At the risk of show my ignorance / inexperience, what are we looking for with:
A) Compression testing? What should I theoretically expect to see and how do we correlate real world results to the expected value?
B) Leak down – measure of ring / valve seal efficiency only?
Compression test measures the ability of the engine to take in air and compress it.
Leak testing just checks the ability of the combustion chamber to hold air. Leak testing is also good to check for blown head gaskets and cracked heads, pressure the cylinder, take off the radiator cap and look for bubbles.
I also like to use a vacuum gauge when testing. Performance engines have low idle vacuum, but will still show 18 to 20 inches if held above the lope of the cam. Low vacuum means something is wrong, if the needle is bouncing while low its in the valve train, just one example.
