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MG Midget and Sprite Technical - 1275 undersize thrust washer from factory

Hi All

Just building a 1275 engine that had never been stripped before, tried new thrusts only to find they were dead on size so the crank wouldnt turn...zero endfloat. Checked for damage on new thrusts....perfect and no damage on crank. Checked old thrust washers only to find that one side was three thou under and marked as much too, not hand marked but machine marked M G W 003 u/s. I have never seen this before has anyone else? I popped the three thou under in and achieved three thou clearance....spot on!

Peter
P Burgess

I had to make a set of STD bearings thinner to fit, even though the crank journals where -0.20 Don't remeber what was on the old ones.
Alex G Matla

Peter,

I had a FIAT twin cam that had an odd non standard oversize piston, IIRC 1/2 way to the 1st normal oversize. The local FIAT dealer said they didn't exist. Another chap that had been dealing with engines for years asked if it was number 3, which it was. He said companies often have ropey boring machines which sometimes turned out bores out of spec so they had some special pistons to fit after the bore was honed to suit. Couldn't get them for love or money and it was the only one damaged.
David Billington

It just came as a surprise as I hadn't seen it before. Three thou tight on the gap between the thrust faces on the crank seems a lot. It must have been enough times to warrant making 'proper' thrusts! Maybe it was a whole batch of cranks :)

Peter
P Burgess

I had to sand my trust bearing down also...I dont remember the clerance but it was em-moveabley tight, luckly someone here said to get a sheet of glass some wet dry sand paper and some WD40 and sand the one side down in a figure 8 motion...It took awhile but i got it there clearanced out perfectly.

Prop
Prop

Hi Prop

I trust you are ok and well? I have a little magnetic bed grinder for reducing thrusts...usually oversize ones to get 'em just right!

Peter
P Burgess

This thread was discussed on 06/07/2010

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