239 Flathead No Compression
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New User
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239 Flathead No Compression
Hello, i have a 1953 mercury with a 239 flathead engine. I recently replaced all ignition components i.e : distributor, condenser, points, battery. Thinking since it wasn't seized and crank turned it had a chance to start. After verifying spark and timing with no luck i performed compression check of all cylinder. 10 psi on all. Are there any other checks before i pull the head to check the valve operation. Please Help
Welder User
Joined: Feb 2009
Posts: 5,269
Likes: 50
From: northwest MT
You might put a little oil in each cylinder and try it. I would pull the intake manifold first to make sure it's not full of mouse nest, etc in there. seen it happen.
You would also be able to see if the valves are moving as well.
You would also be able to see if the valves are moving as well.
Fleet Owner
Joined: Jul 2004
Posts: 27,298
Likes: 1,059
From: NM
Take out the plugs and look thru the holes while rotating the crank. You should be able to see the valves moving. If no movement, the timing gear may have failed. The stock gear is made of phenolic.
Cargo Master
Joined: Aug 2010
Posts: 2,927
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From: Houston
You can try a "wet" compression check. Squirt some oil down the cylinders and take the compression test again. If you numbers come up a lot then your rings are not sealing. If your numbers don't change then your valves are not sealing.
I'd recommend squiring a lot of automatic transmission fluid in the cylinders and at the valves. Let everything soak and see if your engine gets better.
How long has the motor been sitting? Was there a carburetor and air cleaner on the motor while it was sitting?
I agree with pulling the intake and investigating the timing gear too.
I'd recommend squiring a lot of automatic transmission fluid in the cylinders and at the valves. Let everything soak and see if your engine gets better.
How long has the motor been sitting? Was there a carburetor and air cleaner on the motor while it was sitting?
I agree with pulling the intake and investigating the timing gear too.
Fleet Mechanic
Joined: Dec 2005
Posts: 1,603
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10lbs on all, huh? I trust the check was done with wide open throttle. 10 lbs is
pretty uniform something fishy. I just think its improbable that all 16 valves are
leaking or all 8 piston rings are stuck? I would get any piston up, valves closed and
put shop air in there. So its either air escaping from tail pipe or carb. or out of
the oil filler pipe. oil pipe =rings tail pipe or carb. = valves.
pretty uniform something fishy. I just think its improbable that all 16 valves are
leaking or all 8 piston rings are stuck? I would get any piston up, valves closed and
put shop air in there. So its either air escaping from tail pipe or carb. or out of
the oil filler pipe. oil pipe =rings tail pipe or carb. = valves.
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