Bummed about by 383 dyno performance.

I finally had my 94’ Camaro dyno tuned today after being done and sitting in my garage for 3 years, and I was pretty disappointed. I know that all dyno’s are different and it’s not the best way to measure power but something seems off. The car ended up putting down 361 hp and 390 tq at 5600 and 3900 respectively.

The LT1 is a 383 with a forged bottom end, GTP stage 2 heads, GTP 6 Cam (similar to the cc306), 1.55 roller rockers, 54mm TB, 30# SVO injectors, TPIS long tubes, catback to a flowmaster with no cats, Street Twin, T56, and a stock 10 bolt.

I was under the impression that this cam was supposed to pull to 6200-6700. The power line gets wavy right about 5600 to 5800 and then starts falling off.

Could the valve lash be too tight? I am confused as I was estimating peak HP to be somewhere in the low 400’s.

I will try to post the dyno sheet when I get it emailed.

I have the dyno sheet but am unsure as to how to post it.
Thanks Colin

Could the cam be off a tooth?

Here is the graph, check it out.

http://i443.photobucket.com/albums/qq154/c-balke/camarodyno.jpg

Host the dyno sheet on www.imageshack.us = then use the link provided to post it here.

You should be getting more rpm out of it, looking at the sheet will help.

If you cannot get that to work, email it to me


ehh...beat me to it while I was typing

I don't see anything obviously wrong with that graph like ignition, valve float, VE or other...

What is your compression at?

It's been a long time but the compression should be up around 11/1 if I remember correctly.

I am thinking that maybe the cam is off a tooth because it makes tons of torque early and then falls out early.

If it was a tooth off, it would run like crap - not just move the powerband around. What are the actual specs of that cam? Did you have the intake ported to match the heads?

Yeah the intake was ported and port matched. The cam is 235/242 @.050" with lift of .568"/.592".

Flowmaster cat back can easily choke a motor down.

ya but is shouldnt be that bad.

On the bright side you torque isnt that bad.
What did the heads flow? How much work does stage 2 consist of?

The second pull (in red) was with the cap off. It shows how much the flowmaster was holding back, but it still should be making more power than that.

GTP Stage 2 - Competition valve job, 2.00/1.56 valves, fully ported and polished then flow bench tuned for 280/210cfm

My flow numbers were supposed to be 278 and 210 @ .650

Do you have a ewp, 58mmtb, etc? I.e. all the supporting mods?

That is way too early a hp peak for that cam. Something in your intake tract is probably causing a clog. For whatever reason, your engine just stops making power and noses over. Did you verify that the throttles were wide open when your foot is on the floor? No floor mat stopping it about 10% shy is there?

About these heads of yours, did you buy them from gtp or were they second hand.... :think:. There is a lot of bull**** going on out there with people passing off heads as reputable porters work and them just being cartridge rolled bs with chinese valves in them.

It would be great to see a datalog of the dyno run but i doubt you have that.

Yeah it has all the supporting mods (I have most of them listed in the first post). The heads were purchased directly from GTP so they are legit. I spoke with Craig today and he agreed that maybe the cam is off a tooth or maybe the valve preload is too much. I did not hear any popping in the exhaust or backfires, that would lead me to believe that the valves were hanging open.

If you look at the torque curve and how much power it's making so early on it seems like it's running an RV cam. hehe

I will try to get the data log and check out the TPS readings.

Check out the map readings too that will give you an idea if its something in the motor or if something in front of the tb is causing the problem. Get your maf airflow in grams per second as well, peak number will be what to look for. I have seen enough of these run that i have an idea about what it should take to make x hp.

Off a tooth would have you 16-20 degrees advanced depending on your timing chain, I really really think you would know for certain if it was off that far. The results would be horrific. Cranking compression test would reveal this most likely.

I am guessing you are also certain that the valve springs are up to the job since both pieces are gtp stuff.

Assuming everything is right, and you haven't killed compression, that engine 'should' be capable of numbers well north of 400rwhp.

Take it to the track, if your AFR and timing is right who cares what the dyno says? You built it to have fun with and thats all that matters.

My neighbor has a LS1 Camaro that wheel dyno's at 400rwhp and he always bragged himself up on this number and how crazy I was to do an LT1 car. Long story short, he hasn't beat me yet and my car is just barely at 300rwhp and trust me his car has ALOT more into it than mine does, it drives him nuts.

Probably not off by a tooth, but if the cam was not degreed as part of the install, it may
very well be off +/- 6* which would cause a significant loss of power up top.
Overtightened rockers, gaskets protruding into the passages could also cause you to be down on power.

Also keep in mind that larger displacement (in this case 383) will tend to squeeze the operating RPM.
A cam designed to peak at 6200 for a 350 will peak much lower (5600ish) in a 383.

