I would JB weld the corroded pits on head and manifold surfaces and sand back flat. then I would buy a pair of heat exchangers and STOP ELECTROPLATING THE OCEAN WITH YOUR ENGINE!!! cmon people...2 grand for a bare 502 block. 800 minimum per aluminum head. and if the aluminum heads are as thin as the iron heads where the valve guides are, they may be rotted through and 50 cents a pound. I'm running a junk smallblock with Dart iron heads this year and I'm gonna run antifreeze in it.

you talk a lot of chit around here latley,what engine did i build thet hydrolocked?none but you try to stir up chit.haxby was right about you,just an internet troll!you have some serious issues.

jb weld will not hold up,the parts will need to be welded and remachined.i agree about runing heat exchanger in salt water.

Plus one on this - there is a reason that Merc went with closed cooling on their newer generation of engines.

Nordic95 Do you have an update status as of yet?

Did you check the exhaust as well?

So I pressured test exhaust header. 15 psi of air for two hours. It held fine. Then I went to pressure test block and instant air out the #8 spark plug hole. So I guess I know what I'm doing this weekend.

Sorry to hear that, but back to your original post you asked about the headgaskets, and yes if you have one bad replace the other, also inspect the head and block for cracks. don't assume anything, now is the time for a total and comprehensive inspection. Details, details, details. Good luck and lets us know what you find.