Young Performance

Can you post a pic of the head gasket? Are you sure it was copper? I ask because that is the wrong head gasket to use, especially since the block is not o-ringed. Although pics can be deceiving, it certainly appears that it was leaking between the cylinders. You will definitely want to get a machinist straight edge on the deck and check for flatness between the cylinders. You will want to do the same with the head.
Eddie

GPM

And I thought you were kidding.

sutphen 30

what is the water pressure when your running hard?

Steve H

I had the same issue on a pair of 502s. The intake valves started leaking after about 25 or 30 hours. The "experts" kept telling me that I was running it lean. So I purchased Holley Hp EFI from Haxby Speed and Marine. Made darn sure the AFR was dead nuts. Then the intakes started to leak again!

I called Bob M. He asked me to send him high res pictures of the valves and seats. He concluded that the valves were floating because of weak spring pressure. By this time I was beyond frustrated, and ordered new AFR heads, lifters, and pushrods from Bob. He had the heads assembled to his specifications. I now have 150 hours on the clock with no issues. These engines are installed in a 42’ 16,000 pound boat, and are used very hard.

I’m not claiming to be an authority or expert of any kind. Just sharing a very similar experience, and how I got it resolved.