Quote:
Originally Posted by Neil Harvey
Good luck trying to do it as above.
We have ground inserts each measuring the main housing size that go into the case in place of the #8 bearing. The case halves are then bolted together and we insert a dowel pin to hold the case halves in place. Then the case halves can be line bored with the dowel pin holding. There is little tool pressure when line boring, but the cases could still move if not dowelled.
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I did it with some difficulty but it wasn't that bad. You just zero the bore gauge with the measuring tips on either side of the case part line, then rotate just enough so that they are on the other side of the part line. Any different from zero on the bore gauge is misalignment. You are basically checking the #8 journal for out of round and correcting it with a mallet before you cinch down all the case bolts to perform your measurements.
I can see if you built a number of engines and time is money, you'd invest the time in a means of aligning the case such as Neil has.I was going to bore out an old #8 bearing but the lathe I have access to wouldn't hold it in the 3 jaw chuck so made do with the factory way.
Back to the subject of measuring the bearings, this is the anvil mic I bought. Like any relatively cheap tool you'd want to check it for accuracy and make allowances but in my case when I checked it against my mitutoyo 1" mic they were in agreement to within a fraction of a tenth of a thou. Close enough for the large clearances on these motors. You could run tighter clearances (and use a thinner oil) if you wanted but it seems the bearings that are easily obtained will give you clearances better suited to 10W40 or 20W50 etc.
https://www.ebay.com/itm/1-Dual-Ball-Anvil-Micrometer-Pipe-Tube-Round-Carbide-Tip-Wall-Thickness/231361340781?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649