Good numbers,

That one was done on that off brand dyno and I remeber that guy got a lot of **** for that. Would have been better if it was on a Dynojet(apples to apples), but good numbers anyways. One thing you can tell is that software that dyno runs has some serious smoothing going on with the power curves, big difference from most Dynojet sheets you see. Looks a lot like a Superflow chassis dyno printout in comparison.

Bret

 

Isn't big horsepower about getting a lot of air into and out of the engine? And isn't the main determining factor (once the easy stuff has been done) the flow of the cylinder heads?

If you've played around with any of the commonly available computer-simulated dynamomenter programs it becomes apparent real quickly that if you shove a 383 in place of a 350 short block, peak HP doesn't improve much, all else held equal. Low end torque jumps quite a bit, of course. But a 10 second race motor doesn't spend much time revving though the low RPMs. It's set up to jump straight to peak torque at the line (converter selection) and shift maybe 500-1000 RPMs beyond peak HP. In short, big HP up top is how to go fast in a real race setup. That only happens with LOTS of airflow.

Maybe I'm way off base here.

I'll note for the record that I build STREET engines exclusively (and I don't earn my living this way, either- just a hobby and passion of mine). Extra cubes make a big difference in the world of street engines where torque the main goal. Especially against a low 2200 stall converter. But for racing where life BEGINS at 4000-4500 who cares about low end torque? Build as much HP as you can and then gear and converter appropriately.

 

holy freakin crap joe..........thats about as close as it gets!

 

Great post.....

That's why on a M6 car you could build a cheaper 355 and still do extremely well with it. Cause you can launch the thing at 5000rpm and only stay in that top 2000rpm band where the 383 doesn't have much of an advantage UNLESS you have some crazy cylinder heads.

Another good reason for a 383 over a 355 for street use is that the 383 will eat up more camshaft and stay driveable. Then again the 355 with the same heads doesn't need as much camshaft.

Bret

 

But..383s dont have less HP than a 355 right? They just might not have enough more to make the bigger pricetag worth it correct? If you are arguing for price I agree, but if not you are arguing the "no replacement for displacement" theory. But I think you are strictly speaking in funding terms.

 

Same heads, same relativly high HP peak and different cams, it's possible the the 383 might be down a few ponies.

Bret

 

355 ,383 with "same" cam and "same" heads hp and moreso torque is better with the 383.....on that level all things being the same yes 383 doesnt have much on a 355...now on the other hand there again using the heads being "same" a cam change to optimize each combination the 383 surely will be higher hp and torque unless the heads are holding back the air flow the 383 wants...If the heads are up to par then you would see a noticeable difference between the two...

 

update- my car went 11.94 @ 119.84 yesterday with the tune from my cousin's car. i was hoping for 120 but i tapped the rev limiter at the top of 3rd and only got 2 passes in due to other issues.

 

Nice numbers Rumair!

beats my 114mph N/A on a 11.85!

 

thanks...i'm hoping there's more mph there with some more tuning (won't be back at the track until after i fix whatever's wrong in the drivetrain). i can probably get a little more ET with less air pressure in the nitto's and 4500-5000 rpm launches, but that won't matter since i'm not legal anyway.

 

Ah just toss a bar in it and have at it. I notice my car is more stable with the bar

 

hehe...i'm not trying to spend any more money on this chebby powered car anyway. i've already got a "real" race car.