Cylinder #7 (left, rearmost) is oil-fouling the sparkplug and burning oil / smoke from that side exhaust.

Heads received valve-job from a reputable machine-shop and New (IIRC) Viton Oil Seals,Valve-Springs, Retainers, 8-months earlier.

Figured it must be worn rings. Yesterday, compression check. The "Bad" #7 cylinder produced 143 PSI which is average to a bit higher (Entire Engine, Lowest = 137 PSI, Highest = 148 PSI.)

Squirting some oil into #7 cylinder and retesting compression, no change or increase.

So, could the oil-rings go bad, yet compression still be Ok? What is the likely problem? It Smokes and fouls that one plug only. Seems to run Ok.

Engine is an AMC V8, Factory Original engine, in a Jeep CJ5. Basically, a daily-driver with a moderate aftermarket cam, intake, ignition, headers, dual-exhaust, Holley 4BBL.

Is the valve-guide and / or valve seal more likely the problem?