Alright, I did a compression test and everything looked good to me. All cylinders came in between 195 and 225.

I have a call into my machine shop to verify that they degreed the cam. But I am planning on pulling the timing cover this week to take a look anyway.

I am going to attempt to put an old version of free scan on my laptop and get some map and maf readings for you guys.

Thanks for the help.

:yes:Take it to the track, most a4's lay down low numbers. It may run low 12's/high 11's, yougot to run it to find out tho.

you built a crappy engine. throw it away and start over :)

i wouldn't be too bummed, i had the same issues with my 94 camaro w/ 396. 355hp and 381tq on a dynojet. A few months later I dynoed on a mustang dyno and get 345/365. The only mods i did before the mustang dyno runs was replacing the slp loudmouth w/stainless works chambered muffler to a magnaflow catback and a cutout. I have the CC306 and it peaked at the same RPMS as yours did. The car has run strong for 15K and never skipped a beat.

my buddys 02 Z 6sp dynoed at 389 and 376 on the same dynojet dyno with only mild thrunder racing cam,CAI, longtubes, catback w/cutout and 4.10s. We raced on DR's froma roll, still beat him by a car length while not hooking up in 1st or 2nd with 315 goodyear DR's. So i knew the car was perfroming near what it should.

Even with what i thought were crappy #'s i still did 133mph in the half mile at the sandhills open road challenge, same as an 06 mustang GT with the saleen SC.

get out there and take it to the track, you won't be dissapointed!

i wouldn't be too bummed, i had the same issues with my 94 camaro w/ 396. 355hp and 381tq on a dynojet. A few months later I dynoed on a mustang dyno and get 345/365. The only mods i did before the mustang dyno runs was replacing the slp loudmouth w/stainless works chambered muffler to a magnaflow catback and a cutout. I have the CC306 and it peaked at the same RPMS as yours did. The car has run strong for 15K and never skipped a beat.

my buddys 02 Z 6sp dynoed at 389 and 376 on the same dynojet dyno with only mild thrunder racing cam,CAI, longtubes, catback w/cutout and 4.10s. We raced on DR's froma roll, still beat him by a car length while not hooking up in 1st or 2nd with 315 goodyear DR's. So i knew the car was perfroming near what it should.

Even with what i thought were crappy #'s i still did 133mph in the half mile at the sandhills open road challenge, same as an 06 mustang GT with the saleen SC.

get out there and take it to the track, you won't be dissapointed!

I couldn't agree more with this statement. Once you get track times you will see were you are truly at. In my opinion dyno numbers should only be used for base runs and tune from there to get the most out of the tune. What the actual numbers are and what dyno it is really isn't worth a hill of beans to me. Course we all know what opinions are worth. Just saying (a dyno to me is for tuning not bragin).

That being said. What is your A/F above 5500rpms? My SVO #30 INJ leaned out bad after 5400 rpms. I just can't believe that those injectors would be holding you around a 13.0 +/- .2 above 5500 rpms based on my own testing on a wideband with my car that has a similar set up with less lift in the cam.

Also I agree with the MAP statement above too. See what your MAP readings are above 5500rpms. I bet somewhere BTW the MAP and AFR you’ll find your culprit. That's where my problem was when I was traping 87.5mph and am now traping 91mph consistently in the 1/8th with a few more bugs to work out in the tune and shift points(not to bad for a little of the shelf grind).

Just a word of encouragement. Take this as a hobby. The difference with folks who run great times and folks who don't regardless of the set up are the folks who run the good times have spent a lot of time figuring out and fixing the numerous little things that make that set up max out it's potential. Yes there are a few folks that get everything set up correctly the first time out and are kinda lucky if you ask me and yes some set ups just won't run but those are far and few in between. G/L and post up the answers to these questions and we'll get you on the right track.

You trapping 91 with the 306 and stock heads?

You trapping 91 with the 306 and stock heads?

Check the link below to keep this on track with the original question posted by the OP. I think it will answer your question sufficiently.

http://www.camaroz28.com/forums/showthread.php?t=647907

I think your cam is way too advanced, those compression #'s are high for a street motor.

I have the same compression, about the same heads..and a little bigger of a cam....I put down the numbers below. Did you throw a scanner on it and see whats going on? Fuel pressure ,etc... all that jazz...my first dyno on my new motor i put down 389rwhp and was pretty pissed...it ended up being it was running a bit rich and had a lot of false knock. Dig deeper, you should be 405-415 rwhp'ish

I have to agree with those saying cam timing. You never indicated it was degreed or not.

something changes right around 280-290hp, not sure what RPM that is, both HP and Torque seem to take a hit towards the flat side. That's about all I have to say.