So I bought this 502 mag from a guy in NJ. Seemed like a nice guy to do business with. The engine I bought sat for a year. Once it got here to Texas I installed in my velocity 280 and it still had oil in it from when it was in his boat. I bought this engine as it had low oil pressure, turns out its the sending unit. So I fired up engine and it ran perfect. No miss what so ever, idled up nice and ran well. (Last year) So I never got a chance to take her out last year and she just sat in my back yard. I had some interior work done, (boat hatch) took almost a year.. so that whole time I had a tarp over engine in boat and it has rained like crazy here in Texas. Well a few weeks ago I got the rear engine hatch back and decided it was time to freshen up the oil and put AC1s in it. Fired boat up and it had a ticking noise coming from Port valve cover, ran it for a minute tops to see if it was just oiling issue and the ticking was so faint it didn't go away. I jumped out of boat and noticed the starboard side of boat had twice as much exhaust coming out. Immediately shut off 502, pulled exhaust apart on port side and noticed water puddles in bottom of manifold. I got it the rest of the way off and found that the back 3 ports were rusted so bad. Moving forward I pulled VC off and found an intake rocker loose. Pulled it off and it's a bent push rod. Pulled plugs from all the way around, spun engine over it all looked fine. Pulled an intake pushrod from another cylinder, put it in and it was loose. Spun it over and it bent the pushrod instantly. So I came to the conclusion the valve was stuck. Rusted stuck. Pulled upper intake off and found oil around all the runners on the lower intake and the upper had oil and water mix in it. Went ahead and pulled lower off and found the tray under lower intake had surface rust on it. Pulled starboard exhaust manifold and some of the cylinders had like stalagmites growing in them. I'll have the cylinder heads off in a few hours, and I'll be taking them to a local engineer that ports and designs heads. He said that we can port them and clean up all the rust, install larger valves I believe stainless steel and that should remedy the heads problem. This engine was a ocean engine and now is lake only. When I get head off port side hopefully I don't find a hole in the piston. It seems from reading different post on this site really none of my symptoms are uncommon on engines that have been in Ocean and set up for a year or two. Any thoughts or advice would greatly be appreciated. I'm poor and just wanna be in the lake this summer. Not ragging on my boat just putting around so I can drink cold beers with the ladies. I hope there is a Lil light at the end of this tunnel, thanks in advance God bless

If all is OK I plan to install heads back on with ARP studs, was unsure of head gaskets to use. I need to pushrods and evidently one of my injectors broke in the process..

It sounds like those heads are probably very corroded. I would be leary of sinking money into a head, that could be paper thin from salt rot. On something like that, I think I would be tearing the whole engine down and going thru it. If it hydrolocked enough to bend a pushrod , you may want to take a close look at the connecting rod as well.

How did you determine the low oil psi, was a bad sending unit, and not in fact, actually low oil psi?

It didn't hydrolock, the valve was rusted open and stuck.
Oil sending, checked with mechanical gauge

Did u get the oil good and hot and see what the pressure is at low idle? I had an engine that had 60lbs cold oil psi, and after a run, i would have 5-10lbs at idle. Turned out the main bearings were toast .

I let it run for about 15 mins. Never got hot, but the oil pressure went from about 45 psi to 30 psi at idle

If you have the GM "retrofit" roller cam pushrods (intakes are shorter by about 1") I have a set that you can have for the price of shipping, but it sounds like you may be deeper than that anyways.

I have 088 heads from 95 502 fresh from machine shop. Ferrea super alloy exhaust valves, stock stainless intakes. Brand new springs. Surfaced, valve job. Ready to bolt on.