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Discussion Starter · #1 ·
I'll be picking up a compression tester and a timming light. (tossed out two or three thinking I'd never need one!)
I have two engines I'd like to test. Both have set a long while.
I lube the sleeves and rings through the plug holes with a little oil so they are not bone dry.
I suppose if the valves are not set right it could make alot of difference.

The question is... Will lubing the sleeves and kicking over a relic engine give a reasonable indication of the condition its in?
 

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Sensei
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NOT Necessarily...here's why.....
The engine being cold will make it read lower than spec even if it is up to spec.....
Oil in the cylinder will effect a better seal, so it will read higher than it normally would under the (otherwise) same test conditions....Since you have NO way to determine what percentage of the relative increase (oil) and decrease (cold) actually are and from which, that test is meaningless.......
Filling the sump with clean oil to the proper level and running the test after several kick-throughs with the plugs out would at least yield a "cold test" result...... Remember, choke off and throttle wide open (or simply remove carbs)...Cold results tend to be 5 to 25 PSI lower than hot tests, but at least you'll have an idea the engine is probably OK if you have 150 to 155+ PSI....
Then add oil and repeat.....Signifgantly increased pressure usually indicates a ring problem, no signifigant change would indicate valve errors....
 

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Discussion Starter · #3 ·
Then add oil and repeat.....
I'm not following that part. I thought it had normal oil lever to test it?
or do you meen on a little on top of the piston?
 

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Discussion Starter · #5 ·
Okay, but could you explain why?
Is it because the oil is allowing the rings to "work" better by creating a seal?
 

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Sensei
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Yes.... A better ring to cylinder wall seal ..... If pressure rises drasticly, the previous test had a bad seal (weak or bad rings).... If pressures are low and the bit of oil on the rings doesn't help, the problem usually is in the valve to valve seat closure.....
 

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Discussion Starter · #7 ·
Thank you for that.

I have to think of what's really going on in there, then it starts to make sense!
 
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