This past weekend I pulled the 6G72 out of my 91 Monty to either rebuild or replace it. I've been driving it as is with 1 1/2 dead holes. My wife and daughter really liked riding in it since it had head and leg room that puts our Saturn to shame. The Monty has 224k miles on it and so far since getting it I've replaced the rear brakes, the idler arm, shimmed the rear control arm bushings, lubed all electric door locks and windows, and spiffed up the interior.
I decided to pull the engine after the startup rod or main bearing knock would last longer every time it was started. Once I got it out and torn down, I found the oil pickup screen plugged with sludge and particulate. There was a pile of it in the pan and the valve covers were also sludged to the point of plugging the PCV valve and port. The rod and main bearings were worn down to the copper, but the crank was standard journal size. The block had been rebored to .50mm oversize, so somebody rebuilt this engine at one time. They used Clevite 77 bearings on the rebuild. I wish they would have maintained what they had!
I haven't pulled the heads apart yet, but it's interesting that the one obviously burnt valve is a different make than all the others. They had a letter on the valve head and the burnt one was plain. My plan is to get the crank miked and see if it needs a grind, get a set of rings, valve job, oil pump, timing set, valve dampeners, injectors, rod and main bearings and a rear seal. It has an auto trans so I'm thinking a rebuilt converter and front trans seal also.
A local guy was selling a JDM 6G72 engine that he bought to put in a Dodge, but he didn't realize it wasn't a bolt in. I was going to go that direction and install a low miles engine. I think I can rebuild this one for less. First chore is to take the pan and valve covers and have them hot tanked. There's no way I can clean the covers by hand. I've been looking at Ebay for parts, any of you have good sources?