twohandstech

Here are the basics, please help if you can:
91 5.0/302 Roller HO in a Carburated 67 mustang

Ran fine for about 20 minutes on the way to the DMV, then all of a sudden is sounded garbled on one side and would not idle. I cranked down the idle screw just to get it to run at about 1100 rpm. When driving, it would lurch a little at times, and I had to put in Neutral at stop lights to give it gas until I was able to get it back home.

There is a definite ticking noise coming from either: valve cover, or I may have not tightened down the exhaust manifold well enough, and there is an exhaust leak. Not sure which it is.

Did a compression check on that side, and all four cylinders are at 120psi.

After the engine is hot, I put a piece of plastic on each of the exhaust pipes. #5 and #8 melted it immediately, while 6 & 7 were warm, but did nothing to the plastic.

Removing #6 & #7 spark wires also causes no change, which is why I believe 6 & 7 are misfiring.

I've got good spark. The number 6 plug was black and a little moist, so I put in a new one, but still having same issue.

I'm not sure how to verify that #6 and #7 are getting fuel, which is the last item to verify.

Is it possible that this is a bad head gasket, or valve seal, even though I'm getting good compression? Or maybe the lifter is loose, and the intake valve is not opening to allow fuel?

Your thoughts are great appreciated!