I have Tom Ward’s old pocket books, and in one of them he lists compression test results, which are VERY variable. From those lists, I would say that 90 to 95 psi is acceptable, if a little on the low side for a late Shipley engine. Some engines gave results as high as 140 psi, but were also listed as having serious detonation problems that were not remedied by retarding the ignition. He had to fit decompression plates to these engines in order to stop the detonation/pinking. One can only wonder WHY some engines were like that, and also wonder if that is how they left the factory, or a consequence of owners’ attempts at tuning.