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I'm new to engine knocking so if I say something obvious or stupid just bear with me. I have a basically stock mark IV 427 with two bolt mains. It has recently developed an engine knock that only happens when it has reached full operation temperature (~180.) I had tried to pinpoint the source of the knock and it seems to coming from the bottom of the engine (or at least that is where it is the loudest, I was not able to trace it to a specific cylinder.) the knock is really loud at idle, but when I increase the engine speed from idle the knock actually goes away ( in other words it only knocks at idle.) At idle the engine has around 40 lbs. of oil pressure.

Thanks,
Bob.
 

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Hammer and a torch
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I agree pulling the pan would be first order... Also I would look close at the center 4 rods for issues or the very front main bearing...?
 

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I would pull the plug wires one at a time while its idleing. When you hit the one knocking it shoud stop or be reduced. That way when you look at the bottom end you will know where to start. I have a friend that had what seemed to be a bad rod knock and he drove that car for about 10 years like that. I wouldnt recomend that but his must have been a wrist pin. Thats the only thing I could think of for not blowing up for that long. So keep in mind if the bearings are perfect it could be a wrist pin.
 
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