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PC/SR · 02-07-2012, 11:43 PM

[QUOTE=MikeK;359262]Mark,

My 2c- I wouldn't be the least bit concerned about the misdirected thinking that inserts need a pressurized supply for lube, or the thinking that the oil will only travel half way across the inserts. The primary function of oil pressure is COOLING the inserts. Unless something is seriously wrong, you'll never produce enough oil film loading to generate heat faster than it can conduct through the shells into the block or rods. An A is closer to a lawnmower than a Shelby Cobra.

Circulating oil does cool any bearing, insert or not. But oil's primary purpose is to provide a film to separate the metals so as to reduce friction and heat. The logic of the quote would suggest that no oil is needed at all on a lawnmower or Model A engine.
The problem is not inserts as such, but the circumferential groove. Henry's engineers were not dummies and they did not use circumferential grooves in their unpressurized systems for a reason. They only began the circumferential groove when they began pressure oil.
An unpressuized single circumferential groove simply does not as effectively supply oil across the entire bearing, as the X and longitudinal grooves of the original design do. It is not a coincidence that all modern circumferential grooves are pressurized, and so far as I can find, circumferential grooves "back in the day" were also pressurized.
I would have no problem with unpressurized inserts if the grooves followed the original design.I hope the insert makers will check the science and start putting the X grooves (and parting line reliefs) in unpressurized inserts. Herm has said he thinks they do not because they lack the tools to do so. Maybe that's it. However, the babbit guy I now use made his own tools for making X grooves and he works out of his garage. It would seem like manufacturers would have the resources to make the tools necessary to replicate Ford's design. Maybe just copy the KR Wilson tool, which is a simple design.
That's my 2c.
PS: I got interested in this subject after a 200 mile bearing failure and on teardown found circumferential grooves and no parting line relief. The babbit was otherwise fine. No cracks, flaking, etc. Just excessive wear. That should be added to the body of experience being considered here.

02-07-2012, 11:43 PM	#43
PC/SR Senior Member Join Date: May 2010 Location: Santa Rosa, CA Posts: 1,282	Re: To Babbit or Not To Babbit vs Inserted?? [QUOTE=MikeK;359262]Mark, My 2c- I wouldn't be the least bit concerned about the misdirected thinking that inserts need a pressurized supply for lube, or the thinking that the oil will only travel half way across the inserts. The primary function of oil pressure is COOLING the inserts. Unless something is seriously wrong, you'll never produce enough oil film loading to generate heat faster than it can conduct through the shells into the block or rods. An A is closer to a lawnmower than a Shelby Cobra. Circulating oil does cool any bearing, insert or not. But oil's primary purpose is to provide a film to separate the metals so as to reduce friction and heat. The logic of the quote would suggest that no oil is needed at all on a lawnmower or Model A engine. The problem is not inserts as such, but the circumferential groove. Henry's engineers were not dummies and they did not use circumferential grooves in their unpressurized systems for a reason. They only began the circumferential groove when they began pressure oil. An unpressuized single circumferential groove simply does not as effectively supply oil across the entire bearing, as the X and longitudinal grooves of the original design do. It is not a coincidence that all modern circumferential grooves are pressurized, and so far as I can find, circumferential grooves "back in the day" were also pressurized. I would have no problem with unpressurized inserts if the grooves followed the original design.I hope the insert makers will check the science and start putting the X grooves (and parting line reliefs) in unpressurized inserts. Herm has said he thinks they do not because they lack the tools to do so. Maybe that's it. However, the babbit guy I now use made his own tools for making X grooves and he works out of his garage. It would seem like manufacturers would have the resources to make the tools necessary to replicate Ford's design. Maybe just copy the KR Wilson tool, which is a simple design. That's my 2c. PS: I got interested in this subject after a 200 mile bearing failure and on teardown found circumferential grooves and no parting line relief. The babbit was otherwise fine. No cracks, flaking, etc. Just excessive wear. That should be added to the body of experience being considered here.