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Main Bearing Boring Question
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samstrader
Posted 2020-10-29 4:02 PM (#605031)
Subject: Main Bearing Boring Question


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Location: Beaumont TX		I have a 1955 259 V8 and my crank shaft was ground down too much.

Has anyone heard of getting the next small size of main bearings, .030 for example, and boring it out so it would fit like a .024 bearing?

I'm trying to figure out how to tighten up the my main bearings without pulling the engine. I think I can make the tool to use to change out the upper main bearings with the crank in the car and replace the bearings.

Thanks,

sam
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Powerflite
Posted 2020-10-29 8:33 PM (#605041 - in reply to #605031)
Subject: Re: Main Bearing Boring Question



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Location: So. Cal		No. Bad idea. Bearings are built with different layers that are required for long life & good wear. If you bore even .002" off, it will ruin it. A better idea is to get .02" bearings and add .001" to it by plating it with tin or whatever was the last layer on it. But don't go over .001" or .0015". If you need more than this, regrind your crank. But since your problem doesn't seem to be that acute, it may be best to live with it and run more oil through it with a higher volume pump.
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samstrader
Posted 2020-10-30 4:18 AM (#605053 - in reply to #605031)
Subject: RE: Main Bearing Boring Question


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Location: Beaumont TX		Thanks a lot Nathan. I didn't know this. Just thought it was like the babbit of the old days when they were poured. I looked at my pictures that I'm about to post for another thread and you can see the thin layer you are talking about. Here's a picture. Look at the edge of the bearing and you can clearly see the layer you are talking about. I didn't see this when looking at the actual bearing. It shows up a lot more on the picture.



Edited by samstrader 2020-10-30 4:20 AM




(Rear Main Seal.jpg)



Attachments
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Attachments Rear Main Seal.jpg (247KB - 151 downloads)
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57chizler
Posted 2020-10-30 1:08 PM (#605066 - in reply to #605053)
Subject: RE: Main Bearing Boring Question



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Location: NorCal		Some bearings like a basic bi-metal might be suitable for boring a little oversized but the multi-layer type can't. You'd want a .020" bearing to be able to bore it for a .024" journal.



(Bearing Layers.jpg)



Attachments
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Attachments Bearing Layers.jpg (31KB - 147 downloads)
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samstrader
Posted 2020-10-30 2:00 PM (#605067 - in reply to #605031)
Subject: RE: Main Bearing Boring Question


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Location: Beaumont TX		Thanks 57Chizler... I had no idea bearings were made like this now. I think my rear main bearing is the tri metal but not sure what the rest are. My rod bearings are probably the tri metal with cosmetic tin flash. Here are two pictures that show sort of what your diagram shows.



(Rear Main Seal.jpg)



(Rod.jpg)



Attachments
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Attachments Rear Main Seal.jpg (247KB - 148 downloads)
Attachments Rod.jpg (239KB - 145 downloads)
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