I have a question on 502 mag rec. port heads is it true that you shouldn't replace valve seats in marine heads? I heard that they would most likely fall out sooner or later if replaced looking for some input thanks

Good question. Wheres all the machine shops??? I was also told that if the seats are bad, then the heads are junk.(marine application) Is this true? Can you replace the seats with a peice of mind that they wont fall out and ruin the engine?

yes you can replace the seats-just make sure it's done by
a shop that knows what their doing, and that it's a marine app.
aluminum heads are the ones that need close attn.

I think Teague had a write-up on this in powerboat a few months back.

Until I bought my latest project I would have said no problem as long as you have a good shop do the work. I am just finishing my HP450 that had the same problem. #4 cylinder dropped the exhaust valve seat, shattered it and beat the top of the piston up a little. I thought it would be an easy fix. Two new (complete) heads, one new piston-rod assy, one gen VI block, bearings, gaskets, machine work........etc. With me doing the assy work I'm in about $4000.00. Considering I got a good deal on the boat I'm still doing ok, BUT....when it's time to overhaul the other engine I will definately keep this in mind and spend the extra money on a new set of heads. It's cheaper in the long run.

I have replaced several of them in those heads and have never had an issue with them coming out later. You have to use the correct seat, and you have to machine the head for the proper interference fit. I know of a couple that have been running for a few years now and have not seen an issue at all.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md