help

Like gouges but cant tell. Got a fellow A'r coming tomorrow. And going to bring a little scope cam to see down in it and get a plan of attack.
 
You really need to remove the valve cover to check the valves. You can tell if the valve is stuck open on the number three cylinder. With the spark plugs removed the engine will be easy to turn with the hand crank or the starter. With a helper turning the engine watch the lifters where they meet the valve stims on the number three. If a valve is stuck open you will see that one of the valve springs won't be moving. I would be positive that a valve was stuck in the up position before pushing on it with anything. If you don't want to lose any oil, you can drain the oil pan first and if you don't want to change it you can replace it..

My first guess for loss or sudden loss of compression would be a stuck valve. With ethanol fuel, it can happen pretty quick, its happened to me. Still doesn't explain knocking and loss of oil pressure.
 
1930 coupe said:
This is way out in left field and very remote.
What if a small rock or something bounced up from the tire and got sucked in the carb and made it to #3 cylinder. Could make a knock, scar up the piston and hold the valve open.
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It might be possible, but I'm pretty sure he is running an air maze.
 
It could do all of that if a rock was in the cylinder. The engine wouldn't have enough vacume to draw a rock through the carburetor ,up the manifold and enter the combustion chamber.
 
One guy lost a carb jet tube & it sucked it in & it stuck under a valve. Bill W. (Just pop off the carb bowl & see if a jet tube is missing)
 
Well we took a look with the camera and didn't see much so going to pull the head and take a look. Leaning toward a bad exhaust valve.
 
Good move report results
Also take off the radiator cap and make sure no air is coming up through the cooling system along with checking at the carb throttle plate open and tailpipe, // crankcase oil fill...
 
Good call, Bill. But how can you lose a valve seat? It's smaller than the head of a valve, so it wouldn't come off and over the valve, and too large to get into the block. Wouldn't it just rattle around in place? Am I misunderstanding something?
 
700rpm said:
Good call, Bill. But how can you lose a valve seat? It's smaller than the head of a valve, so it wouldn't come off and over the valve, and too large to get into the block. Wouldn't it just rattle around in place? Am I misunderstanding something?
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I'm guessing it shattered. The seat is gone and there was no pieces anywhere.
 
bhiland said:
I'm guessing it shattered. The seat is gone and there was no pieces anywhere.
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I would imagine that a complete loose seat could hang out over the bore & be clobbered by the piston & the pieces passed out the exhaust valve & are probably rattling happily in the muffelator. Possibly piston damage, also. Bill W.
 
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