Tims 88GT

Hey guys I am having a mid rpm like 3k and up pre ignation problem. Timing is like12, fp is 46 withvac off. I can not figure out how to get it to stop. I added a lot of fuel and a lil timing. still does it. I do not know what to do next. I do not have a CEL. Mods. Lunati cam, afr 165 head, 24lb injectors, 80mm maf calibrated for 24's, 190lph fuel pump, aeromotive AFPR. thats about it.

mattdel

any air leaks at all? intake gaskets, intake tube, vacuum,

67mustang302

Also what is your compression ratio and what are the specs on the cam, and what fuel are you running?

Tims 88GT

compression is stock. cam specs do not have anything to do with this problem. I have used it many times. in a blower motor as well, never once had a problem.

67mustang302

If you think cam timing has nothing to do with pre-ignition and detonation, then you don'tunderstand pre-ignition and detonation. Your intake valveclosing point has a direct effect on your dynamic compression ratio. There's a reason I asked what the cam timing was, and what fuel you're running. And is your static CR stock, or close to stock? Different heads/gaskets will change it unless they have the exact same chamber size and exact same gasket volume. Also, how do you know it's actually pre-ignition, and not just detonation?

samseed101

That was going to be my question as well. Either way, try running a colder spark plug...maybe one range colder. Also, you may have carbon deposits that could contribute to both conditions. Glowing carbon deposits can stick to hot exhaust valves and cause pre-ignition. Carbon deposits also form a heat barrier. And they can raise compression. A little seafoam could take care of carbon.