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MG MGB Technical - Crankshaft thrush washers

The new thrush washers are too large and don't allow any clearance between the crankshaft and the thrush washers. What is the best way to reduce the thickness of the thrush washers?

George
G.E. Bulwinkle

George Its common practice with MGB engine builders to reuse the old crenkshaft thrusts. This is a common problem and If you do use the old thrusts reverse them. Rear one to the front as its only the rear that will have any wear. Even a mixture of one old and one new will work. You can dress down the new thrusts but it should be the steel side as its possible to deposit grit in soft surface otherwise use a bearing scraper. Check the new thrusts for warp as this has been reported lately.
Denis
Denis4

George. There are two sizes of crankshaft thrust washer: standard size and +.005". The first step in resolving your problem would be to make sure that you have standard sized thrust washers rather than the oversized ones.

Assuming that you are rebuilding an engine and have not interchanged blocks and crankshafts, the standard sized thrust washers should fit and give the proper end float--it did when it was built and parts tend to wear and open up the end thrust, not close it up.

If the thrust washers need to be thinned, the best way to do so is to glue a sheet of emery cloth to a flat glass plate and run the thrust washers over the top until you have the desired thickness of washer. This can also be done by holding a piece of emery cloth on a flat surface and dragging the thrust washer across it, but that method takes longer than the glued onto a glass plate method. Use a set of dial calipers and carefully measure each of the thrust washers, then start thinning the thickest one until it is the same thickness as the next thickest. At that point, carefully clean the washers, install and retest for end float.

By the way, you are testing with the crankshaft and bearings dry are you not? Oil can have an effect on any measurements taken. It would also be good to know how you are measuring the end float and the thickness of the new washers you are using. They may not be made to the proper standard.

Les
Les Bengtson

George, are you saying that they are too thick to be inserted, or that the shaft is tight to rotate when they are in? Or you have zero end float?
Art Pearse

I rebuilt the engine two years ago. Installed the thrust washers. Too tight and zero clearance. Have to pull the engine due to a failure of the freeze plug between the engine and the gearbox. Engine ran ok but the fuel economy was terrible.
G.E. Bulwinkle

George. Once again, there are two sizes of thrust washers. We need to know what size you used. It would, also, be good to have the actual thickness measured with a pair of dial calipers or a micrometer, so we can compare with a set of stock thrust washers. Until we know what you have, it is difficult to make actual recommendations as there are so many variables, including, if the crankshaft was turned down, if the job might have left a ridge that was binding on your current thrust washer set. Please let us know what you find after you have taken the engine apart. Tight thrust washers should have worn in after two years of use and should not be causing poor fuel economy at this point.

Les
Les Bengtson

Ok I put the original thrust washers in. They measured .092 thickness. New ones measured .095. I guess I had used the original washers when I rebuilt the engine. Checked the end float with a dial indicator- .004 inches.

George
G.E. Bulwinkle

This thread was discussed between 19/05/2014 and 26/05/2014

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