Community Shop Talk

Blow-by Solutions

| March 2005

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Online Engine Conversations 


• On my Jaeger, the cylinder was honed and the piston was put back in with the old rings (six of them), and the engine ran well after the rings took a seat. After a few months of running occasionally, there is a noticeable amount of blow-by. I see no reason for this to start now, any ideas why? What can I do? - Mac

• I have never had any luck reusing old piston rings. I know a lot of people that do it, though. If I don't have to pull the piston out of an engine, I don't. If I have to, I replace the rings. The rings are probably one of the cheapest parts you can buy for an engine. If I were you, I would get a new set of rings and lightly hone the cylinder to break the glaze, if there is any, since you said you honed it not too long ago. You should also check the side clearance of the rings in the grooves. If that is excessive, compression can leak around the back side of the rings. These are my experiences so take them for what they're worth. - Mike

• Every now and then the oiler will have air blow back. The piston is getting about 15 drops per minute and at 10 or so the bottom of the cylinder had no oil. Is too much oil possible, gumming up the rings? The engine never does any work because I have nothing for it to run. Oil is not blown off the rear of the piston in any great quantity, just a puff of exhaust from the top of the cylinder/piston when it fires. Any more information needed to evaluate the situation? - Mac

• When you honed the cylinder you forced the old rings to get about 20 years of accelerated wear in a day's time. By introducing this much wear, you most likely wore the rings much past the point of working "acceptably." Had you not honed, you probably could have gotten away with it. In any case, there has been a past compression problem with your engine.

"If you have good compression when turning it one way and much less when turning it the other way, I would expect to find excessive wear." 


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