cylinder compression

[rupert's]

Good afternoon friends!
After a year of use with the Mutt, I have remeasured the compression on the cylinders, cylinder one is at 90 and the other three are at 95. If I put oil in the cylinders the compression goes up to 115 or 119 on all of them.
The solution is to change the cylinder rings and polish the valve seats, but... the engine runs fine and I don't know if it's worth it...

What compression should the engine have? and what minimum compression should it have?
In your opinion... is it worth going to all these troubles for a little more compression?
Thanks for your opinions! Greetings to all!

[rickf]

The compression should be around 115-120 with the lowest being no less than 10% different from the highest. BUT, if it is running to your satisfaction then leave it alone. When you did the compression test did you block the throttle in the wide open throttle position for the entire test? This is where it should be for a compression test and not doing so can give you the lower readings.

[Mr. Recovery]

I just looked it up in TM 9-2320-218-34 from Jan 1972 and it list the Cylinder compression at cranking speed as, 135 to 145 psi.

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[m3a1]

It's a MUTT....not a race car. If it gets you where you're going fairly reliably, I'd say leave it alone.

[rickf]

135-145 is pretty optimistic for a 70 year old engine! Especially one with 7.5:1 compression.

[rupert's]

Voucher! for now I'm going to leave it that way maybe, later on I'll encourage myself and get my hands on the engine, but for now the 145 compression will wait
Thank you all for your quick response!