Crank polishing

[Alan Roehrich]

Most new racing connecting rods of good quality come in with a big end bore 0.0002" under the low limit as given in most machine shop manuals, for maximum bearing crush, which allows for the correct eccentricity with a racing bearing. Yes, you can get away with opening them up. But I prefer to avoid that. And I never use Scotchbrite on either side of a bearing, just a personal preference.

A good machinist can usually set up and take as little as 0.0005" off of the main journals. However, it will take a great machinist with a really good, tight grinder to take 0.0007" off of the rod journals. Asking a guy to do that, I'd think no less than $250 would be a fair price. Very few will even attempt it. There simply are not that many dedicated master machinists grinding crankshafts anymore, it does not pay what it is worth, given the low cost of the economy aftermarket crankshafts.

It will be next to impossible to polish a journal as much as you want and not have it out of round and tapered, possibly "hour glassed". No way I'd do that, either.

Are you measuring the bearings with the coating already applied? Because the coating is about 0.0002" per bearing half. If you are, that would put you at 0.0027" actual clearance, which, if everything is good, should be okay on a 2.5" journal. It might be on the tight side of ideal.