Re: Pouring Babbit?

Posted by Bob Carabbio on December 06, 1997 at 00:54:33

In Reply to: Pouring Babbit?
posted by Tony Olinger on December 05, 1997 at 23:32:26

Babbitt is getting to be a lost art (at least in the Dallas area).

If you tank an "A" block to clean it, it will destroy the babbitt.

It's cast into place in the block using a mandrel and dam collars, and should be bonded to the cast iron which should be tinned before the bearings are poured. It's then line bored to fit your crankshaft which has been re-surfaced.

Assuming your crank is good and doesn't need grinding, and the bearings are solid and neither cracked, loose or broken (Most I've seen have been loose and cracked) You can test your existing bearings for fit with Plasigage.The ideal clearance is about 0.001 - 0.0015.

If there are shims between the caps and the block you can tighten BUT. if they're really loose, and you remove shims to tighten, you may wind up with a lot of side clearance in the bearing which can also be checked with plastigage.

If there's side clearance, you should "Bed" the crank by scraping the center of both the bearing cap and block half to allow more of the bearing surface to get in contact with the crank. This is an arduous task performed with a bearing scraper and machinist's blue.If the crank isn't "bedded" the adjustment won't last long, and you're likely to have oil leaks out the rear main.

If you have really GOOD babbitt, you could get the crank hard chromed to a larger size and then line bore the bearings to fit.

If you grind your crank to an undersize and don't chrome it back, you'll have to re-pour the bearings since they'll be too big for the crank.

Good quality babbitt contains a fair percentage of tin as opposed to the mostly lead stuff that was used in the '40s because of war rationing.

It's a job best left to a shop skilled in the art.Dallas area folks use Pete's in Albequerque for Babbitt work (There are shops that do it in the area, but none that do it well ask for references).There have been recent postings about other shops.

Bob Carabbio


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