Rear main

[31 RPU]

Where could I find a rear main that is .020 or .030 oversize?
Who sells them?
Thanks

[Tom Wesenberg]

Originally Posted by 31 RPU

Where could I find a rear main that is .020 or .030 oversize?
Who sells them?
Thanks

Oversized, or undersized?
If the Model A crankshaft has been turned .020", then you need undersized babbit in the caps. It would be thicker by .020", but the actual diameter is undersized.

[BRENT in 10-uh-C]

Tom, wouldn't the Babbitt need to be oversized to make up the difference with the crankshaft journal being undersized?

[George Miller]

Tom is right it is called a undersize bearing. If it was a insert you would ask for a .020 under size bearing.

[31 RPU]

Yeah that's what I meant. I was referring to the crankshaft. Sorry about that. Rough weekend I suppose.

[31 RPU]

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But , then again it's how you look at it. It would be an oversized bearing cap and an undersized crank journal...?

I think I found one at Ron's machine shop

[MikeK]

A clear case of inverse postulatum. If a hole represents an area of nothing and you make it bigger, do you have less?

[Kohnke Rebabbitting]

Originally Posted by 31 RPU

But , then again it's how you look at it. It would be an oversized bearing cap and an undersized crank journal...?

I think I found one at Ron's machine shop

No, it would be an under size crank, and an under size bearing.

So, if the crank is .020 under size, and the bearing is .020 over size, then the oil, or shaft clearance would be .040 thousandths.

[George Miller]

Calling a .020 under size bearing over size is like calling a brake shoe a brake pad. It just is not right. We have been calling them under size bearings all my life.

[J Franklin]

Time to re-babbit

[40 Deluxe]

"Undersized" is the correct term. Here's why: Say a crankshaft journal is factory machined at 2" diameter. That would make the inside diameter of the bearing 2.001" or 2.002", for oil clearance. After many miles, the crankshaft journal wears out-of-round. To avoid needing a new crank, the old one gets it's journals ground down to make the journal round again. Say it required grinding off .010" of metal to make it round. Now measure the journal and you will find a diameter of 1.980", which is less than the original 2", thus the shaft is now 'undersized". And, of course, the inside diameter of the bearing must also be reduced, to 1.981' or 1.982" for proper oil clearance. Thus it, too, is "undersized".

[SLPreston53]

31 RPU asked about where to get a rear main! Here is my answer: J Franklin (#10) is right. While I know in the old days Ford did sell main caps off the shelf, with the technology we have, I think it would be pretty hard, or at least a big production to pour and then cut just a main cap. One solution might be to check whatever non-running engines you might have access to and see if there is a rear main in one of them that is useable and the right size as a patch until you can get the engine re-babbited.

[Joe K]

Originally Posted by MikeK

A clear case of inverse postulatum. If a hole represents an area of nothing and you make it bigger, do you have less?

Sound like something Stephen Wright would say!

http://www.weather.net/zarg/ZarPages/stevenWright.html

Joe K

[Pete]

Originally Posted by Joe K

Sound like something Stephen Wright would say!

http://www.weather.net/zarg/ZarPages/stevenWright.html

Joe K

OK, so what's the speed of dark?

[Kohnke Rebabbitting]

Originally Posted by Pete

OK, so what's the speed of dark?

It must just be a little faster then light to keep from getting run over!

[glenn in camino]

I collect good ones at swap meets. You never know when you might need one.