Originally Posted by F-BIRD'88
You are likely hearing it leak past the piston rings. If the cranking compression is 150 its good.
On a stock OEM cam the intake is not fully closed until 40deg ABDC +/- The piston is approx 1/3 past BDC
The bigger the cam the later the intake closes (generally)
Did you verify accurate timing tab TDC location, using a piston stop to find true TDC?
often a issue with non stock aftermarket parts. inaccurate timing setting is the result.
It is a stock cam from the crate motor short block.