Need help with destroyed thrust bearing

Built_for_Boost · Sep 12, 2015

I recently bought a used 6 bolt long block engine off of Craigslist for $425. I originally bought it to take apart and further increase my knowledge of the internal combustion engine, but after doing research on the 4g63, I fell in love with the platform. I have since taken it apart to the block, and I have found 2 problems. One is that the thrust bearing was completely destroyed, due to what I believe was oil starvation. It appears that the bearing lost oil, started to melt, and then a piece went into one of the oil passages in the bearing. This then clogged one of the holes, making the situation worse.

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The crank also has a blackish blue shine to it, which I suspect is due to the massive amounts of heat it was subjected too. I want to know what I should do about this,i s the crank still usable?

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The bearings will be replaced, but what is stopping the situation to occur again. Has there been problems with the thrust bearings running on low oil.

The number 3 piston bearings also have excessive wear. Are these 2 incidents related at all?

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Thanks for your time.

jimsgsx · Sep 12, 2015

No oil will fry your engine. You are correct. Some of the 7 bolt engines had the revised split thrust bearings that are supposed to be better. I cant tell if the crank will be reusable by the pic.

Built_for_Boost · Sep 12, 2015

jimsgsx said:
No oil will fry your engine. You are correct. Some of the 7 bolt engines had the revised split thrust bearings that are supposed to be better. I cant tell if the crank will be reusable by the pic.

All of the other bearings look to be fine though. What would cause only the middle bearing (thrust bearing) only to run dry?

jimsgsx · Sep 12, 2015

Could have been a bad oil squirter, misaligned or bad clearance, maybe it was just a bad bearing to begin with. If i was you i would google around and do some research my friend. Best of luck to you.

Built_for_Boost · Sep 12, 2015

Thanks. Does anyone know if the middle main bearing and the 3rd connecting rod bearing are connected in any way?

BogusSVO · Sep 12, 2015

With that much heat, I would have the main bore checked in the block.

Some more of the back story could be helpful too.

Was the engine rebuilt before?

How are the thrust faces of the crank?

How bad is #3 rod throw?

Built_for_Boost · Sep 12, 2015

I bought the engine off Craigslist from a person who has lots of experience with DSMs. He got it from one of his friends, so he didn't have millage numbers, although the other person had it compression checked and it had 160s across the board. The person I bought it from said it could be built, because the engine had arp headstuds, and who would spend money on studs and not the other parts of the engine. So I pulled it apart to find arp headstuds, arp rod caps, 2g pistons on 1g rods, and acl bearings all around. It was built right at one point. The only thing wrong with the number 3 main cap is the top on bottom bearing. The damage doesn't appear to have spread to the cap itself. As for rod throw, I'm not really sure. I am taking my block and crank to get it checked, decked, honed, crank polished and balanced as needed. Hopefully they can offer insight on this. Worst case is I need a new crank right? Almost no shavings in the pan, maybe 2 very small pieces in the pick up and strainer.

Built_for_Boost · Sep 12, 2015

Built_for_Boost said:
Thanks. Does anyone know if the middle main bearing and the 3rd connecting rod bearing are connected in any way?

I'm talking connections in terms of oil delivery if that was not clear.

BogusSVO · Sep 12, 2015

So #3 main cap was on backwards, facing the wrong way.

That tells you right there what happened to the thrust bearing, now the block stands a very good chance of needing to be line honed/bored.

You mean the rods have ARP rod bolts.

The 2g pistons, in stock form, have 63DTF1 cast in the crown of the piston.

IIRC, Main 1 feeds rod 1
Main 2 feeds rod 2
Main 4 feeds rod 3
Main 5 feeds rod 4

Check the engine ID area, and the oil pan rails for a builder ID stamping or scribings.
Look close at the head gasket surface and see if it looks belt surfaced.

Built_for_Boost · Sep 12, 2015

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Yeah, I meant rod bolts. And how could you tell that the main cap was on backwards. There are some markings on the block. Not sure if those mean anything.

BogusSVO · Sep 12, 2015

I may have miss read but you made it sound like you found the main cap on backwards.

Those marks on the block are from the factory build.

Built_for_Boost · Sep 12, 2015

The main cap was on normally when I took it off.

BogusSVO · Sep 12, 2015

Arrow pointing towards the front, bearing notch to notch?

Also having ARP head studs means nothing about the bottom end being built. There are more than a few on here that have installed ARP head studs when replacing a HG. It is rather common.

I also suggest you have the crank checked for straight, and if that is good have the oil galley balls removed so the crank can be cleaned.

Also take the rods and have the big ends checked.

Built_for_Boost · Sep 12, 2015

Yep, that's how the bearing caps were. And I'll tell the machine shop Im taking my engine to do what you said. They specialize in DSM cars, so they should know what to do. Thanks for all the support and help.

WREKLESSRACR · Sep 13, 2015

I have a crank that is blue from heat. Machinist suggested it may have been welded or experienced some bearing failure as you suggest. I just swapped cranks. Let me know if it passes if you get it checked out.

Built_for_Boost · Sep 13, 2015

WREKLESSRACR said:
I have a crank that is blue from heat. Machinist suggested it may have been welded or experienced some bearing failure as you suggest. I just swapped cranks. Let me know if it passes if you get it checked out.

Ok, ill keep you informed. How much was your new crank btw?

miliman13 · Mar 19, 2016

Built_for_Boost said:
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Yeah, I meant rod bolts. And how could you tell that the main cap was on backwards. There are some markings on the block. Not sure if those mean anything.

But what does it mean???

EGLTAWLN · Mar 19, 2016

those punched scribe marks are the factory bearing measurements. 4 marks for the rods, 5 marks for the mains. scribed in roman numerals.

miliman13 · Mar 19, 2016

mines appears to have a few more than that pic.

you say measurements ? i apologize if i am not following but......... what?? measurements in the bottom end go into the
( tenth- thousandths , 0.0001) so how is that detailing that info?

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