Engine know when hot and driving
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Teching In
Joined: Sep 2023
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Engine know when hot and driving I have a l76 stroked to a 403ci with a 6l80 behind it. After I had it dyno tuned it developed a know when driving and hot. It goes away after a couple minutes at idle then it will come back once I am driving again but not straight away. I have dropped the oil and the oil is sparkly with metal. Thought it could be a lifter or a trunnion bearing but I have changed them out since. Just need some more ideas on what to check before I pull the engine again.
Joined: Apr 2006
Posts: 3,931
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From: Grand Rapids, Michigan
Did you mean an engine knock? If that's the case, you can determine what area the sound is coming from by using a mechanic's stethoscope, available at any Harbor Freight. Otherwise you're just guessing, regardless of what anyone might suggest you look at. When you drained the oil, was it the first oil change after being built? You'll see some material in there if it was. If not, you can cut your oil filter open on the next change and look to see if there's more material in there. As for the sound of the knock, is it a low thud or is it higher pitched? A rod knock will be low in tone and a higher frequency than a valvetrain "knock", as the cam rotates half the speed of the crank.
