very steep gears, probably 4.56 or 5.12s to get good times out of it. Ever run 4.56s or 5.12s on the street? Didn't think so. Not to mention the fact that you would need a very big stall convertor if you have an automatic. Not even worth considering. Not to mention the nightmare of trying to hook up with steep gears. Which is why my 377 that "only" spins 6000 rpms pounds down ricers that turn 8K plus without breaking a sweat.

unvc92camarors

i've been thinking about this too if i got an lt1
you could throw the 4:10's or even numerically higher gears in there, destroke to 302 (or 327), then throw in that new twin turbo kit from greddy i believe it is, then of course, heads, a cam that keeps that high powerband, etc.
a little bit of money, especialyl for the tt's but..
overall, you would stay more in the powerband with the gears and cam, and as long as its got a free flowing exhaust...it wouldnt be too bad
then with your tranny, if auto, go with a freakign high stall with different shift poitns (of course), or a manual you could use to drop the clutch at 3k or so and you could wind the rpm's as high as you want
just a thought

o, thought of this too, if you got that tt kit, you'd probably want to lower the compression down, so as to use those tt's effectively

Larnach

Your exactly right, its more of an advantage in racing, its back *** backwards for a street car.

Ai

Not even looking at the cost of aftermarket engine management, when you start getting into components that will handle thousands of miles in a 8k rpm engine, you're looking at what's a pretty huge increase in price for most people .

Camaro_Maniac63

Destroking to me would be just a huge waste of money. Torque is king, it is what gets you going.... For the money to build a destroked motor with the components necessary to function properly at 8000rpm continuously, you could just easily build a 350ci engine that will spin to 8000rpm. Then you would have the best of both worlds...

Ai

HP is what you want, because torque is a force, and HP is the capacity to do work. So if you want to accelerate a mass, you want Power. Of course you have to make compromises for something that has more than one purpose like a street car, but if all you want to do is go fast, RPM is your buddy .


There was actually a long thread in Advanced Tech a few mos. ago where Chris B had a difficult time explaining that, even when he mathematically laid it out. If you're curious though, it'd probably be a decent read .

Camaro_Maniac63

Interesting, time to read some more I guess. Thanks, Phil. But still, would a 302 spinning to 8000rpm have an advantage over a 350 that spins to, say, 7000rpm? I would think not. Let me go read that post now...

Ai

Oh I was just throwing something out there, since I always hear people saying silly things like "hp puts you into the wall & torque puts you through it" etc. that really don't make much sense

As far as whether a 8k rpm 5L would be better than a 7k rpm 5.7L shortblock, there's too many variables to just make a blanket "sure thats better" judgement . Like everyone else said, way too many variables & compromises to make with a street car .

cndctrdj

i was just thinking it kinda like an indy car. they have a large bore small stoke and spin to 19k rpms. they make all the power in the world but arent very reliable. if we can do that with our motors but on a smaller scale, we could, with the right cam, have a smooth power band high output and smaller gears for better acceleration. and still have pretty good reliability also.
to whoever said you would need to rev the motor out more to move the car off the line, dont you have to do the same thing when you put a big cam in?

Seal

you can always put a 4.6 stang engine in there if u wanna destroke :P

Camaro_Maniac63

Indy cars, and Formula 1 cars for that matter, use a large bore small stroke not because they want to, but because their sanctioning bodies mandates them to 3.0L maximum displacement. I am pretty sure if they had an option, they would choose to go with larger strokes on their racing engines as well.