ok so i just got my car off of the dyno for a speed density tune and my tuner was complaining about the car missing at high rpm's. its a ls6 stroker and has a patrick g speced cam. i took it out tonight and was messin with it and it seemed to happen around 6200 and the cam is speced to pull to 6800 but i cant pull it that far because it starts to miss. it almost sounds like im bouncing the rev limiter. i tested it in 4th gear so my tack shouldnt have been slower. it also has all brand new PRC dual vaulve springs .660 lift so i dont think it would be trying to float the vaulve.
and it only does it when there is a load on it, and what i mean by that is that i can rev it up in nuetral and it doesnt do it.
thanks for the help.

 

What rocker arms are you using? It sounds like valve float...

Are you sure its not a fuel related issue?

Shane

 

stock rockers, damn....

 

cmon now somebody

 

Im assuming LSK lobes....

How are the springs set up?

 

PRC dual .660 lift

 

Check your fuel pressure like Shane said.

 

Does sound like it's lacking fuel. You can hook a guage up to your fuel rail and see if it drops when it cuts out. Should be about 40 I believe. Maybe time for a 255lph pump and injectors.

 

Supposed to be 58psi.

 

fuel is good my tuner said, im wonderin if it is my valve springs.

 

your up to 200 bucks you owe me.

 

you better buy an intake with it

 

its still doin it and havent figured it out..........................................
im thinkin it might be some weak springs...

 

How are your springs setup?

Installed height? Or distance from coil bind?

 

i dont know man, they are PRC LS6 heads and they were set up by TSP

 

It didn't do it on the dyno, but does on the street with load? What'd the dyno graph look like in the higher RPM's? What spec on the cam?

 

hey matt i tried to call yall today but yall were at lunch...... anyways, yea it does it on the dyno too with a load on it. the cam is a 246/253, .622/.621 112+4 LSA, i dont know what the dyno graph was doin cause as soon as it started doin what its doin i got out of it, the cam was speced to be shifted at 6800 rpms
Thanks,
Austin Rich

 

TTT for a new day

 

it's gotta be one of three things, hook a vacuum guage up to the intake and go drive it while it's messing up if you see vaccuum drop off big time, you have valve float, it sounds like a fuel problem, but if he has checked fuel, this is the next likely option, let us know what happens

 

If it only does it under load I would check ignition, rev limiter, plug gap, wires. When it was on the dyno did they see any miss firing with the tuning software? With valve float I didn't think your engine missed I thought it just stopped making power.

If it was a fuel problem I would think the AFR would change during the dyno run giving you clues.