BadDog

What about using a bore scope and a dial indicator and comaring to a known engine?

baronbob

I am not an expert but I have melted down one supercharged motor and have it back working well (I guess you can call that experience). I also have an engineering background and therefore know where you are going with the correlation idea. There might be a correlation but that is not all you need. Cam profile, valve size, ring condition and many other factors effect dynamic compression downwards and could miss-lead you into thinking you have a blower ready setup. Here is an idea. It is summer and you may want to try the blower now so do it regardless of what your internals are. What you care about is detonation. Turn your full advance down below 30deg. If you decide to add timing you will find out what you don’t have. Run your set up and plan to do a thorough tear down this winter because you need to know about your cam, pistons, and you should have enduring exhaust valves. If you want to do it correct now then it will take a complete tear down to make sure the set up can endure the hundreds of HP you will be adding.

stevesxm

my feeling is simply this....

you KNOW for a blower motor that you need a much lower static compression ratio.

you KNOW this motor was NOT built with a blower in mind... so it , with almost 100 % certainty , was built with a compression
ratio for a normally aspirated motor... 8.5 or more.

you CAN look in the spark plug hole and see what the pistons look like.

i think you can safely assume that you COULD put a blower on without checking but it would be a VERY substantial risk. or you just run very low boost...

a smarter play would be to yank a cylinder head. then you know the answer and have a wide variety of options from running a thick head gasket to opening up the chambers etc etc etc etc .

having said all this i would still suggest that the cranking compression numbers are meaningless for what you are trying to feel better about.