340 Static Compression Numbers and Test Procedure
I took some shots inside the cylinder. I did not see any numbers but the shape of the piston may be some of you can comment on.
Also when I had it in the shop we theorized that the timing was indeed off one tooth. I don't know how to read these markings but they reset it after this picture was taken and buttoned it up. I actually felt it ran better (like in the picture off by a tooth) before they moved the timing over one tooth (not pictured).
View attachment 1715455157
View attachment 1715455158
View attachment 1715455168
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.
