This is my problem....i ran my car on the dyno a month ago...it was having timing problems, pulling timing out on the top end of the dyno run.........they diagnosed the problem as my stock ported mass air ends, i replaced the ends with a pair of stock screened ends and ran the car on the dyno last week again and the problem still occurs......i replaced the optispark so i know its not that...........The performance shop thinks the car might be carboned up real bad and suggest i run some C-foam through it to de-carbon it.....its pulls the timing out at 4500 rpm, starting with only 4 degrees, at 5000 rpm it is pulling out a whopping 8 degrees......anyone ever heard of this? or had this happen to them?
any help will be great, these are my engine mods:
160 t-stat, airfoil, TB bypass, MSD coil, taylor wires, moroso CAI, stock mass air ends, cutout, LT4 knock module, power pulleys

what should i start replacing?

 

You mean your KS is pulling timing out, just tune it out or put some more teflon tape arond the KS & it wont' be as bad, lots of these LT1's have this problem, I ZEROED my Knock Tables out completely.

 

not to sound like an idiot, but what is Zeroing your knock tables?...is that done while tuning?

 

wouldnt my LT4 knock module not allow for timing to be retarded?

 

The LT4 knock module is "tuned" to be less sensitive to the noise created by the HD timing chain and roller rockers the LT4 engines came with vs the standard knock module for Lt1 engines. It in no way will stop timing from being retarded.

Brent M.

 

Put the pulleys back to stock and try again. I've heard that some aftermarket pullies set up a resonance that is sympathetic to the knock sensor tuning.

If that doesn't work, empty the fuel tank and fill up with 100 octane unleaded race gas. If the timing problem still occurs at this point, you can reasonably assume it's false knock.