babbit tolerance? .000?

[BRENT in 10-uh-C]

Originally Posted by Railcarmover

That's my point,time wasn't spent with the knife If a crank didn't spin easy,it was assembled and burnished by spinning on the 'break in stand'.They didn't use shim packs much either,as you say there was one spec, and machines were calibrated regularly.

You mentioned burnished on a break in stand. Do you have evidence of a break-in stand? If you are calling what I have pictured below as a break-in stand, I don't believe that is what this unit was.


Burnishing is accomplished by multiple heat cycles of spinning the crankshaft until the babbitt becomes slightly 'fluid-like' or 'plastic' then allowed to cool. The unit pictured below never spun for long due to there not any engine oil or trans lube in the assembly.


Your comment about them not using shim packs much kinda needs some clarification. First, the shims were specified to be 0.002 - 0.0025 in thickness. Ford did not line-bore the blocks and caps together. The babbitt in the blocks was specified to be bored to 1.623" - 1.624". The caps were specified to be bored to 1.618" - 1.620". The crankshaft main journals were to be ground to 1.622" - 1.624". When the three components were assembled, it effectively had 0.000" tolerances when you do the math, so 'one can assume there was indeed 0.000" clearance requiring burnishing however I have never seen pictures that show this process. To clarify my statement about what Damon said in the video, it is true that at one point in the original machining process where the babbitt did have 0.000" clearance however it did not leave the factory with that clearance. That would be like saying the engine cylinder cases (blocks) were bored to 3.8735" in size. While that is accurate statement, that was not the finished bore size after honing.