ZCHARGE

OK I've got a problem that has me stumped. I have a 95 Camaro Z28 with a 9# powerdyne supercharger. when i smash it and hold WOT i've got awesome power and then it like breaks up or flutters around 5,000 RPM's. I just installed 30# injectors and its still doing it. i've also replaced the optispark, plugs and wires, and the vaccume harness to the distributor, still no change. If i let off just a little it will stop breaking up and then i hold it wide open again and it pulls hard clear up to 6,2000 rpm's. But threw the initial power curve up threw the RPM's it usually breaks up around 5,000 for like 2 seconds and then goes back to normal. I have a MSD ignition box which i unhooked and pluged back in the stock ignition, still no change. Alright guys what am i missing? its probably something simple and im gonna feel stupid. I keep thinking the MSD has gone bad and my stock ignition isnt hot enough for the supercharger. any input will be greatly appriciated.

fireman

So your running 9lbs of non-intercooled boost on a stock motor?

What do your plug wires look like?

We once wired the inline pump wrong and the power would break up at anything over half throttle.

Get a fuel pressure gauge on it and see whats happening.

RMC

I'm hoping you're not spinning it up to 6200 with 9psi on stock and especially without scanning or having any real data to diagnose problems.

But I don't know, you didn't tell us. So what's your setup?

Is it stock or aftermarket valve springs?
Stock fuel pump with just an inline?
Colder heat range plug?
Timing control or pulled out with programming?
Any data logs?

more info please

ZCHARGE

no i normally shift around 6000 rpm's and i hardly ever see 9lbs of boost. i had the computer tuned, we took out a couple degrees of timing to get rid of some knock retard, but other than that everything seemed in order. i have stock valve springs, inline fuel pump still running the FMU even with the 30lb injectors, yes colder range plugs, my wires are brand new just put them on. i believe i may have pinpointed the problem. yesterday i noticed a little chatter comming from the drivers side on the motor. this must be new cuz i've never noticed it before and i really pay attention to engine noise. so my guess would be a lifter gone bad, maybe a bent push rod, or a faulty valve spring. what do you guys thing???

RMC

I'm not really certain but that sounds like you were getting valve float which has now progressed to at best a bent pushrod..worse a lifter problem.

Valve float is where your springs are too weak for the application and don't have enough pressure to fully close the valve. While the cam is rotating "up" the ramp of the lobe the valve is opened but cannot close as fast as it needs to as the cam rotates to the "down" portion of the lobe. While the cam continues to the base of the lobe a tiny gap is created in the system instead of everything riding tight against the profile of the cam.

Think of it like two people on a trampoline jumping out of sync. If you just stand there while the other person jumps you'll move up and down as long as you stay in contact with the trampoline. As soon as you make even the smallest amount of space between you and the trampoline when you come down it feels like you are crashing into it. Under heavy valve float conditions the valve is open too long from the weak spring and the lobe / lifter basically drops out from under the pushrod. The two in turn crash back into each other out of sync and thus cause bent pushrods or broken lifters.

Hope it checks out OK for you. Check on your valvetrain before you do anymore extreme testing and if it's OK try to get some fuel pressure readings when it's acting up to make sure it's not a problem with that.

More importantly start saving for stronger parts better suited for your setup. Eventually that means pistons, crank, springs, cam, lifters, pushrods.

Good luck,
Ross