During tear down of my 502s, I found that ports 7 and 8 have shown so evidence of water being in the port. I’ve already pressured tested both sets of headers and none are leaking. I had no evidence of water in the oil so perhaps it was minor. Still, I think I lost an exhaust seat on one of my heads suspecting water behind the seat as the cause. I store the boat on the trailer tilted pretty high up. Could condensation and the degree of tilt be causing this?

Adding, I pressure tested at 40 psi using a tub and then moved them out of the tub and applied heat with no change in pressures.

And because I wanted be as thorough as possible, I decided to repeat the test (just air) using a propane torch to really heat it up. I just finished the starboard headers. Pressure increased about five pounds with heat so I think I have a valid test. No losses.

088 heads? Reason for asking is a few years back on my Sonic I was chasing my tail and the machine shop pressure tested the heads and found leak to be tiny rot in exhaust valve port. Was told this a common issue. Good luck.

Yeah, 088’s. Replacing with AFRs so not really an issue there.

gm heads have water surrounding the exhaust valve guide,I have seen them rot in that area

Got it. But happening on all four heads? The head that appears to have lost the seat was refreshed last season.

Is there a best practice for dealing with condensation? One thing I’ll be doing when the engines go back in will be the addition of drains that will let the water run out of transom dumps at shutdown. This would eliminate cold water after flushing and I’m thinking that could cut down on condensation.

I don’t want this being an issue going forward.

as sutphen mentioned...could be rotted valve guides. if that were the case, I’d suspect you’d see it on more than two cylinders. just my opinion.

what cam are you running...given it’s cylinders 7 & 8 my guess is you have a small case of reversion. assuming it’s wet exhaust?

I’m going to pull the valve on the head that had what appears to be a seat issue.

These are 502 MPIs, 1998s with maybe 200 hours on one set of heads and less that 20 on the other set.

it’s possible there was some reversion on the port engine because the flat gasket on one tail pipe (CMI Etops to TRS tails) looked like some gases were getting by. The starboard side was sealed up tight but had the same damage.

I’ll get some pics of the heads here shortly.

Tom, I had some loose header bolts that I believe caused a similar condition in the exhaust ports on a couple cylinders years ago. Any carbon trails on your gaskets or headers around 7 and 8?