5.7 Rod bearing

[Durfman77]

Hello, well I got 94 GMC with 5.7 and only 155,000 miles,,truck is like brand new,,I change oil every 3000 miles,only use good synthetic oil. Let it warm up in winter,, I take good care of my truck. Other day heard noise???? Stopped open hood sounded like someone in engine with big hammer. I dont understand why this happend? Any ideas??
Got a 4 bolt main with roller cam going in it now with long tube headers,, should be good to go??

 

[Cousin_Eddie]

My son's 89 has the same issue I think. His doesn't make noise until it warms up. Then you start hearing a knock. When I researched the issue it came up as a wrist pin knock and it's apparently pretty common. The general consensus is that it's not going to blow up anytime soon and many have just ignored it and kept driving without any issues. We are going to rebuild my son's because a knock in the engine "just ain't right". It drives me nuts when we fire it up to move it every once in a while. It will get attention once I'm done with my 84.

 

[Blue Ox]

GM had a problem with excess timing advance on cold starts. Sorry, I don't remember which years, but it was in the GMT-400 era. The timing would immediately go to maximum, like 40° on cold start. Oil pressure ? We don't need no stinkin' oil pressure. They destroyed a lot of rod bearings that way. I don't think they ever had a reflash for it. Just a service bulletin about playing mix-n-match with undersize bearings to close up the clearances.

 

[Durfman77]

Im not sure yet? My truck too would not make any knocking noise untill warmed up, then sound like someone with big hammer inside motor,lol.. There pulling motor this week should have truck back by weekend. I would have did it but had 2 surgeries on my hand, repaired tore tendons.