Dyno'ed the 383 today

[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 someone who has some expirence can chime in here and give me some pointers. I was really looking for 400 at the wheels...

[gsxrken]

What heads do you have? What compresion ratio did you end up with? Auto or stick trans? Intake manifold? The reason I'm asking is there alot of reasons you might be signing off at 5800. 400HP at the wheels means 500HP w/ 20% parasitic loss. If you have a typical 383 street build, I'd say you are right about where you should be. What was your torque like?

[69CamaroRacer]

Here is the combo 383 ci, 10.5-1 comp ratio, 195 AFR, Comp 286HR 236 in and 236 ex @.50... Holley 750HP

[speedster]

Here is the combo 383 ci, 10.5-1 comp ratio, 195 AFR, Comp 286HR 236 in and 236 ex @.50... Holley 750HP

It sounds a little low, but not out of whack. One of my boat engines that dyno'd at 430 crank hp (at 5900 rpm) was very similar:
355ci, 10.3 CR, 195cc TrickFlows, Comp 232/[email protected] .483" Lift 114 LC Hydraulic, Crane 1.5 Roller Rockers, Holley 750, Edelbrock RPM Intake, Stainless Headers, 36 deg advance.

A couple of things you may want to look at:
- Do a compression test on each cylinder. If I remember correctly the engine above was around 170-175 psi.
- Check your valvesprings. Since it looks like you are running a hydraulic roller, if the springs are not 100%, you may be starting to float at 5800, those lifters are very heavy.
- Is that A/F ratio for one bank ? if so, do a quick plug reading and make sure they all look the same.
- If those all look good and your valvesprings can handle it - beg, borrow or steal a set of 1.6 ratio rockers. You may be suprised at the jump. Someone with a similar combination netted 37 hp by that rocker change.

Just my .02 on things to try

[speedster]

Also:
Is your car a stick or auto ? (e.g. any possible tranny slip)
Were you running a full exhaust ? (e.g. any possible flow restrictions)

[ProdigyCustoms]

This is a copy of my post on the Camaro board

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?

[69CamaroRacer]

Car is an Auto with a big stall... dyno is showing 4200 stall.. but I think that it a bit much it should be more like 3500....

The exhause it 1 3/4 full headders and 3 in into an x-pipe all the way back to 40 series flows.. I was thinking that flows might not be best for power but maby I am wrong....

Frank ... I want to do the car but I have been buying abot of property lately so I think my money is gonna be tied up for a while... I have bought 2 houses in Feb a little med style 2/2 1100 sq ft in destin, that is gonna be my rental and then I am having a 3000 sq ft 4/3 built in Crestview..(remember that city where u got off of I-10) I just have not been able to stomache pouring money into a depreciating asset like a car when I can buy houses that I know will make me money...

Anyway I am gonna have a track day soon so I will let you know what it runs

[ProdigyCustoms]

The exhause it 1 3/4 full headders and 3 in into an x-pipe all the way back to 40 series flows.. I was thinking that flows might not be best for power but maby I am wrong....


Thats plenty of exhaust, thats more then I run on the street racer, I ran 1 3/4 and 3". no X pipe, although that is changing this week as we are changing the frame, headers, exhaust, etc. Also, I am taking the engine, in it's exact tune as the rear wheel dyni, to a engine dyno to see what the difference is, i'll let ya know.

[69CamaroRacer]

Frank I will be curious to see what the difference is... so do u think that I have too much exhaust??

[ProdigyCustoms]

no i do not