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engine knock questions.


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ok a buddy of mine blew an engine on my friends dyno a couple of weeks ago. once the engine was torn down one of the pistons look like it had a hole burned threw the side of the piston. the ring lands were broke pretty bad and the top edge of the piston above the hole looked like it was sandblasted. here's my question. on the dyno we never heard any audible knock. A/F ratio was 12 and below booste was 18 psi. timeing was set basically like mine was and pulled about the same amount of time as booste rose for a total timing of about 20-22. it put down 275 the first run and as we leaned it out towards A/F of 12 about the 5th run the motor popped and set oil out every hole it could. was this motor hurt allready or is there a possibility it was hurt on the dyno. what are the chances of the engine leaning out... knocking and creating enough heat to do that without hearing something weird? or seeing something in the af ratio to indicate something was wrong?i think the motor was hurt before and possibly lean in that one cylinder maybe a bad injector???/ inputs????

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