I have driven the Blazer just a few times locally since March 1. On one of the few occasions I drove it, a woman managed to pull right out in front of me and I t-boned her. Her insurance paid nearly $3000 to have my vehicle fixed and I have had it sitting at home unused since May 1.

Definite rod bearing knock has developed on last couple of trips - much worse than before - now hammers pretty bad at anything above 2000 when warmed up, even with lightest throttle - and lifter ticks loudly. Took the engine back out yesterday. Changed oil and ran it for just a bit before pulling the engine to try to clean things out a bit - previous oil was full of metal. Funny - only took 5 hours to get it out and on the stand this time.

I hope I can determine a reason for the second bearing failure, that it is the same reason as for the first failure, and that I can actually fix it. It's going to be interesting.

 

Jesus, soo this is number 2 on rebuild that's suffering from this??? The 1 st rebuild lasted how many miles? Sorry, but it seems like u should've maybe went with a gm good wrench motor the first time.....I hope this is the last time u have it apart!!!!

 

Engine lasted 2000 miles or so before bearings went out again. If I would have known all the trouble I was in for, I would have done the crate motor. It just seemed silly to not fix a 65K mile engine at the time. Now I have too much money invested to not fix it.

Tore bottom end apart last night, Problem is not thrust bearing as the root of all problems like I thought it would be - it is at 0.006. However #1 main and #1 rod bearing are highly worn in comparison to the others again. This time I definitely have to find the reason. Machine shop was supposed to have checked bearing bores for straitness and out of round - came back saying they were fine. They resized the rods and ground the crank. Unless I screwed up the bearing install, all should have been just right. I have a hard time believing I screwed up the install as I took great care and have done bearings many times, but that remains a possibility. A lot of things need checked.

 

Did you verify all the oil passages in the block and crank were free and clear to that bearing? A clogged port would cause this.

 

I didn't run a wire through every oil passage, but I did inspect all crank oil holes and oil hole location for the new cam bearings. Agreed a lot of things need checked.

Last night I checked the main bearing bores for alignment using a new machinist's straight-edge that I bought. Main bearing saddles in the block are less than 0.001 out of alignment for all four with caps installed and torqued (without bearings). The heads are still in place on the engine, but the intake has been removed.

Main bearing caps appear to be less than 0.001 out of alignment for #1, #3, and #4 - but #2 Main cap measures 0.002 clearance with feeler guage when straight edge is laid across the rest. Could be that #1 is holding the straight edge away from #2 or that #2 alignment is really off. Need to determine which it is and maybe reinstall/torque #2 cap again/remeasure. Also don't really know how much misalignment on the bearing bores is permissable - need to look up this spec. I would imagine that 0.002 is significant and if any are out of alignment, based on the bearing wear seen on #1, I would guess that might be where the problem lies. I'm going to concentrate my looking in this area, and also want to determine if there is any reason why #1 main journal would not be oiling well (apparent lack of oil also took out #1 rod bearing and this is what I was hearing). At this point I think I need to either buy an inside mike setup to check the bearing bore diameter and check for out of round myself, or take things to the machine shop and pay them to do it. From a practical standpoint need to make a decision if further machine work needs to be done/redone on the block or rods. That will determine if I will be able to get away with not taking the heads off or pistons out (I think it's probably a pretty big long shot to just be able to spin a crank in).

I think it is interesting that the excessive #1 rod/main bearing clearance was causing the original misfire codes to be set again, even though the thrust bearing was OK this time. I had previously blamed it all on the thrust bearing whacking out the crank sensor by allowing the crank to walk back and forth. Looks like the thrust bearing was just a casualty. Moral I guess is that a loudly ticking lifter and a SES with false misfire code can definitely be due to excessive bearing clearance. Thrust bearing apparently doesn't have to be out for a false misfire code to set. Maybe this is the source of a lot of mysterious PO30x codes.

 

Well, good luck to ya!!! I hope u find the actual source of the problem!!! Maybe u need a different machine shop? I agree almost seems silly to just scrap a 65k motor , however ask captain I've learned a thing or two about rebuilt motors!!!! Let's just say if it isn't a Jasper then it better be a oem crate motor for me.........I just put mine back together after having the heads redone on a low mile rebuilt motor!!!!! It was a big name motor (Marshall) moral of the story they cut corners and it ended up costing me $$$$$

 

From post #8: I wonder if somewhere along the line the intake was incorrectly torqued? Check this warning, straight out the GM shop manual:

 

Yeah, I paid attention! That's why I asked the machine shop to check the line bore on the engine before they did anything to the block the first time. They claimed all was fine there and it didn't need line honed or line bored. I was really surprised.

Now when I check the center of the main bearing saddles in the block with my straight edge, they are indeed fine at <0.001" alignment. However, when I flip the engine over and check the center of the bearing caps torqued without bearings, I get 0.002 under the straight edge when looking at #2 cap. The rest of the caps seem to be in alignment. (If #1 was holding the straight edge up 0.002 away from #2, then I would think I could get a 0.001 feeler gauge under #3.) Difficult to definitively blame the machine shop at this point, since the #1 bearing was pretty loose and lost it's crush in the cap. I'm guessing it's going to need a line bore, but I want to figure things out before putting this block back into service.

 

Thanks!

Yes I do think I need a different machine shop. In any case they failed to help find and correct my specific problems (which I discussed in detail with them). Gotta be able to depend on what your machinist tells you.

 

Just got off the phone with a very helpful engineer at Mahle Technical Support (maker of the Clevite bearings that I used) who had agreed to try to help diagnose after looking at new bearing photos I emailed to him along with the history of the problems I have experienced.

He called back and said that he and several other engineers who looked at what I sent, all concurred without any doubt whatsoever that debris in the oil is what took out the bearings. Well, at least I now have my root cause and Mahle has made me a loyal customer. When asked about same bearings going bad they explained that circulating debris tends to circulate to the same places in the engine because of different flows, hence certain bearings can be damaged more severely than others.

So either the machine shop didn't clean things well before bagging my parts, or there may have been junk trapped in the oil cooler or oil cooler lines. Maybe someone forgot to wash something after machining, and it got out the door. I did clean the crankshaft, but I did not clean the block or heads and assumed they were ready to assemble. I also flushed out the oil cooler in the radiator and oil cooler lines with mineral oil. Guess I'll never know the true sounce of the debris. But I will change machine shops based on my experiences (right or wrong). Never had such a problem with debris in an engine in my life.

So engine will come completely apart for extremely thorough cleaning and inspection for damage. Oil cooler lines and radiator will be replaced and remote oil filter adapter will be removed and cleaned thoroughly. I guess I'll even disassemble the lifters for cleaning.