Chevy bb 496
 

Hi Guys, New to the site! I am looking for some input on a 496 Chevy bb that I am running in a 23 ft Scarab concept. Was checking static cyl pressure the other day and was in the 140 psi range on all but @ 5 cyl and 6. they were at 90 psi. The motor had stock peanut heads ( i know, what was I thinking). I pulled the old heads today to install a set of 502 rectangular heads with a rpm air gap intake. I found a bit of moisture in the cyl with low psi. The boat was running good (60mph @ 4600rpm) Found a small crack on the right side head (#6 cyl) in combustion chamber. Im thinking I should bolt on the new heads and see how it runs.... What do you guys think?

Check the cylinder walls for scuffing. Pistons could
have some stuck rings from being overheated and partial seizure. Don't ask me how I know. Maybe why the head is cracked, too. Compression test indicates a tired engine. You should have at least 150 psi on all cylinders if healthy. You might try a different compression tester to be sure. Good luck.

Thanks for the input. Had a bit of scuffing on the cyl walls. I am pulling the motor tomorrow and going to do a quick hone/ring replacement and inspection on the bearings. Figured I would go up in cam size a bit while I'm at it. Keeping my fingers crossed!