[69CamaroRacer]

Ok so I have this 383 with about 1500 miles on it now and I took it to have it dynoed and the best they could get was 337 hp to the wheels on a Dyno jet. We base lined at 304 and found that the msd Dist is was only advancing about 10*. we played with the springs with no avail.. so we set the initial at 28* for a total of 38* all in at 2800 rpm.. That change netted a gain of 20 rwhp and after a few more timeing adjustemnts we got the number up to 331 rwhp. Then we started playing with the rear jets and went to an 82 rear jet and 72 main. Our air fuel ratio was pretty flat at 12.7-13.0 throughout the run... So over all I would say that I expected more than 404 hp out of this combo. I think that i am in desperiate need of a cam change.. as the power is starting to nose off at 5800. THe cam is a comp magnum with 236 in and ex.. and 286 advirtised .. Mayby Eric68 or someone else who has some expirence can chime in here and give me some pointers

[camaro_fever68]

You could handle some more cam. You got the CR, heads, and intake. With 230*@0.050", you cutting the combo short. You could go up to the Comp XE 294HR with your combo. That'll give you 242@.050" and it calls for a 3000 stall also.

[69CamaroRacer]

the dyno is showing that the converter is stalling somewhere around 4200-4300 rpm

[camaro_fever68]

If your converter allows then, you could got up some more to the XR300HR and get a lot more. Your CR is still good as it calls for 10.0:1 and a 3500 stall. If you got power accessories, they will be greatly affected though. Your idle will be around 1200 also.

[GOSFAST]

The basic pump-gas 383's we deliver make from 480 HP to 500 HP maximum with the same cam installed. We build this on a 234/242 @ .050" x
.540"/.560" x 107/108 C/L. All these units make peak HP @ 6100/6200 RPM.
This a retro-hydraulic, 10/10.5 C.R. (pump-gas) with Brodix/Pro-Topline heads using 185/190 cc runners with 2.020's and 1.600's and a set of 1.750" headers. They run with a total of 34 degrees timing and will sit and idle at 850/900 RPM. These are not any type of "fancy" units. Thanks, Gary in N.Y.

P.S. We can make 450/460 HP with the "Austrailan/Chinese" heads, which keeps the budget somewhat lower. We have gotten absolutely no good results whatsoever with AFR heads, SB or BB.

[Eric68]

There is nothing wrong with your cam IMO. Your combo is sound, should work well as is.

How did you determine your compression ratio was 10.5:1?

What valve springs are you using? What is the installed height and pressure?

Is the tranny fresh? Is the fluid nice and clean?

[SIDEWAYS]

Whats up w/the distributor? Do it have the right advance bushing?
The MSD comes w/the slowest curve fromt h factory so people don't blow their motors up. Maybe its still setup that way?

[69CamaroRacer]

Originally Posted by Eric68

There is nothing wrong with your cam IMO. Your combo is sound, should work well as is.

How did you determine your compression ratio was 10.5:1?

What valve springs are you using? What is the installed height and pressure?

Is the tranny fresh? Is the fluid nice and clean?

Eric this is what I know for sure... I did not build the engine but I told the shop that I wanted 10.5-1 so I am assuming that is what I got.. It does sound like it has alot of comp because it has alot of pop at idle.. I know that is not a good way to tell but..... Now for the springs the springs are the upgraded springs from AFR good for .600 lift ... they have an installed hight of 1.550. I really do not know the spring presure.. Now about the tranny everything is new... new trans.... converter... I am using a full synthetic .... So why do u think that I am off... am I wrong to think that I should be making more power??

[onovakind67]

These numbers are very typical of a mild 383/TH350 on a Dynojet, with a 20% loss equates to about 420 fwhp. After you factor in all the accessories and exhaust losses, I'm not surprised by the numbers. We get some of the "440" hp crate motors making less than 300 to the wheels.

We got about the same rwhp @ 6000 rpm from our 331" SBC with IE heads, a 228° Comp SR cam and a 2-bbl carb with a 4-speed tranny. Are you running appropriate headers and a functional exhaust? I would consider the exhaust system to be fairly important.

I wouldn't calibrate the stall speed on the dyno as it is much heavier than your car.

[ProdigyCustoms]

Don't put a ton of faith in any chassis dyno, especially with a automatic transmission and a stall converter. Chassis dynos are tuning tools only to do exactly what you did, develop a baseline, and tweak to lose and capture HP. But don't be surprised if some of the things you do on the dyno, that add horsepower, actually slow the car down at the track.
Don't be so disappointed by your numbers. I took my street racer to a chassis dyno for the first time in 6 years. it made 414HP. problem is the car runs 10.70s at 3450LBS, which takes 600FWHP, or 500RWHP. We puts with it, found 15HP reducing the timing, and slowed it down 1/10th at the track.
My advice, tune it at the race track, it's more accurate, cheaper, and a hell of a lot more fun. Don't get attached to dyno numbers.
You gonna paint that thing or what?

[pdq67]

onovakind67,

What's "IE" heads, cast-iron? OEM or what??

I've never heard of springs installing at 1.550",? Do you mean 1.550" diameter BB -type springs instead??

And too much spring on a hy-cam will callapse the lifters at speed..

Something just isn't right here, and I want to close by saying that I WOULD NOT buy anything w/o a spec/build sheet OR else I would tear it down and reassemble it before I did anything with it so's I would know what the heck I bought!

pdq67

[onovakind67]

IE = Iron Eagle

[camaro_fever68]

Originally Posted by 69CamaroRacer

Eric this is what I know for sure... I did not build the engine but I told the shop that I wanted 10.5-1 so I am assuming that is what I got.. It does sound like it has alot of comp because it has alot of pop at idle.. I know that is not a good way to tell but..... Now for the springs the springs are the upgraded springs from AFR good for .600 lift ... they have an installed hight of 1.550. I really do not know the spring presure.. Now about the tranny everything is new... new trans.... converter... I am using a full synthetic .... So why do u think that I am off... am I wrong to think that I should be making more power??

Your combo is doing everything it should be doing. The cam your using is good for 6000 in a 350 so falling short at 5800 in a 383 in normal. The other thing to look at is what kind of exhaust do you have? Your using a single single pattern cam and if you don't have exhaust optimized, it will hurt you some. Do you like the way the car runs now? Do you want more driving power? I wouldn't worry about dyno numbers if your happy with the way the car runs while driving. If you want more power though, cam is the place to go and if you have full exhaust, run a dual pattern.

[Eric68]

If you don't know your engine specs for sure its impossible to tell if your combo is making the power it should or not.

Personally, I think it sounds a little off based on your assumed specs.

I say go run it at the track and see what kind of MPH the car pulls.

[Doug F.]

My old SBC which was a 383 with ported Dart II's and a mild solid roller only made 335 on a dynojet. I thought that was pretty poor but all I cared about was the track. At 3550 lbs it went a best of 11.90 at 113. Maybe not that good either, but there we're too many street cars much faster.

But I saw a lot of "450 HP" engines running 13.0's.

Get it to the track.

The chassis dyno is always disappointing.

btw, I've tuned many NHRA stock eliminator cars on the chassis dyno. They obviously have the drivetrain optimized, but 400 RWHP on the same chassis dyno with some of those cars goes 10.50's at 126 at 3200-3300 lbs.