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main bearings - again, I know
Posted by: r3dplanet ()
Date: November 24, 2017 10:07PM

Hello.

I'm assembling a nice '65 case with a NOS standard size nitrided crankshaft.The center two bearing assemblies clamp the crankshaft when tightened to 50 ft/lbs with standard size bearings. It shows a little bear on the bearings when I spun it a few times. I felt tight but not crazy tight.

I've read a lot on this forum about how GM would measure the bare cases and pop in .001 or .002 undersize bearings as necessary. That's perfectly fine but with .001 bearings long gone, what's the next best thing to do?

I don't want to grind down a beautiful NOS crank. Just for kicks I popped in another crankshaft ground .010 under and used .010 bearings and had the exact same problem, so it's clearly a situation where the case is imperfect.

Someplace I read that you could pop in a .002 undersized bearing on one case half and a standard size on the other side, but I worry about throwing the crank out of balance.

What's the prevailing wisdom on this subject these days?

Cheerio.

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Re: main bearings - again, I know
Posted by: MattNall ()
Date: November 24, 2017 10:12PM

Something is a miss with the block.....

Undersize is SMALLER ID not larger...

If with a STD crank it rubs / wears / "bears?" on the shaft.... have that journal polished!





MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: main bearings - again, I know
Posted by: r3dplanet ()
Date: November 24, 2017 10:24PM

Oops. Pardon my nomenclature.

Yes, I'm trying to find what to do to allow better clearance hopefully without having to grind my NOS crankshaft. But if that's the only solution, then that's the only solution.

Thanks.



Edited 1 time(s). Last edit at 11/24/2017 10:26PM by r3dplanet.

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Re: main bearings - again, I know
Posted by: MattNall ()
Date: November 24, 2017 10:31PM

Not grind!! Polish!! Machine shop will know...

Have you Plasti-gauged the bearings yet?





MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
..............................110-PG.................................................Webered-Turbo

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Re: main bearings - again, I know
Posted by: r3dplanet ()
Date: November 24, 2017 10:48PM

I asked my machinist about polishing (not grinding) the crankshaft, and he's set up to do it. But he also said it's a last resort because it's very difficult to evenly polish the crankshaft perfectly for applications like this. He said he would do it only if I couldn't find another option.

So, I'm looking for another option. But if that's what need's be then I'll do it.

Thank you for responding.

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Re: main bearings - again, I know
Posted by: vairmech ()
Date: November 25, 2017 04:19AM

Did you tap or hit the case with a hammer to equalize the alignment as you torqued the case halves?

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: main bearings - again, I know
Posted by: jjohnsonjo ()
Date: November 25, 2017 04:34AM

On my last build, three years ago I had to try torquing three times until it would not bind up at 50 ft lbs. I tapped it at 5 ft lb intervals. Also, I did have it apart several times looking for problems. The one saddle had some baked on dirt which I cleaned the a scotch brite pad and that helped. What are you using for lube.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

Image and video hosting by TinyPic

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Re: main bearings - again, I know
Posted by: dryenko ()
Date: November 25, 2017 05:05AM

Are both line up pins installed?

Bob C aka Dryenko
Dobson, NC 27017

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Re: main bearings - again, I know
Posted by: gnrand ()
Date: November 25, 2017 06:46AM

Any history on the block? Have you measured the end play of the crank.
Jeff

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Re: main bearings - again, I know
Posted by: larry202br ()
Date: November 25, 2017 07:16AM

Like Matt said, plastigage!

1961 rampside with a 65 / 67 110 engine, car four speed.
Now I have 1965 convertible as well, got it running in June, autocrossed in July 2016 at the convention!

KC0SKX
Olathe, ks
HACOA

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Re: main bearings - again, I know
Posted by: Chilly Willy ()
Date: November 25, 2017 08:50AM

Has anyone line honed journals on a Corvair block?




The Corvair, Keeping Nader Notorious winking smiley


Will
Northern California

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Re: main bearings - again, I know
Posted by: Wagon Master ()
Date: November 25, 2017 08:57AM

No but I've taken .0005 out of a block journal with a bearing scraper.

