thoughts on main bearing Babbitt ??
 

i have a block that i am going to have the main bearings re-babbitted.

the question is -- when they do the babbitt should they spiral groove the bearings or should i ask them not to?

there was some discussion about this a while back. every model A engine that i have taken apart has had the groove cut in. and the last engine i had babbitted was grooved.

thank you
ou

Re: thoughts on main bearing Babbitt ??
 

I can give you my builder's thoughts as I am not an expert mechanic but he is. Grooved. Also, just along related lines Babbitt is sufficient for up to 5.5 head if you're going that route. Rod bearings absorb more in general terms.

Good luck with it!

Re: thoughts on main bearing Babbitt ??
 

If you’re taking it to somebody to pour Babbitt, and the guy you’re taking it to doesn’t have his own (strong) opinion about what shape of oil groove performs best with gravity feed oiling in a internal combustion engine, I’d be a little worried.

Re: thoughts on main bearing Babbitt ??
 

Whomever you are talking to will hopefully have experience and a track record to stand behind whatever they do. Telling the babbitter what to do generally is not a good idea. Most do what's been done before. I studied bearings, lubrication, and the evolution of plain bearings and came to different conclusions which are not main stream but I know work just fine!

Re: thoughts on main bearing Babbitt ??
 

I strongly agree with this!!!

Re: thoughts on main bearing Babbitt ??
 

The groove needs to be there to supply oil evenly across surface of bearing and crank along with oil wells.
Ford did everything for a reason and if it wasn't needed he wouldn't of done so.
https://www.jandm-machine.com/rebabbiting.html

Re: thoughts on main bearing Babbitt ??
 

nice!

Re: thoughts on main bearing Babbitt ??
 

Damn nice.

Re: thoughts on main bearing Babbitt ??
 

Your babbit work is absolutely STUNNING!!!

Re: thoughts on main bearing Babbitt ??
 

The most plausible alternative design I've seen involves a shallow circumferential groove (straight across) at the top of the bearing where the oil enters via a hole leading to the valve chamber. This groove serves to distribute oil to chamfers at the parting lines on either side of the bearing. Oil accumulates in these chamfered areas and then is pulled into the slipstream of oil coating the journal as it rotates. There are no grooves on the bottom half of the bearing (other than the side chamfers) in order to maximize surface area.

Many insert bearings use this groove design. I've heard the argument that this design is inappropriate for gravity-fed oiling systems, but I haven't heard a satisfactory explanation as to why that would be.

Re: thoughts on main bearing Babbitt ??
 

I think this discussion has been going around forever.About 20 years ago I was in the shop of the guy that used to do my babbitt,(long since passed) and he and another customer were discussing this.The customer had all kinds of theories,opinions,articles,and probably anything published on it from the last 50 years.The man was very thorough,and presented it all very well,and when he was done George told him,I will pour it any way you would like,but the only one I will stand behind is the way I do it.

Re: thoughts on main bearing Babbitt ??
 

That's because every engine builder has exactly one feedback loop: comebacks. If he pours bearings a certain way, and nobody brings those bearings back having failed, then the design is good. If he tries something new and has to do a warranty repair later, the design is bad. That's as deep as the thinking goes.

Re: thoughts on main bearing Babbitt ??
 

I've seen main bearings done with no grooves in the cap and rod bearings with none in the top end of the bearing. There were grooves on the other side of them and chamfers along the join line. That makes sense to me because I think the hydrostatic wedge on which the crank shaft and rods ride is uninterrupted and at its strongest where it is needed. Just to be safe and get enough oil through the bearing, the owner ran low viscosity oil. From memory, about 10 or 15W30.
What do others think?

Re: thoughts on main bearing Babbitt ??
 

Not going to argue with anyone. A groove across the face/ load side of the bearing is a BAD idea that disappeared for the most part in the 30s with a few notable acceptions. Cutting the grooves the way Ford did is the safe way if you don't want to argue with all the Ford experts that are monkey see monkey do. If you studied how plain bearings actually work you would come to the same conclusion. NO grooves in the main caps. The crank will be supported by the oil wedge period. A short longitude groove in the block side will assure sufficient oil makes it onto the bearing surface. If you leave a space for oil it will go there. For A and B rods annular grooves are all you need just like millions of other babbitted rods. I am not trying to change anyone's mind but I know what I know and I know what works.

Re: thoughts on main bearing Babbitt ??
 

I stand with Richard Knight on this one. The oil wedge generated by the turning of the journal is hundreds of psi. A groove just kills this high pressure.

