Had my car on the Dyno and I'm having a strange issue, car made 428hp/494tq...the hp hits 5k and just flatlines and holds right around 430hp till 6k where we let off, peak tq was at 3900/4k...I knew the valve springs were tired so I put new pac springs on and it didn't change a thing. I changed cams over winter and I'm starting to think the cam is off a tooth, even tho I was very meticulous with installing it. I'm on my phone right now but will post a screen shot of the graph when I get to a computer. Any other ideas or input?
370ci lq4
Tea stage 2 243 heads
Si5 cam (231/237 112+4)
Fast102
Nw 102 tb
Built 4l65
Yank 3600
Xpipe
85mm maf
FTP lid

The car is down about 30 - 40 hp, could the cam being off dot to dot kill hp? Or does it just shift the curve?
Have to figure this issues out ASAP.

 

Even if things are off from your install it should not be peaking that damn early lol. Sounds like something is off on that dyno maybe

 

im starting to think that also.. even if the cam timing is off it would peak earler and fall off... he ran it out to 6800 on the run after the valve springs and it was flat almost exactly the same.

 

I wonder if it's the cam...mine is a 230/238 113+2 at peaks at 6300 in a 5.7l

Yours is a similar size cam in a decently larger engine which will bring the RPM peak down but it is also a 112+4 which will also bring it further down. I would think it would be higher than 5k but wouldn't expect it to be over 5900-6000 peak.

Normally my next thought would be intake or exhaust restriction but your mods there look up to par. Any chance the transmission is slipping under peak HP (I would expect it to slip under peak TQ if anywhere though)?

EDIT: you beat me to posting with the graph, that doesn't look right at all...looks like it flatlines well before 5k rpm.

 

Trans and yank 3600 are fresh and Trans fully built, has a few hundred miles on it

 

Yeah I mean you are peaking way sooner than even a bone stock LS1 would, so I can't even possibly comprehend how it would be the cam or any of that. If you could find another dyno for a cheap quick pull it would be interesting to see if there was a difference

 

wheel spin? are your straps tight?

 

What did the AFR look like? Timing? You don't have a rubber silicone part in the intake sucking shut do you?

 

I would think the straps were tight, also have et streets 275s 17s

 

the in car gauge was reading 12.9/12.8 for afr and timing was 28*

Alvin i dont believe the rubber was sucking shut its only a short piece and its a pretty thick rubber

 

To kinda skip past the dyno questions... how does it feel on the street?

 

well i didnt drive it all winter and over winter i swapped out the old cam (228/230 .578 112) and put under drive pulley on put in built trans and yank3600 (took out edge 3400 which was real tight). To me it feels great and feels like it pulls strong. im hoping to go pick it up tomorrow and if the rain holds off i will run it at the track to see what she does.

 

Yes the track will tell the real tale

 

After seeing those ridiculous torque numbers like that graph is showing, it's blatantly obvious the dyno is fucked up. You might have an issue with your engine, but don't base that upon that graph. Get your money back and go somewhere else.

 

That cam should pull all the way to 66-6800. My buddies LQ4 setup with a 228/232 cam peaked at 6500, he also had crappier heads and a FAST 78 intake...

 

Did you degree the cam when you installed it?

 

No just dot to dot

 

I will be getting it back soon, I plan on making a run on another Dyno just out of curiosity and see what it does at the track

 

Almost 500ft lbs to the tire?

 

Thats what it said, Last year with a 228/230 cam it made 440/450, I didnt believe the tq numbers right away... I can't wait to get this car back and see how it runs at the track and roll it on another Dyno