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rotorwrench · 10-22-2020, 05:34 PM

I'm not sure if Ford even peened the bearings after the babbitt was poured into the block. That may have been the purpose of the burnishing process. The crankshaft has a tendency to grow a good bit during that burnishing process due to heat generated. That would have made it problematic to even have the connecting rods attached prior to burnishing since the crank would grow too much and put them in a bind. The growth of the shaft would have been what set the clearance of the bearing and it would have insured the poured bearing would fit the block better since it's not really practical to tin a porous surface like a cast iron block even when new.

A lot of this stuff just wasn't done during rebuilding of engines outside the factory. Peening tools were mostly made for that side of the business in order to get the bearing to fit the block prior to align boring the bearings. Some of those peening tools look better than others for doing that job. There were also expandable rotary burnishing tools that were used by some in the rebuilding business. There was a lot of room for different tooling being used and different ideas about what procedures worked better than others. This leads to a lot of differing opinions on the subject.

All I know is that there weren't a lot of manufacturers doing engine bearings the same way that Ford was. Even Ford dropped babbitt bearing processes with the V8 LB engines in 1936.

This guy mentions the burnishing process in this link.
https://www.kmwford.com/what-is-a-babbitt.html

10-22-2020, 05:34 PM	#23
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,426	Re: Time lapse Model A engine build I'm not sure if Ford even peened the bearings after the babbitt was poured into the block. That may have been the purpose of the burnishing process. The crankshaft has a tendency to grow a good bit during that burnishing process due to heat generated. That would have made it problematic to even have the connecting rods attached prior to burnishing since the crank would grow too much and put them in a bind. The growth of the shaft would have been what set the clearance of the bearing and it would have insured the poured bearing would fit the block better since it's not really practical to tin a porous surface like a cast iron block even when new. A lot of this stuff just wasn't done during rebuilding of engines outside the factory. Peening tools were mostly made for that side of the business in order to get the bearing to fit the block prior to align boring the bearings. Some of those peening tools look better than others for doing that job. There were also expandable rotary burnishing tools that were used by some in the rebuilding business. There was a lot of room for different tooling being used and different ideas about what procedures worked better than others. This leads to a lot of differing opinions on the subject. All I know is that there weren't a lot of manufacturers doing engine bearings the same way that Ford was. Even Ford dropped babbitt bearing processes with the V8 LB engines in 1936. This guy mentions the burnishing process in this link. https://www.kmwford.com/what-is-a-babbitt.html Last edited by rotorwrench; 10-22-2020 at 05:51 PM.