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Posted By Discussion Topic: stuck valve -- page: 1 2     stevep 10-23-2009 @ 4:04 PM reply profile send p.m. Member Posts: 8 Joined: Oct 2009 I think I have a stuck valve. The engine is making a tapping sound, backfired thru exhaust once and idles rough. I started the car in my garage and after about 3 minutes the tapping sound started. Does anyone have an easy fix for this problem? tierod 10-23-2009 @ 6:10 PM reply profile send p.m. Member Posts: 73 Joined: Oct 2009 If it is a hung up valve what has worked for me is a dose of Marvel Mystery Oil down the carb with engine running. Good luck. 51f1 10-24-2009 @ 5:16 AM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 Many years ago, I freed up a valve in a Navy surplus (WW II) Kohler engine with Marvel Mystery Oil. The engine had been in storage for 20 years. I probably added it to the gasoline. Marvel Mystery Oil is one of the old wives tales that actually works. Richard This message was edited by 51f1 on 10-29-09 @ 5:44 PM TomO 10-24-2009 @ 8:50 AM reply profile send p.m. Senior Posts: 7250 Joined: Oct 2009 MMO is the answer. Pour some down the carburetor and smoke up the neighborhood. The add 1 quart to the oil and drive the car about 50 miles. Drain the oil and refill it with fresh oil. Then add some MMO to your gas for a few tankfuls. Some people add it to every tankful. Tom supereal 10-24-2009 @ 10:05 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 I'd run a compression test to see what is happening. While a stuck valve isn't completely rare, it can be from another cause, and running the engine can cause a lot of damage. About a month ago, a customer brought in an 8BA engine to be rebuilt. We found that a valve seat had come loose and broke, with the pieces dropped into the cylinder. It battered the piston and ruined the cylinder wall. We may be able to sleeve it and save the block, but time will tell. We occasionally find that a valve seat has been "staked" into place after the pocket was made too large. With good flathead blocks bringing big bucks, it is worth determining which cylinder is at fault, and pulling the head to inspect the cause. It could be a broken valve spring or other problem, too. 37RAGTOPMAN 10-24-2009 @ 4:12 PM reply profile send p.m. Senior Posts: 1958 Joined: Oct 2009 HI pull the spark plug in that cylinder, see if you can look in the cylinder and see if both valves are going up and down, if it looks like only one valve is going up and down, try pushing down on the valve that is not moving,have a helper crank the engine by hand,using a starter crank wrench, also us a good grade of rust buster, like PB BLASTER cheap penterating lubes usually are not that good, this should free up the valves, put plug back in when you have compression back in that cylinder, removing all the spark plugs make it easier to turn the engine over. and a little top oil [ MARVEL MYSTERY OIL ] will keep this from happening, is car stored in a damp place ? LETS HEAR HOW YOU MADE OUT,!!!!!!! hope this helps 37RAGTOPMAN supereal 10-26-2009 @ 9:27 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Marvel Mystery Oil (MMO) is often recommended both as a preventative and as a cure. Just be aware that if overused, it can, and will, foul spark plugs. stevep 10-29-2009 @ 10:12 AM reply profile send p.m. Member Posts: 8 Joined: Oct 2009 Still having problem. I tried everything suggested but no luck. I have no compression on number four cylinder, but the exhaust valve is moving up and down what appears to be full length of travel. I can't see the intake valve. I think the only thing left to do is pull the head and intake. Anyone got a better idea? 37RAGTOPMAN 10-29-2009 @ 4:52 PM reply profile send p.m. Senior Posts: 1958 Joined: Oct 2009 HI STEVE if you had a old spark plug and a air hose connector you could make a leak down tester, by taking the spark plug apart and welding the air line connector,together, know you can screw the adapter into the cylinder,and using the air regulator, starting with low pressure start letting the air into the cylinder, be sure to put at top dead center, and lock the engine, either by putting into gear, jack up one rear wheel, now if it leaks into the radiator the head casket could be bad, if it leak out the exhaust, the exhaust valve is leaking, or a broken valve spring, if it leak up into the carb it could be the exhaust valve or bad valve spring could be broken, or in extreme cases it could be a problem with the vaalve seats, especially if some engine work was done, do some more checking and let hear how you made out, together with some help from others ,I am sure you can get in back on the road hope this helps 37RAGTOPMAN supereal 10-30-2009 @ 6:36 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 To construct a useful leak down tool, you will need to have a valve and a gauge. The valve isolates the air supply, and the gauge allows you to see how rapidly the pressure declines. The tricky part is being sure that the cylinder under inspection is truly at the top of the compression stroke. In the case of a large loss of compression, there is no practical substitute for pulling the head and intake to see what is happening, as correction will require it to be done, anyway. Large compression loss can indicate internal damage that may ruin the engine if left uncorrected. We have an 8BA engine in our shop currently that lost compression on one cylinder because the valve seat came loose. Continued operation caused the seat to shatter and heavily damaged the piston and cylinder wall. We hope to save the block, but it will not be cheap.

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