I just finished up a heads and cam swap in my car and I had it on the dyno for the first time last saturday and it was ping/stuttering/knocking or something on wot right at 4 grand every time.

My tuner couldnt figure it out but he said it might be a bad plug or a blown head gasket. A mechanic I know told me to smell my oil for coolant and there was no hint of coolant so I don't think the head gasket is the case

Do any of you guys have any suggestions of what this could be? I also heard from someone that my rev limiter might be f'd up and its trying to kick in at 4 grand. Never heard of that but its a possibility.

 

Motor specs? what heads,cam, valve springs, comp ratio?

 

patriot ls6 heads 228r cam 11.1 comp(wasn't bad gas) patriot springs 7.400 pushrods

 

What was the A/f ratio when it was doing this on the dyno? Stock injectors?

 

Stock injectors. My tuner told me a/f was right where it should be but I don't know the exact number. We narrowed it down to a computer problem, spark, or internal but it had my tuner at a loss of words for why it was doing it

 

I would say spark. If you had an internal problem it most likely would cause problems before 4k or at least not do it consistently at exactly 4k. And A computer problem would have showed up before you did the h/c swap.

 

This is the first time I have had it on a dyno but I am pretty sure it has done this before the swap but not consistently. It also only does it at wot. I gradually took it up to 5k and no ping

 

I would eliminate the spark option first as it will be the easiest to prove. Ohm test the plug wires, check your plug gaps (if you didn't before reinstalling them after the swap) And I would hook a fuel pressure gauge up to it and see if your fuel pressure is good under WOT.