The last 2 times I've been to the track I've experienced this, but last night it really made me wonder.

Quick synopsis: T56 swap, 27" BFG DR's, 3.23 rear, intake, catback, tune, 159k mile original LT1. Every time I race, I'm getting more and more MPH out of the car, but going though the traps (3rd gear at redline - 6k) I can hear the motor breaking up. It starts breaking up at about 5300 or so, up to redline. I'm trapping over 106 MPH now, so its making power up top, so this confuses me.

First impression - possibly ignition, but no other symptoms to verify this, and the ignition system is relatively new in its entirety.

Second thought - valve float? It is a 160k mile engine that I've always run hard.....

Could also be fuel, but I had the injectors cleaned about a year ago. Pump?

Help me get started in the right direction!

 

everytime I've had an ignition issue up top it's not just a light missfiring, its like hitting a wall. Been through bad plug wires a bad opti and a cracked plug, all were very noticeable. I hit valve float at about 5600 when dynoing my new engine combo, again power fell off real quick and didn't sound good either. No other symptoms like hard starting, stumbling, etc?

 

None. The car runs like a champ, better than it's ever run. That's what's stumping me!


It doesn't fall on its face, but it doesn't pull up top when I hear the sounds either. It kinda flattens out, which leans me to valve float.

 

im having the same problem its high-voltage cap and rotor, look into this

 

I'm not sure what you mean by this...OEM opti's are good for even some killer race motors so spark shouldn't be a problem unless the opti is actually going bad.

 

I'm going to get a FP guage today and see if it's fuel related...

 

Bump for more opinions...

 

Anyone? I'm having the FP checked this weekend at WOT simulating the problem but I don't think that's it.

Anyone know how to tell if you're getting valve float for sure?

 

Like does it make crackling noises at those RPMS? If so I had similar issues. Popped in a new opti (original had 158k on it) and it cleared it up. If you can find a way to test your opti to make sure before you pull everything apart, go for it.

 

I had the exact same problem and it took me over a month to figure it out. Mine was my plug gap being set to big. Reset my gap and it quite. Also check you wires might be arcing with the higher voltage at higher rpm

 

i had a similar problem, it started out as a miss every once in a while around 6k then it progressed to what felt like a rev limiter at about 5500. it took about 6 months to get to that point and i have fought it for that long trying to figure it out. i changed opti, plugs, wires, and coil. i blew both head gaskets in the process. turned out to be an auto zone icm, wich was fairly new. put the oem on and it hasn't missed a beat