The Ford Barn

MikeK · 02-08-2012, 08:43 AM

Originally Posted by PC/SR
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.

PC/SR-
X patterns on lower (caps) bearings have a negative effect!
Here is Mahle Clevite engineering data to back it up: LINK
If you look at the graphs on the second page, please be aware that the "oil pressure" the 1st graph refers to is developed pressure within the surface film. It has nothing to do with any pump. Nowhere in the entire tech bulletin does it mention anything about pressurized feed!

Oil is not effectively delivered as a film across a bearing by any sharp edged groove, be it circumferential or X pattern. The oil actually pressurizes itself and rolls into a film at a wedge shaped squish area either at the parting line of inserts or from an area of open clearance at the top of a main bearing. That wedge shape is NOT the sharply defined 1/8" relief you see cut into babbitt or made along the edge of inserts. The wedge that delivers oil to an insert is gently tapered clearance not visible to the eye. It is beyond that machined sharp tapered reservoir most people confuse as the actual oil film delivery 'wedge'. It is NOT present on line-bored babbitt, only on properly shaped and engineered shells that have the correct "crush" to achieve this upon assembly. Engineered insert wedge areas actually self-pressurize the oil into the surface film.

Mark:
I'm pretty sure Bill Stipe can make you a 335. He may just not have one on the shelf. The 335 cam + 1.72" intakes + HC head = very peppy highway motor that will still have idle sound like an "A" (use an Aries muffler) and will still idle/parade nicely.

The downside to your madness: You'll have to give up that Nu-Rex centrifugal advance or re-engineer it. Too much total. DO NOT call me on that issue!!! Does Ken have a distributor machine? I gave mine away when I quit racing/building SBC's. The FS ignitions "Zipper" looks like an A dizzy but you can easily tweak the weights/springs/ initial & total adv. to get the curve you need.

02-08-2012, 08:43 AM	#11
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: To Babbit or Not To Babbit vs Inserted?? Originally Posted by PC/SR 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. PC/SR- X patterns on lower (caps) bearings have a negative effect! Here is Mahle Clevite engineering data to back it up: LINK If you look at the graphs on the second page, please be aware that the "oil pressure" the 1st graph refers to is developed pressure within the surface film. It has nothing to do with any pump. Nowhere in the entire tech bulletin does it mention anything about pressurized feed! Oil is not effectively delivered as a film across a bearing by any sharp edged groove, be it circumferential or X pattern. The oil actually pressurizes itself and rolls into a film at a wedge shaped squish area either at the parting line of inserts or from an area of open clearance at the top of a main bearing. That wedge shape is NOT the sharply defined 1/8" relief you see cut into babbitt or made along the edge of inserts. The wedge that delivers oil to an insert is gently tapered clearance not visible to the eye. It is beyond that machined sharp tapered reservoir most people confuse as the actual oil film delivery 'wedge'. It is NOT present on line-bored babbitt, only on properly shaped and engineered shells that have the correct "crush" to achieve this upon assembly. Engineered insert wedge areas actually self-pressurize the oil into the surface film. Mark: I'm pretty sure Bill Stipe can make you a 335. He may just not have one on the shelf. The 335 cam + 1.72" intakes + HC head = very peppy highway motor that will still have idle sound like an "A" (use an Aries muffler) and will still idle/parade nicely. The downside to your madness: You'll have to give up that Nu-Rex centrifugal advance or re-engineer it. Too much total. DO NOT call me on that issue!!! Does Ken have a distributor machine? I gave mine away when I quit racing/building SBC's. The FS ignitions "Zipper" looks like an A dizzy but you can easily tweak the weights/springs/ initial & total adv. to get the curve you need.