Misfire at cruise, popping/afterfire at 3000RPM

I have never known what cam I have. Previous owner didn't have any documentation on the engine build, so when I sent the heads off to the machine shop, I measured lift. It was something like .447 on both intake and exhaust -- it's written down somewhere -- so they did their best to match the springs to that. I'll try to dig up the spring p/n, but the pressures they gave me were 120 seat and 285 open. I know that probably doesn't help without knowing the spring part numbers.

One thing I didn't do once the heads were back and installed was to perform another leakdown. I need to do that.


I know you've mentioned reversed polarity before, and I've tried to pay attention to the light while checking timing. The light seems pretty consistent until it gets to the higher RPM, and then it will skip around a little in position, maybe miss a strobe here or there.

My question is, how would polarity become reversed? New distributor, I've tried 2 additional harnesses for a total of 3. Are you referring to having the coil wired backwards? Initially I thought you were referring to the distributor pickup wires, but how would I end up with 3 harnesses and 2 distributors, all with incorrect polarity?

Assuming HYD cam 'though those pressures will run about a .500 lift solid according to mopar" Are your pushrods arent too long?
Measure preload.
Check pushrod length. Do the math, check all 4 corners 1, 2, 7, 8
You can cheaply buy some rocker shaft shims from Mancini racing. Assuming the valvetrain isn't adjustable the idea is to raise the rocker arm off off the pushrod and give up some preload ..the effect is like shortening the pushrods. I believe the shim kit has .030 and or .025 varieties.
Or measure and if so.. buy new push rods.

IF that's even your problem.
Long distance diagnosis can be a crap shoot.