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What should the compression be on a '40 110?

Also, I think I have an exhaust leak. I am getting a pop pop sound that I didn't have before. If I lean over with a long screwdriver and try to listen to the engine it doesn't seem to be inside the engine itself. Any hints on trying to track it down exactly?

Compression ratios for the 1941 Six were 6.39 std and 6.71 optional and I'd guess that 1940 was about the same, so I'd think compression readings of about 90-95 psi should be expected.

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John,

Sorry to hear about your problem. Don't know that I can help on the diagnosis but give me a yell if you want a hand with anything!

Thanks all.........I'm getting 75lbs. At least they are all about the same.

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John,

Have you spoken to Peter about these matters? He might be able to offer some insight or advice.

Not yet...I am seeing him in a couple of weeks. Will ask then if I haven't sorted it by then.

I assume you took the compression with all the plugs removed and the choke valve held open? And did you do it "dry"? If so, I'd add a tablespoon or so of oil into each spark plug hole, crank the engine over several times, and then take it again. If the readings increase significantly it indicates ring and/or cylinder bore wear, if they don't it indicates leakage at the valves which is far easier to deal with. L-head engines of this vintage typically need a valve grind every 30,000 - 50,000 miles, sometimes more frequently if driven consistently at higher speeds.

My 38 110 ran very smooth but had low power and a hard hot start issue.Compression was @70 to 75 psi cold.After adjusting the valves -power was much improved and the hard stating was a thing of the past.
The service manual says to set the valves with the engine running and warm to .05 int and .010 exh.I found this almost impossible with the exhaust manifold hot and in the way of the center cylinders.Now I found out you can set them cold to .07 int and .09 exh.Removing the spark plugs, right front wheel and inner fender is a must.I didn't run a second comp test,hind sight indicates I should have.
RT

I hope you mean .005, .007 etc., not .05, .07 etc. Yeah, setting valves with a hot running engine is no fun at all! But if you can tolerate it, it gives excellent results.

No the choke wasn't open. I drove it till it was warm and then took out the coil wire....then I took out one plug at a time and then plug back in and off to the next plug. Why would one take them out all at once? Very shade tree here.