[Bob Johnson]

I have read lots of opinions on how to check main and rod bearing clearances. There is something that confuses me. It is generally agreed that there should be 0.001" of clearance for each 1.0" of bearing diameter. On a B engine the main bearings are about 2". That would result in a bearing clearance of 0.002". The confusion, for me, is the following. Should the bearing be 0.002" larger than the crank journal? For example, bearing 1.999" and crankshaft journal 1.997". Or is that clearance a 0.002" gap all the way round the journal. Which would make the example bearing 1.999" and the journal 1.995"?

With regard to Plastigage. I have read conflicting instruction. Most say use one piece across the journal. There were also instruction to place two pieces across the journal 180 degrees apart. The first method would give an 0.002" difference (0.001" overall gap) between the bearing and the crank. The second would give a 0.004" difference (0.002" overall gap).

I have tried both and the 0.004" difference (0.002" gap) appears to be too much. The crank can be moved up and down producing a rattle noise.

What do you guy think?

Bob Johnson