Quote:
Originally Posted by rotorwrench
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 |
I am not sure that is an accurate statement about the crankshaft growing quite a bit. My experience is that it grows the same as if it were in regular operation. The process of burnishing is to just barely tighten the cap nuts where the cap is barely rubbing. That is enough pressure to burnish the bearing. Since I cannot upload a video here,
CLICK HERE to see if you can open this video that shows what is done, how much cap pressure, etc.
Tinning cast iron does nothing because the tin/solder will not stick to the cast iron. For that reason alone, Ford used holes to anchor the cast bearing to the cast block and or rear main cap.
The reason peening was not done at the factory is because the blocks were brought up to pour temperature in an oven prior to the pour, and were reintroduced into an oven for a slow post cool-down. Just like spin pouring connecting rods, in that production work allows processes for efficiency. Peening is necessary if you cannot keep the block hot enough to keep the cast bearing from prematurely shrinking.