Crank undersized on several journals?
Thread Starter
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Tuned
Joined: Feb 2017
Posts: 467
Likes: 21
From: Austin, TX
Crank undersized on several journals?
Morning all,
My crank was ground 0.030 under at some point. Found the last full set of 0.030 under conrod bearings in existence it looks like. Put them on, everything good until bearing #5. Anything past finger tight torque on the nuts seizes the whole motor. Ordered new plastigauge to investigate this one but was it common to grind 5 journals to 0.030 under and leave the #5 journal original? Haven't had a lot of time recently to tinker, back to back to back weddings and work travel but would that be a realistic scenario or do I have a bigger problem to address?
Alex
My crank was ground 0.030 under at some point. Found the last full set of 0.030 under conrod bearings in existence it looks like. Put them on, everything good until bearing #5. Anything past finger tight torque on the nuts seizes the whole motor. Ordered new plastigauge to investigate this one but was it common to grind 5 journals to 0.030 under and leave the #5 journal original? Haven't had a lot of time recently to tinker, back to back to back weddings and work travel but would that be a realistic scenario or do I have a bigger problem to address?
Alex
Logistics Pro
Joined: Sep 2014
Posts: 4,920
Likes: 21
From: Bothell & Silverdale, WA
It was sometimes a practice to turn all mains or cons and vice versa, but to just turn some of each is a very poor practice, and was probably performed by a midnight machine shop.
Senior User
Joined: Sep 2017
Posts: 111
Likes: 2
From: Eastern Shore, MD
You are using assembly lube....right??
Some long cranks can have a very small bend in them, so try mounting #6 and then come back to 5 and see if it clears up. Is the thrust bearing on #5?? that could also be binding a bit until you smack the crank back and forth a few times. My guess is you don't own a mic??
Some long cranks can have a very small bend in them, so try mounting #6 and then come back to 5 and see if it clears up. Is the thrust bearing on #5?? that could also be binding a bit until you smack the crank back and forth a few times. My guess is you don't own a mic??
Thread Starter
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Tuned
Joined: Feb 2017
Posts: 467
Likes: 21
From: Austin, TX
You are using assembly lube....right??
Some long cranks can have a very small bend in them, so try mounting #6 and then come back to 5 and see if it clears up. Is the thrust bearing on #5?? that could also be binding a bit until you smack the crank back and forth a few times. My guess is you don't own a mic??
Some long cranks can have a very small bend in them, so try mounting #6 and then come back to 5 and see if it clears up. Is the thrust bearing on #5?? that could also be binding a bit until you smack the crank back and forth a few times. My guess is you don't own a mic??
Fleet Owner
Joined: Jul 2004
Posts: 27,290
Likes: 1,055
From: NM
I havent heard of leaving one journal stock, but I have heard of a box of bearing shells having a set or two of the wrong size shells in it. The shells are usually marked on their backs.
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Thread Starter
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Tuned
Joined: Feb 2017
Posts: 467
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From: Austin, TX
Thought of that. Swapped it out with another bearing I bought from Egge 0.030 under..same problem. Unless two bearings were both mismatched on separate orders from separate shops, I think the issue isn't the bearing being wrong in the box.
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Logistics Pro
Joined: Sep 2014
Posts: 4,920
Likes: 21
From: Bothell & Silverdale, WA
Ok, here's what I would do. Remove the crank and bearing inserts and then torque down the bearing caps and check the ID with an inside mic. Also mic the crank journals. It could remotely be a line bore issue.
You can also compare the torqued down cap ID with the new and old bearing inserts.
You can also compare the torqued down cap ID with the new and old bearing inserts.
Cargo Master
Joined: Aug 2014
Posts: 2,594
Likes: 72
From: North Central Arkansas
Alex, You need to pull the crank and mike all the journals to see what you have. Chevrolet is notorious for grinding one journal odd on new engines if they have one journal messed up in the manufacturing process. The previous rebuilder of your engine may have done the same thing. The only way to tell what you have is to mike the crank.
Mark
Mark
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Tuned
Joined: Feb 2017
Posts: 467
Likes: 21
From: Austin, TX
Everything turned perfectly when I took it apart but the old bearings looked a little on the worn side (see rebuild log for pics) so I got NOS bearings. Plaque on the side of the motor says crank 0.030 under. I'll start with the plastigauge tonight and identify if I don't have enough clearance.
Senior User
Joined: Oct 2015
Posts: 415
Likes: 1
Probably turned all but one .030 and the other cleaned up,at .020 so they just left it and used a different bearing insert. Not a great practice but some cheap rebuilders tended to go cut whatever costs they can and the truck will run fine going this route. I’ve heard of people finding a single cylinder bored oversize as well. It seems that would be more noticable.