In the middle of my rebuild I discover that my crankshaft have been ground -0.10mm. I Need new bearings, but Simon doesnt have them
Lars
I know most of you on this forum are used to measurements in metric, but we have to be very careful in quoting engine undersizes, since although this engine family (1639/1812/1984/2215cc) was made in Europe and generally metric measurements, it was designed in England to originally imperial measurements. Why do you think the cylinder head block face to cover face is exactly 6 inches with a tolerance of 4 thou? Why does it have many non ISOmetric 7 mm studs and bolts - they were originally 1/4 inch (which is larger than 6 mm). Why is this important? Because in the U.K. our undersizes were generally 10, 20, 30 and 40 thou. (thousandths of an inch) So the first undersize of 10 thou is equivalent to 0.25 mm whereas when you talk of 10 under meaning -0.10 mm that is only 4 thou. It is unusual to regrind a crank journal or big-end pin to 4 thou undersize. Most engines needing regrinding will have already gone past the 4 thou undersize. So that size was really only for either badly machined original sizes or when cleaning up an otherwise good crank to put in new shells.
These days it is possible that certain bearing shells or crankshaft thrust washers meant for another engine may fit, but if they are made for an English engine the undersizes will be imperial not metric. This is why there are 0.20 mm and 0.25 mm undersizes. The latter are really 10 thou undersize.
So when you specify an undersize you need to make sure you specify whether you are talking about mains (10 half shells) or big-ends (8 half shells) and imperial or metric. Finally you should NEVER have a crank reground without first having the bearing shells and providing the machine shop with them. Why? Because if they have the shells that will be used they will (or should if they are good) make sure the crank is ground to a good fit for the new shells. If they only have the crank and grind it to a specified size, then find the shells are not quite right, they have to do the job over and may even have to take more off to go to the next size. e.g suppose you had it ground to 0.25 mm (10 thou) under and then found the only shells available were -0.20 mm or -0.50 mm You would then have to go to the -0.50 mm size as you were already past the -0.20 mm dimension.
I have and can get undersize shells and thrust washers for these engines now but one set of undersize shells I have for the big-ends is '10 under' - that is 10 thou under, therefore -0.25 mm. And some of the packets for these parts are marked with other manufacturers names - like Vauxhall and Rover.
Hope this helps clarify things a little.
Roy