Goodwrench 350 rod bearings seem too tight, what could happen ?

[mtnmankev]

The factory rod bearings were stamped .0006 but since a new set of those were not available, I had to go with .001 from my local machine shop.
According to the plastigage, I have less than .001 clearance.
I can turn the engine through by hand (still on engine stand), but it's a struggle..
Am I going to have any problems running the engine with the crank that tight?

 

[Blue Ox]

Not for long.

Double check the specs, but my book says .0012"-.0037" so technically even .001" is tight.

 

[mtnmankev]

Thanks, guess I had better order a set of standard then.
That SHOULD put the clearance where it belongs since .0006 are not available.

 

[QBuff02]

Have you measured the journals on the crank? Quite possibly it wasn't ground/polished correctly if those are the types of clearances you're getting from bearings with those specs you gave. I'd measure the rods and mains, or take the crank to the machine shop and have them check it out. What about the rods? were they machined or resized at all? they also could be undersized and crushing the bearings too tight. lots of things that need checked before you just throw bearings at an engine. and best case scenario you could have the machine shop polish up the crank and give you the extra clearance that you need. If you put it together the way it is, it won't run for long..
I guess I should add that the crank could be bent possibly, and that should be checked as well. But bearing sets 99% of the time come in standard, .010, .020, .030 undersized, etc. that's an odd ball for sure so I'd be double checking everything. But I'm also pretty fussy putting an engine together and everything has to be perfect.

 

[mtnmankev]

I don't have what it takes to measure the crank as I would want to, and the machine shop is 130 mile round trip and it would take two trips at the least.
The engine has never seen any disassembly since new, so no on the resized rods.

 

[Blue Ox]

Wouldn't surprise me that the factory has bearings in oversize/undersize increments to get correct fit and/or compensate for manufacturing tolerences. They do it with pistons, why not with bearings?

 

[bucket]

Wouldn't surprise me that the factory has bearings in oversize/undersize increments to get correct fit and/or compensate for manufacturing tolerences. They do it with pistons, why not with bearings?

Yeah, GM has done it with rod bearings too. I'm not sure how often, but I've seen it on a few that I've pulled apart.

 

[HotRodPC]

Yeah, for .0006 I'd have done some quick math and just gone with standard from the get go. Not sure why GM would have even worried about .0006 unless it's what they happened to have had. I've never heard of bearings in that size anyway. Kinda makes me thing the bearings may have been made out of spec but they marked them as such and used them anyway.

 

[mtnmankev]

Okay guys, I feel stupid now but also am relieved that things seem to be working out.
It seems that I had a brain fart senior moment, and when I looked at the bearings that I had removed, come to find out the mains were .0006 and with .001 installed, the crank plastigaged .0015 and it spins smoothly in the block, no glitches.
So no concern there.
The rods were standard and I replaced them with standard.
It seems when I installed the pistons, I didn't lube the cylinders quite as much as I should have.
Add some additional oil to them, turn the engine through and it's normal, ready to assemble and run.
And I only lost half a night's sleep worrying about the engine ........
Now to figure out why I was able to remove the flex plate from the crank while the block is attached to the engine stand, but now I can't get it to slide back into the sweet spot that seems to have vanished.

 

[mtnmankev]

This was the OEM #2 main bearing when I took the 350 apart, sorta explains why I lost oil pressure as soon as the oil began to warm up......

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[mtnmankev]

And I am glad it happened, this is what I found for remnants of the factory head gaskets.

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[MikeB]

Do you know how many miles were on that engine? Must have been severely overheated at some point.

I'd really clean up the block decks and check to see how flat they are. And make sure to use a .038"-.041" gasket vs. an .028" on those old surfaces. In the ideal world you'd have the decks surfaced, along with the heads.