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Re: main bearings - again, I know
Posted by: r3dplanet ()
Date: November 25, 2017 12:58PM

Wow, I didn't expect so many responses. Thanks to everyone!

Here are some more details:

1. Yes, I've been smacking the case halves with each incremental tightening sequence at 5-10 lbs. I've tried this many times and I've had the cases apart more times than I can remember.

2. Plastiguage shows almost zero play in the middle two bores. But at the ends it measures .0015" clearance.

3. The pins line up easily with no binding at all. The halves join together without any trouble at all.

4. End play is correct on the crankshaft. I have the clearance in my notes but I'm not at my shop right this moment. It wasn't a concern.

5. No, nobody has honed the journals.

6. I don't have the camshaft in right now. I'm just trying to get the crankshaft fitted at this stage.

7. I'll just add that the case is surgically clean. I constantly clean the innards after each attempt with white coffee filters and denatured alcohol until I cannot see any discoloration. The mating surfaces are smooth - I (LIGHTLY!) stoned them a while back to remove any hidden burrs, and I dressed adjacent surfaces with a little Scotchbrite.

... I'm told by a local builder that the best thing to do would be to run a quick hone in the middle two bores. I'm super not sure how to do that. I'm hesistant to go about polishing the crank because getting .0015" removed very evenly seems like way to much to polish, but I could be wrong. I get a lot of different opinions on polishing by people who build engines for a living, hence my confusion.

Again, thank you all for the brains. Lots of great input.

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Re: main bearings - again, I know
Posted by: jjohnsonjo ()
Date: November 25, 2017 01:53PM

Did you mic the thickness of the bearing shells, might be oversize and not stamped correctly?


How long was it apart? I have had mine totally apart several times over the years and torqueing the block halves never caused a binding problem with tapping. All the other times I was younger and it was only apart for days or a week or so. The last time it was apart for many many months and I had to retry a half dozen times. With and without the cam, changed lube type etc. Now I am thinking it had something to do with how long it sat apart. As in stresses built up in the case halves caused them to distort somehow.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

Image and video hosting by TinyPic

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Re: main bearings - again, I know
Date: November 25, 2017 02:19PM

Has anyone tried 0.001" shim stock between the case halves?

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Re: main bearings - again, I know
Posted by: Wagon Master ()
Date: November 25, 2017 03:23PM

That'd be ok but would only gain you clearance on one axis.
I don't see them listed separately and a set is about $100. Would you be interestedly​ in trying another set of standard center main bearings?


'29 Ford Model A Tudor
'61 700 Lakewood 110 4 speed
'69 Monza Convert. 140 Auto.
'70 Dodge Challenger R/T 440 4 speed

Been aircooled since 1973
Northwest Ohio

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Re: main bearings - again, I know
Posted by: vairmech ()
Date: November 25, 2017 05:35PM

OK, put plastigage in in each journal then lay the crank in and take it back out. Now measure each plastigage and see what difference there is and record it. Do the same thing for the other half recording the differences. Lay the numbers out and you just may see a pattern.

You may have to get a stick of smaller plastigage and you may have to press on the crank to get any reading. Be careful as you can flex the crank and get a false reading.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: main bearings - again, I know
Posted by: Frank DuVal ()
Date: November 25, 2017 06:06PM

Ken, you are saying not to bolt and torque the block halves, just set the crank in place and apply some hand pressure right? And do it for both block halves?

Frank DuVal

Fredericksburg, VA

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Re: main bearings - again, I know
Posted by: Wallygator ()
Date: November 25, 2017 06:16PM

If all clearances are correct you might check to make sure the crank is straight. That will cause it to be tight

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Re: main bearings - again, I know
Posted by: thewolfe ()
Date: November 25, 2017 06:16PM

A good dial bore gauge and micrometers will tell you exactly where the problem is. That is where I would start.

Nate Wolfe
Portland OR
65 Corsa 180

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