Knocking after rebuild

[DBRYCHRIS]

Hey guys, looking for a little help. This is my first post here and this forum has been very helpful in putting my z back together. I have a 90 300z tt i just rebuilt the engine after having spun the #4 rod bearing, had the crank turned 10/10 used ACR bearings had the blocked cleaned and honed, replaced the rings and had the heads redone, new oil pump and gasket kit. during reassemble i measured everything,mains,rods and rings. i have rebuilt many engines and am very thorough. The rods and mains measured .0022/.0023 across the board and i was very happy with that, I got it all together and ran the engine for 30 minutes with no noise and 30 lbs of oil pressure at idle and 60 lbs above idle and than changed the oil and filter. I drove the car all around the next two days putting 130 miles on it with no problems, than I started to hear a little tapping sound that sounded like a lifter I didn't worry about it just figured it was the vct. I drove later on getting on it a little but not above 4500 rpms and started hearing the noise alot louder but this time it sounded alot deeper just like before. Now it knocks at idle and all rpms a very deep knock and my oil pressure is dropping o zero at idle. My question is why would have spun a bearing already, is their something i missed during the rebuild that should have been done on z engines that would be any different from a typical Chevy/Ford engine. One more thing that bothers me is when i got the car it was apart so i completely repainted and did a few upgrades including a intercooler and exhaust and rebuilt the turbos ( which the driver side is already smoking) but did not rebuild the engine just resealed it. Once i got the car running for the first time it ran great and right around the same miles (140) it started knocking and oil pressure dropped to zero at idle. So wtf i don't understand how i could have spun two rod bearings in the same amount of time unless I'm missing something. I would appreciate any input as I'm about to pull the engine and see exactly what failed.

[awesomekasim]

no motor rebuild experience here but it seems you know where to go from here. Tear it all back down and see what failed

[DBRYCHRIS]

Yep, that's the plan this weekend. I will post an update once available.

[es.biggs]

Anything can happen man, sounds like bad luck. You know what a spun bearing sounds like...let us know how the weekend goes.

Just goes to show some things don't go as planned even when you least expect it. Sorry to hear man - I've been in a similar situation before.

To answer your question though, I can't think of anything special about this engine and the way it's assembled.