I've just bought another miata (5th, 3rd turbo project) and have done a compression test. It goes as follows - 179, 181, 162, 215. The #4 high reading is most likely due to a leak in the valve colver gasket leak because there was a bunch of oil around the plug. Safe for 250hp with new head gasket and some head work? Should I replace the valve cover gasket and conduct a new compression test to be sure of #4s actual compression? Rebuild? Any expertise is greatly appreciated!

 

highly doubt a vc gasket will cause that high last number.

leakdown test that ****

 

Would that narrow it down to a bad ring?

 

there's only 3 possible outcomes: rings or valves.....or hg I guess

vc gasket has nothing to do with this. at all.
unless your spark plug is loose, and you somehow flooded the combustion chamber when testing it.

those numbers are not that good. I'd definitely do some more diagnosis before boosting it, unless you don't care, in which case boost it and just destroy it.

 

Okay, thanks!