Bearing clearance

In the case you find a tight bearing clearance what is to be done to correct

Hi

There are a couple options in terms of correcting bearing clearances. The easiest way is to order thinner bearings. Many manufacturers will have different thickness bearings for almost all applications. For instance, I was working with a crankshaft that was in good condition however 2 of the journals were larger than the rest but still within tolerance. I ordered one set of bearings expecting my clearance would be tight for the 2 journals, which it was, at .0012". My target was .0020-.0022". To correct this I ordered a set of .001" extra clearance bearings and used them to correct the clearance and I got the 2 journals back to my .0022" target. I've even had to mix bearing shells to achieve the exact target i.e. (using 1 std half and 1 .001" extra half for a net .0005" additional).

Another option is to have the crankshaft machined down to a smaller diameter which is more costly, but may be beneficial if the condition of the crankshaft is less than ideal to begin with. This way you can likely use only one set of bearings and the crank will be freshly refurbished.

The final option is to have the bearing tunnel line honed/bored for the mains and rod bores. again, more costly but if both are less than perfect this may make more sense anyway.

Hope this helps

A couple of other options, while the supplies bearing shells are helt to a tight tolerance during manufacture, there is still going to be very slight valiations, so you may be able to swap them around to get what you need.

Rather than regrind the journals, as such, a competent machine shop should be able to polish the journals to get the clearance you need.

I assume you've double, and triple, checked your figures?