Ok, I just got my engine put back together. It blew a head gasket about a month ago. So I decided I would do some work on it while it was apart. I put a ZZ4 cam in it, 3 angle valve job, headers, new timing set, and underdrive pulleys. I cranked it up and it ran perfect. Then when it warmed up it started making a knocking noise like the rod was knocking, but if it was a rod it should be knocking all the time not just when it gets warm, right? Anyone have any ideas as to what it could be? Oh it is a 5.7L TPI engine and I tried retightening the valves up that did not help. Any help would be much appreciated, thanks.

 

How's your oil pressure?

 

check oil pressure and make sure it's comming from the oil pan. for $hits and giggles check your flexplate. i recently bought my 86 TA for $600 due to a rod that only "knocked at idle when warm" . it was the flexplate. if you backfired , or the motor seemed to kind of kick back when you tried to fire it up , or when you blew the head gasket, it might have cracked the flexplate. not fun but much better (and cheaper) than a rod . if you rev the motor and it goes away or it goes away when your driving, and/or it's not a rythmic knock it's the flexplate.