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Old 10-20-2020, 11:24 AM   #18
BRENT in 10-uh-C
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Join Date: May 2010
Location: Eastern Tennessee
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Default Re: Time lapse Model A engine build

Quote:
Originally Posted by rotorwrench View Post
Ford turned their engines with large electric motors to bed them in. The motor circuit had a large amp meter that employees on the run in line would monitor to make sure that the current dropped to a specific range of amps that indicated that the engine was indeed ready for service and could be sent on to the different assembly lines there and around the country. This also gave them a chance to check for coolant system leaks and lubrication system function & leakage. If an engine took too many amps to turn or not enough then it was set aside for further repair evaluation.

I don't know how tight they were to start or what was considered acceptable but they undoubtedly had limitations to go by.

Most rebuilders set them up to where they can be started and run on a test stand to insure a unit will work for the customer. I'd say it was set up tighter than what most rebuilders would consider as normal if the starter wouldn't turn it over. Lubricant has to have a clearance to do it's job. The clearance should not have to be "opened up" by turning a crank in a too tight no clearance situation. The clearance can be kept to a minimum if proper machining practices are followed. Bedding in processes should smooth out minute high spots in a bearing surface rather than actually opening up a clearance that was not there to begin with.

I've seen so many reality TV productions that just have to add drama that I tend to avoid them like the plague whether they are about cars, motorcycles, or just life in general.
I am going to add something that many do not understand about this process. When most crankshaft grinders resize a crankshaft, we are using a process call plunge grinding. Unlike a cylindrical grinder, we engage the grinder stone to the journal pin coming in 90 perpendicular, and once we have achieved the target size, we move the carriage over to the adjacent area of the pin and grind that to size. Although the quality of tooling has been improved over the years, the ability to make both cuts on the same journal equal the same number is beyond difficult at best. For my personal machine, if I can replicate a grind to a quarter-thousandth (0.00025"), then I am happy. Even if you hit the differential at a half-thousandth, your eye will see a faint line difference however your fingernail will likely never detect it. This differential is usually camouflaged by using a cork belt to blend the differences in sizing. So when the cast bearing is heated due to friction, it tends to become fluid in the tight areas and flows towards the looser clearanced areas. It really is not over-tightened as the clearances are probably around 0.00075" to 0.001" in certain areas. There is still oil clearance in the adjacent areas around the journal pin.
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