Scraping white metal bearings

[Bob Culver]

Many homely remedies done in a craftsman manner are entirely satisfactory and will outlive the crank. Bearing loads and rubbing speeds are nothing like moderns. The worn ovality tolerance is more than .001. Any slight ridging can be removed with a fine oil stone and very fine emery paper. Austin cranks are hardly worth grinding and it ruins the vital nitriding on Phoenix. Recondioners are/ were very adept at ruining radii, burning the nitride etc. It has long been recognised that a distinct clearance is the ideal, esp for pressure feed, although in a small dia white metal bearing it can be very small. “Modern” bearings fitted this way often appear as if contact never occurs. When cars ran on dirt roads with splash lube and no air filters wear was significant so desirable to start with minimal clearance. It is very difficult for a reconditoner, even one specialiasing in vintage ware,  to bore big ends for exactly .0005-.001 clearance and a perfect finish, esp when each big end may differ, or may be worn. Hence the hand scraping. The high spots soon reduced giving a small clearance . I am sure i have read the fall by own weight guideline in some older textbook. It seems fine at original Seven speeds , and certainly with a slightly oval crank. It is difficult to maintain a good scraped contact if scraping progresses beyond contact. A sharp whack on the cap dry served to give a final freedom.  My father used to replace main bearings at regular intervals and refitted rods this way and I carried on. ( In my use, with  protracted running at 4000 rpm have noted slight ridging on crankpins, but was running without the top exit holes)
Many caps have been hideously filed. Correction by rubbing on thin fine emery on a piece of plate glass or on a wide fine file plus shims is entirely satisfactory. Many makes were fitted with removable shims. If the outer edge is contoured to match the rod can be located without risk of rubbing on the crankpin, no risk of pieces breaking off, and does not offend the eye!
I have refitted rods from one close size to another and Ford 10 Club members do the same. The difficulty is maintaining the rod square, although with a lathe simple jigs can be made.
As previous when overhauling older cars without filters, it was considered good practice to lightly scrape the bearings. This removed the layer of embedded dirt and reduced the wear rate back to zero. My car was .001 oval at 100,000, sure to outlast the crank, not justifying a filter!