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  #1   IP: 174.125.117.120
Old 04-11-2019, 10:57 PM
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Red face #4 sticky valves, again.

OK, I know, I've been here before; some people never learn. Last couple years I was busy remodeling, then two grandsons born 2K mi. & 6K mi. away. So my 40 y.o. A4 reminds me about the true cost of neglect. Picture the corroded valve seats and ex.manifold, and its stud. New valves, keepers, washers and assorted gaskets should arrive from M.M. tomorrow. Question is, should I just 'lap the hell out of it' as my machinist neighbor said last go 'round? Or is it time to face the music, pull the engine, and have the machine shop regrind the seat in 'proper' fashion? And only two studs came free when I pulled the head; the corroded back manifold stud (top) did not. I'm inclined to give the in-the-boat DIY another go, but I'm open to suggestions from wiser folk than I. Thank you.
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  #2   IP: 108.60.227.10
Old 04-12-2019, 11:28 AM
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Can we see a shot of your exhaust system?

Given the amount of corrosion showing on that exhaust port, I would suspect you are having water or moisture intrusion into the manifold from the exhaust. This is a frequent cause of sticking valves.

A well designed exhaust should have the dry part go as high as possible (mine is 12"), and then inject the water at least 4" below the high point, but more is better.
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Last edited by edwardc; 04-14-2019 at 04:56 PM. Reason: Typo
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  #3   IP: 174.125.117.120
Old 04-12-2019, 12:20 PM
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Red face Exhaust riser

I think the corrosion is both external and internal, due to leaking heat exchanger and salt air via exhaust section.
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  #4   IP: 71.208.55.235
Old 04-12-2019, 01:56 PM
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Those seats sure look like they need to be recut. It could be done in the boat though.
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  #5   IP: 97.93.70.7
Old 04-12-2019, 04:36 PM
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That water injection point needs to be at least 3~4 inches further downstream.
You could plug it and add the MMI injection Tee below the end of the elbow.
Also check the manifold to see that it has no internal leaks as well.

Dave Neptune
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  #6   IP: 108.60.227.10
Old 04-12-2019, 05:56 PM
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Quote:
Originally Posted by Dave Neptune View Post
That water injection point needs to be at least 3~4 inches further downstream.
You could plug it and add the MMI injection Tee below the end of the elbow.
...
Dave Neptune
I agree. It looks like it's only about 1" below the bottom edge of the top of the loop. This allows splashing and steam to easily get back "over the top" and drip down to the manifold.
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