4000 miles = bad bearings?

[lobo2112]

ok, so I had my engine rebuilt 4000 miles ago and due to an over tightened timing belt (my fault) which snapped my timing belt pulley bolt, I have some bent valves. while replacing components I noticed that my rod bearings on 2 of my rods are already all scratched up and theres a nice scratch on my #6 journal. Also those scratched bearings aren't fitting right in the rods, the seem pinched theres about a 1-1.5 mm gap between the face of the rod and the matching face of the bearing. so, fearing crank damage i started pulling the crank. the girdle side bearings are already starting to show copper coloring and 1 of the bearings on the engine side has a bunch of pits in it. WTF is going on? all of this stuff is machine shop assembled. poor machine shop work? poorly finished/remanufactured crank? (it's a reman forged crank, +10/+10 "new" as of 4000 miles ago) part of me is relieved that my mistake may have saved me from a more costly spun bearing down the road, and part of me is pissed off at what seems to be poor machine shop work that i paid extra on for him to spend extra time making sure the tolerances were within spec.
Is it normal for the bearings to be showing copper?
what would cause the bearings to pinch like that?
my block was decked and align-bored to repair damage done by the spun bearing causing the original rebuild... is that at fault?
any other suggestions you guys can throiw out there will help alot.

[DCIV]

I am going to go ahead and say that I think the tensioner and pully bolts should be replaced at the 120k. I streched my tensioner bolts and at least figured it out before they broke. I bet thats more along the lines that happened to you because I dont think the timing tensioner could put enough tension on the belt to break that bolt.

The next question please get pics for us.


Coop

[Import Power]

reman crank?

I will say it agian. Do not use reman cranks.

-Chris

[donniekak]

Scratches and scores speak more for oil contamination than a bad crank. What were your oil clearances when the engine was built? Was it the 2 center mains with the most wear? Oh, by the way the rod bearings should conform to the rod when the bolts are torqued down.

[3startuna]

It sounds like a combination of poor lubrication and not checking your tolerances when you built the engine.

Also where did you assemble the shorty?

[lobo2112]

As stated in my post, a machine shop assembled the short block. the rear 3 main bearings show wear, with the #3 bearing showing the most copper on the cradle side. and the front one on the engine side is the only on on that side showing wear/pits. the forged reman crank was my only option, the old cast one was bent in 2 places and twisted due to the spun bearing causing rebuild #1. I realize the rod bearings should conform to the rods, the question is what would cause them to be pinched the way they are. they sit VERY loosely in the rod caps particularly. 1-1.5 mm of slop. as for the wear on the bearings should they already show copper? we were undecided as to whether or not they should once properly broken in, I was leaning towards no but want verification. I was under the impression it was time for them to be changed once they started showing the copper material.

[donniekak]

I've seen 100,000 mile motors that didn't show copper. Some thing is wrong. Sound like a lubrication issue as stated before. Can you get some pics of the bearings? Does your oil pan have a dent in it?

[3startuna]

actually the reason I asked you where it was assembled is a very important question. I asked my machinist to assemble my block and he refused. He said " A machine shop is the wworse place to assemble an engine, their is just too much chance for metal filings in the air to get into the engne during assembly.

With these things you have to be monk level of anal, when assembling a bottom end.

I even cut my finger nails prior to assembly and cleaned all my tools with gasoline. I also wore clean clothes, and minimized how much i was breathing. Its really like doing surgery, when it comes to assembling the bottom end.

To be showing such levels of bearing wear means a couple things

1. Poor Lubrication (new oil pump used? what did they use to assemble? how did u break it in)
2. Contaminated oil supply/ dirty assembly
3. Bent crankshaft
4. Failure to check tolerances, both oil clearance, and thrust clearance.

How well was the block prepared prior to the build? U need to have that thing CLEAN!!!! as in soo clean its about to start rusting clean.

