If the head is warped it has to be machined or replaced because it won't hold compression when reinstalled. You use a feeler gauge and a straight edge in a cross corner to corner to check if clearance is in spec.
Looking for advice on an Atomic 4 repair / replacement
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Originally posted by joe_db View PostThe head has nothing to do with the valves sticking. I am not sure I get the connection
This started as a zero compression issue with the general consensus of the forum membership that sticky valves were the likely cause. We talked about how to turn the engine to find TDC in a Catalina 30 and I don't recall any resolution to that discussion. We talked about using a feeler gauge to measure for stuck valves, no resolution to that either and then the valves are on their way out of the block without a diagnostic measurement. Now the head is going to a shop for possible facing/milling? What happened to the stuck valve hypothesis? We don't even know for sure if that was the problem and it doesn't look like we ever will.
Sorry . . . .Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Originally posted by ndutton View PostI have to agree, this is hard to follow. We just jumped from valve keepers to head surfacing and it's not the first time. It seems we don't finish anything before jumping to something else.
This started as a zero compression issue with the general consensus of the forum membership that sticky valves were the likely cause. We talked about how to turn the engine to find TDC in a Catalina 30 and I don't recall any resolution to that discussion. We talked about using a feeler gauge to measure for stuck valves, no resolution to that either and then the valves are on their way out of the block without a diagnostic measurement. Now the head is going to a shop for possible facing/milling? What happened to the stuck valve hypothesis? We don't even know for sure if that was the problem and it doesn't look like we ever will.
Sorry . . . .
Check out the photo above. The valve seats are cooked. Destroyed. No valve clearance adjustment is going to make this engine run again.
Valve clearance is one of the last steps to a top end rebuild. You don't do that until after checking to make sure the valve seats, valves, springs, and etc are in good order...
As for manually turning over the engine.. there were 2 resolutions:
1. Yes you can put it in to gear and rotate the prop shaft.
2. You can cut an access hole to the flywheel and modify a socket to adapt. Or buy the official tool from MM.
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All true, but an A4 does not have a "top end" like a car, the valve seats are in the block. If you have the head off anyway by all means have it checked for being warped, but that is a totally different issue.Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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Thought I'd give anyone following a bit of an update. I called around to 5 or 6 machine shops. Almost nobody has the equipment to machine valve seats on a flat head engine anymore. Everyone has moved on to machining valves on heads. I did get referrals to shops who could potentially do it, but they all refused the work.
They said that from their past experiences, they are highly likely to strike water due to water jacket and other corrosion.
But yes, this block can in theory be machined by drilling out and installing new valve seats.Last edited by infy; 05-20-2019, 01:21 PM.
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Wow, I stand corrected on the valve seats. What a weird bit of corrosion. It looks like rust, but wrong color. Was there any acidic rust stabilizer used in cleaning this?
Its disappointing that you can't get a machine shop to help. The equipment for grinding seats on side-valve engines is the same as overhead valves. The A-4 is particularly easy to do, just lift it up on the bench and have at.sigpic Whiskeyjack a '68 Columbia 36 rebuilt A-4 with 2:1
"Since when is napping doing nothing?"
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Originally posted by lat 64 View PostWow, I stand corrected on the valve seats. What a weird bit of corrosion. It looks like rust, but wrong color. Was there any acidic rust stabilizer used in cleaning this?
Its disappointing that you can't get a machine shop to help. The equipment for grinding seats on side-valve engines is the same as overhead valves. The A-4 is particularly easy to do, just lift it up on the bench and have at.
Best guess is this engine was probably run for a long time on bad/wrong spark plugs or with carbon deposits. Damaged by detonation/pinging.
Change your spark plugs people make sure they're to spec.
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