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Old 10-19-2020, 09:26 AM   #9
BRENT in 10-uh-C
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Join Date: May 2010
Location: Eastern Tennessee
Posts: 9,731
Default Re: Time lapse Model A engine build

Quote:
Originally Posted by alexiskai View Post
If you search for "Hagerty" on previous forum posts you'll find a multi-page argument about the bearing clearance choices made by the engine rebuilder they hired to do the babbitt. Tight bearings is the reason for the tow start.
I have participated on Fordbarn for better than 20 years or so, and this has always been a topic of discussion. Originally when Ford authorized shops did the rebuild, they used a large burnishing machine to 'fluidize' the cast bearing material so it would conform to the journal pins. Fast forwarding to modern-era rebuilders, most must compete on a price-point which does not allow the extra time for them to burnish bearings. The alternatives at that point are to set them bearing clearance up looser so the starter can rotate the engine, -or set the clearances tighter requiring mechanical assisted starting until the engine has self-burnished the bearing. Part of the issue is if the bearing clearances are left loose enough to rotate freely, as the engine breaks-in the clearances becomes excessive creating noises the car owner complains about. Since most do not wish to adjust (tighten) the clearances themselves, it is easier for the engine rebuilder to set-up the engine tighter to alleviate the need for adjustment within 500-1000 miles.
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