340 Static Compression Numbers and Test Procedure

Ignore the dots. You MUST degree a cam to know where it is.

Like I posted above, pull the drivers side valve cover, roll the engine to TDC number 1 cylinder on crossover (overlap) and LOOK at the rocker arms.

If the intake rocker is further open, the cam is advanced. If the exhaust rocker is further open, the cam is retarded. If both rockers are open the same amount, the cam is in straight up.

How far advanced or retarded the cam is can only be known by degreeing the cam.

That piston is a claimed 12.5:1 but you have to be about 64 cc's on the combustion chamber and the piston is out of the bore at least .020 or more, depending on the head gasket thickness.

I'm betting unless the heads have been milled to hell and the block decked a ton, you're probably at a true 10.5-10.8:1 range and that thing should be able to run full timing on 91 pump premium with no issues.

I doubt you'll be able to run a vacuum advance with that, unless you run it off of manifold vacuum and curve the distributor for that.

The real issue is even with manifold vacuum the mechanism works way too slow to pull timing back out and you get tip in rattle.
Great information YR! Thank you! I will try what you suggest WRT looking at the rockers as soon as I can.