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Old 12-26-2018, 03:51 PM   #1
Terry Burtz, Calif
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Default Worst Rear Main Seal

There was a recent thread on this forum titled "Best Rear Main Seal", It can be found by doing a Google search on:
https://www.fordbarn.com/forum/showthread.php?t=255749

Before reading this new thread, I suggest that members of this forum first read "Best Rear Main Seal" thread to get an understanding of many factors regarding the need for a seal, various seal types and materials, factors regarding seal performance, tolerances, and problems that may happen regarding crankshaft modifications.

In my opinion, the worst design of a rear main seal for a Model A was sold by Ford Parts Obsolete, Long Beach, California in the 1960's, and probably other retailers. I have no idea of who designed the seal, manufactured it, or what rubber compound was used. I also have no firsthand experience.

This (worse design) seal required no modification to the crankshaft to provide a smooth rubbing surface. The seal made contact with the crankshaft on both sides of the rough machined slinger, and fit into the stock oil collection groove. I call it a "pinch" type seal because it pinched the slinger. The only modification required to install this seal was a notch in either the rear main cap or cylinder block to keep the seal from rotating with the crankshaft.

With no smooth rubbing surfaces for this seal to rub against, the heat generated by friction caused the rubber to expand, and this expansion caused the seal to grip tighter on the slinger which resulted in more friction, tighter grip, etc until the resulting failure when the crankshaft and seal welded themselves together and both spun in the collection groove.

Does anyone remember this seal?
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Old 12-26-2018, 04:09 PM   #2
Kurt in NJ
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Default Re: Worst Rear Main Seal

I had one when first putting my car together, didn't use it, several years ago found it--- dropped it and the rubber shattered into many pieces-- made me glad about that decision, still no leaks with stock slinger system
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Old 12-30-2018, 05:18 PM   #3
tuneman
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Default Re: Worst Rear Main Seal

Glad to see your still active on the barn Terry!
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