[phantomrt]

Originally Posted by lobo2112

ok, so I had my engine rebuilt 4000 miles ago and due to an over tightened timing belt (my fault) which snapped my timing belt pulley bolt, I have some bent valves. while replacing components I noticed that my rod bearings on 2 of my rods are already all scratched up and theres a nice scratch on my #6 journal. Also those scratched bearings aren't fitting right in the rods, the seem pinched theres about a 1-1.5 mm gap between the face of the rod and the matching face of the bearing. so, fearing crank damage i started pulling the crank. the girdle side bearings are already starting to show copper coloring and 1 of the bearings on the engine side has a bunch of pits in it. WTF is going on? all of this stuff is machine shop assembled. poor machine shop work? poorly finished/remanufactured crank? (it's a reman forged crank, +10/+10 "new" as of 4000 miles ago) part of me is relieved that my mistake may have saved me from a more costly spun bearing down the road, and part of me is pissed off at what seems to be poor machine shop work that i paid extra on for him to spend extra time making sure the tolerances were within spec.
Is it normal for the bearings to be showing copper?
what would cause the bearings to pinch like that?
my block was decked and align-bored to repair damage done by the spun bearing causing the original rebuild... is that at fault?
any other suggestions you guys can throiw out there will help alot.

How do you overtighten the timing belt? That is actually pretty difficult to do considering the engine has an automatic tensioner. What happened was you overtightened the tensioner bolt, which stretched and weakened it and it just decided to finally snap. Mitsubishi uses REALLY soft metal for their bolts and you have to use care when torquing them down. I don't know why they use such soft metal. When I had my Stealth apart for its engine rebuild, I broke several bolts during the project. I became sad and already started to make a list of extra drill bits to buy. Nope. NO problem drilling them babies out. I've never seen bolts drill out with such ease.

Anyways, back to the lower end issue. It sounds like a poorly assembled engine in Layman's terms. It is not okay for bearing copper to be showing already. Something was definitely wrong.

All but a few of the cars I've owned in the last five years had a remanufactured crankshaft in it, including my TT Stealth. There is nothing wrong with using one, but that is assuming it was remanufactured properly. I get my cranks from Crankshaft Supply in Minneapolis. They are the best there is and I've got to he point where I don't even bother to check their work anymore.

Your bearing problems could be anything. If the main bearing nearest the oil pump is the best shape and keeps getting worse until you're at the very rear of the engine, that indicates that those bearings were getting the least amount of oil due to excessive clearances, bad oil pump, blah blah blah. For the bearing and journal scoring, undoubtedly there was some debris in the oil galleys and stuff which caused that.

I'd definitely get the big ends of the connecting rods checked out. In this scenario, I would start all over and check EVERYTHING. Buy as much insurance (checking parts out) as you do in parts themselves.

I assemble all my engines in my less than surgically clean garage, which is flirting with disaster somewhat. Ideally, you want to be like you're working in a hospital. Clean every individual part thoroughly and re-assemble with clean hands, clean clothes, etc. Its very time consuming, but thats what you have to do to be successful time and time again.

[Import Power]

Originally Posted by 3startuna

actually the reason I asked you where it was assembled is a very important question. I asked my machinist to assemble my block and he refused. He said " A machine shop is the wworse place to assemble an engine, their is just too much chance for metal filings in the air to get into the engne during assembly.

With these things you have to be monk level of anal, when assembling a bottom end.

I even cut my finger nails prior to assembly and cleaned all my tools with gasoline. I also wore clean clothes, and minimized how much i was breathing. Its really like doing surgery, when it comes to assembling the bottom end.

To be showing such levels of bearing wear means a couple things

1. Poor Lubrication (new oil pump used? what did they use to assemble? how did u break it in)
2. Contaminated oil supply/ dirty assembly
3. Bent crankshaft
4. Failure to check tolerances, both oil clearance, and thrust clearance.

How well was the block prepared prior to the build? U need to have that thing CLEAN!!!! as in soo clean its about to start rusting clean.

These engines (6G72) are no different than any other engine on the planet.
It should be assembled Very carefully and clean, as with any engine. And it should be cleaned so that it will rust not about to start rusting. Hot soapy water bath, rinse and compresses air dry. At that point it should rust. BUT you then give it a quick fine coat of WD40. Then you clean the cyl bores with ATF, you will find more metal coming out. Once the towel is clean using ATF Brake clean off the ATF and lube with oil or assembly lube. Then use assembly lube on all metal to metal surfaces. Do NOT be afraid of using the lube.