Results of Compression test

Afordman31

Afordman31

Well-known member
I have a flathead that I took a compression test on, and these were the readings. Maybe someone could enlighten me as to my results. Is it a mixture of valves and rings or would the valves be the problem?
 

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I'm no flathead expert but those numbers look pretty low any way you look at them. Probably going to need the works.
 
Your readings are pretty low. Has this engine been run lately? If not I would get it runing and recheck the compression much later. It won't be perfect but may improve. Gary
 
The rise in the reading from dry to wet indicate leakage around the dry rings. As you can see, #1 and #2 as still very low wet. #1 I would think indicates a ring issue that is only partially helped by adding oil and #2 appears to have a problem other than rings that is accounting for the low reading. Was the testing done with the throttle blocked wide open?
 
Did you have a good battery that would spin the engine and did you run it at least three revolutions for each cylinder?
 
Often the reading will go up if the carb is held open. Like it says above, run the engine a while and run a test before it cools.
 
Throw some Marvel Mystery oil down the cylinders and let it set a few hours, then fire it up (if it runs) run it for about 20 minutes then do another compression check, sounds to me like rings are stuck.
 
we on the ford barn are assuming that you have removed all the plugs, blocked the throttle all the way open and have a good battery, even a 12 volt to give it a good spin. if this is the case pour some MMO down the cylinders and let it soak for awhile, then before you try a compression test again pour some motor oil in the cylinders and give it a try. blown headgaskets usually level out compression between two cylinders, burnt/stuck valve will yield near zero, and stuck/dry rings will yield low readings. just did a test as outlined above on a 40 and got 120 plus
 
Like said .... Get it running for a while to loosen it up. Longer the better. MMO it. Then get a vac gauge hooked up to it. Should normally be 19 to 21 but down to 17 might be ok for a driver. Most important watch vac level and especially needle movement - that's going to tell you a lot about your valve and internal conditions i.e. bad gaskets etc
 
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