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MG MGB Technical - what do 3 bearing pistons look like

Hi, Can anyone tell me how I tell 3 baring pistons from 5 bearing pistons. I have been offered a set but without stripping my engine to look how do I tell if they are 3 bearing (the owner does not know)?
dave

Hi,
On the three bearings engine,at the rear of block in camshaft location, you have the housing for the rev counter drive,and the drive cable for the mechanical tachometer.
Regards
mw michel

Thanks, I already have a 3 bearing engine so i know what one looks like. I need to know how to identify pistons
dave

Dave, I'm not sure there are visual differences. The wrist pin/gudgeon pin diameter in the 3 bearing engine is .7499" to .7501". The piston pin diameter in the 5 bearing is .8124" to .8127". You should be able to measure the piston pin boss diameter and determine if you a getting 3 bearing pistons.

Clifton
Clifton Gordon

Dave,

18 G and 18 GA engines were fitted with solid skirt pistons and had angeled big end conrods that were fabricated with a small bolt at the split small ends to clamp the gudeon pin.
Later engines used circlips or had press fit pins and had 'pockets on both side ot the skirt to axept the fitting tool for the gudeon pin.

hope this helps

Ralph
Ralph

Search ebay Motors for: Item number: 180148828726

The pictured items might be what you're looking for.


Steve Buchina

If the wrist pins have a notch they are 3 main. If they have no notch and circlips at the ends they are 5 main (except for late clamped pins = no notch + no circlips)
Bill Spohn

Of course, Bill has remembered the easiest way to tell the difference.

cheers
Ian Buckley

This thread was discussed between 13/08/2007 and 16/08/2007

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