Help figuring out miss in an HEI 350?

[ihv800]

Hello!

Working on an '82 GMC for a friend trying to get it tuned up and running nice. It was brought to me with a no start condition, an HEI module fixed that up. I used an NOS US made Echlin.

I've got a miss I cannot figure out, though. Cylinders 8 and 5. 8 seems to not be contributing at all. With no load 5 is dead, if you let it load up against the converter pulling the wire on and off 5 does make a detectable difference but it's a weak contribution.

Compression on 5 and 8 is around 130 as are other cylinders that are working fine. Valves are goin up and down so the cam isn't flat, and I have checked and readjusted the rocker arms. I've tried swapping plugs and wires around with good cylinders and the problem persists. I've tried new plugs and wires with no change. I've reclocked the distributor and moved the wires over one post on the cap, 5 and 8 still do the same thing. The spark will jump all over from the cap when you pull those wires off and have good spark at the plug.

I must be missing something but I've tried everything I can think of? I thought the pickup was doing something wonky, but figured reclocking the distributor would move the issue and it didn't. I don't see any ignition issues and it makes effortless compression when testing those cylinders. It is interesting to me that the problem cylinders are 180 apart. Before I pull the rest of my hair out I thought I'd put around the table for ideas.

Thanks!