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1990 trooper 2, 76 Datsun 620
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Discussion Starter · #81 ·
So I was spinning the crankshaft over just for the heck of it. It IS REALLY stiff, has nothing to do with a camshaft in there either. I’m wondering what is up here, because now it is actually stuck. I can’t get it to turn backwards either. Some idiot put this thing together or what?
 

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1990 trooper 2, 76 Datsun 620
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Discussion Starter · #82 ·
Best info I've seen was at this site:


Take heed of the Old Timer's advice on bearing position and also good ways to verify the position of each hole.

BTW, do your bearings have grooves on the outside of the shells? If so, ok can flow to the cam journals regardless of bearing position.

But there are rotational forces involved which affect oil flow to the upper end, and you don't necessarily want all the holes in the bearings aligned with their oil feed holes.

I urge you to study that thread carefully, the answers you seek lie within!
interesting input from those guys. since my block has big grooves behind where the bearing sits, I chose the 2 o'clock position, since I was installing dura bond and thats what they suggest. something about creating a pressure wedge forward of the load. That happens to line up with a hole. The shop had #2 and #3 with the hole at 6 o'clock which seems to be a no no?
 

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1990 trooper 2, 76 Datsun 620
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Discussion Starter · #83 ·
By the way folks, removing the messed up bearings and installing those SBC bearings in my 3.4 V6 was a breeze. I cant seem to grasp how the bozo that put the ones in I removed gouged them up so badly. I used a summit brand tool for the SBC, fairly affordable, worked perfect.
Unfortunatley, i will have to disect this thing to figure out where it is binding up. bummer
 

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So I was spinning the crankshaft over just for the heck of it. It IS REALLY stiff, has nothing to do with a camshaft in there either. I’m wondering what is up here, because now it is actually stuck. I can’t get it to turn backwards either. Some idiot put this thing together or what?
Check the thrust bearing. Years ago I was rebuilding an engine, and when I torqued all the mains down the crank wouldn't turn. The shop had neglected to machine the thrust surface of the crankshaft to account for the thicker thrust bearing. Just slack off the bolts on that main cap and see if the crank will turn.

If that's not the one, start undoing main bearing cap bolts until you find the problem. Hopefully it's not a tight rod bearing!
 

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1990 trooper 2, 76 Datsun 620
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Discussion Starter · #85 ·
After some frustrating troubleshooting, I’ve broken the crank damper bolt off in the nose of the crank and have gotten nowhere. When I loosen things up it does turn, but as everything goes back together it seizes up and I can’t determine if it’s main bearings or rod bearings. I’m doing this one at a time too. I need to get a good extractor bit set now.
 

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Is the crankshaft bent? You may have to take it out and have the machine shop check it. Also check all main & rod journal dimensions for proper sizing, and the thrust surface as well. That's a real Bummer!
 

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Say a few prayers that the bit doesn't break off in the crankshaft! Be Very Very Very Vewwy Carefulllllll!
 

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Discussion Starter · #89 ·
It’s a brand new crank, I know this because it says “3.1” on it. Yeah, I hate extractor bits too, this crank may be scrap metal now. Looks like I’ll have to size my own bearings too. What did I pay the shop to do again?? I’m confused.....
 

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More Fun! What you can do to check the crank yourself is go get some Green Plastigauge, # SPG-1. Loosen all main and rod bearings and verify the crankshaft turns without binding.

Then check the clearances, starting with the main bearings. One-at-a-time.


BTW, if that's a new crankshaft, all the journals should be Standard-sized. Are all your bearings marked "Std"?

Anyway, check each journal with Plastigauge for clearance. If in spec, clean off the squished Green Stuff, use Pre-Lube and install/torque to spec. Then see if the crankshaft will turn.

Rinse. Lather. Repeat. If you get thru all the mains with no binding, and good clearances, start with the rods loosened and check every journal.

Other than that, it's machine shop time; dump it off in their laps and tell them to fix what they Fouled Up.

 
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