Re: thoughts on main bearing Babbitt ??
 

I agree as well. Anything that disrupts that hydrodynamic wedge of oil is nonproductive.

Re: thoughts on main bearing Babbitt ??
 

Steve, using a cast bearing for up to a 5½:1 compression head is a myth that started in the Model-A community many, many years ago however it was one of those 'Monkey See, Monkey Do' or 'He said, She said' pieces of advice. One of the modern-era high compression heads that were retrofitted onto restored Model-As was the Larry Brumfield head that was 5.9:1 compression at stock bore and stock head gasket thickness. Most overbores and modern head gaskets increased the compression ratios to 6:1 or greater. These engines lived with only cast bearings, and many of us have reliably used cast bearings on 8:1 compression heads. Diesel engines successfully used cast bearings for their early years with compression ratios hovering around 3X the 5.5 CR number.

I am not going to argue with Richard over this but John's picture showing the groove in the Cap is not a deal-breaker IMO. Look at several things regarding the Cap. The cast bearing has been poured onto a tinned Cap which creates a bond that would hold the Babbitt material firmly to the Cap even if the groove separated the two sections of the bearing material. So there is not any issue as long as the Cap has been properly poured.

Secondly, any additional flow of oil that can additionally coat the journal pin will prevent wear and add longevity over a Cap not having that channel to allow oil to flow. Oil is always going to be your friend.

Thirdly, things have changed regarding RA finishes on Crankshaft journal pins. If the RA (-average surface roughness) finish is low enough, you have less wear of the softer cast bearing material. Think of a file surface. The teeth of a file will carry more oil however the aggressive teeth will create a faster wear of the surface it rubbed against. The composition of grinding wheels we are using on our Crankshaft Grinders has hugely improved over the past 2-3 decades. Also, I am using leather belts to finish polishing the journals instead of the old abrasion belts. I strive for a micropolished RA finish of under 0.5 on the pins, which is much superior to what we say 25 years ago. With that said, the "teeth" do not rotate the same amount of oil as they did when Crankshafts were originally manufactured. Therefore the groove is of much greater importance than some might think.

Re: thoughts on main bearing Babbitt ??
 

This is still a good discussion. The key here is understanding and believing that interrupting the oil film is a bad idea. This is really undisputable but still not understood by many. Some folks seem to think model A bearings are special or unique, they are not, they are "plain" bearings also known as friction bearings. Babbitted early V8s did away with the elliptical grooves going to transverse and annular type of groove. My own B with the brumfield 5.9 head, downdraft, and other mods has no grooves in the main caps, annular grooves in the rods and No shims is probably still running down in texas as I sold that car in 2010. My major point is directed to the folks who say that won't work. Well if that were true then why are there millions if not billions of plane bearings in virtually all automotive engines that seem to work just fine.

Re: thoughts on main bearing Babbitt ??
 

its going for babbitt at the end of june.
i like both sides of this discussion. i think once it is in the babbitt guru's hands i get whatever he gives back to me and run it. i can not question his work unless it fails.
the other way i look at it is, this car will never see more that a couple hundred miles a year. it will outlast me.
thank you all for helping

Re: thoughts on main bearing Babbitt ??
 

Rick, your comments are very confusing to understand. For example, you said "The key here is understanding and believing that interrupting the oil film is a bad idea." I struggle understanding the meaning of your statement. The second part of this is, who made that statement that someone is interrupting the oil film?? :rolleyes: :o

Your second comment says "Some folks seem to think model A bearings are special or unique, they are not, they are "plain" bearings also known as friction bearings. ". Where does this comment come from?

From my vantage point (-and by views of many) Model-A Bearings ARE "unique", ...and ARE "special" when compared to other internal combustion engines found in service today.

The first thing that makes them unique compared amongst other types of friction bearings in use today is they are a cast (-or casted) Bearing. Secondly, they are a 'special' bearing in that it is a specialized process to fabricate them correctly. One other key trait that Model-A bearings have over other bearings such as your Model-B or the referenced Early V-8 engine bearings is the lack of pressurized oil to lubricate the Main Bearings. Transverse oil grooves do well when pump pressure is moving the oil within the grooves. Alternatively, not so well on lubrication systems relying solely on head-pressure to move the oil. And, -especially when that film of oil is introduced on the upper side of the Bearing where there is not a force from the piston's pressure however maintaining a moving film of oil on the Cap side where the Bearing to Journal Pin clearance is less and lacks the ability of the oil to distribute evenly. (Hence the reason for the particular design of the Bearing's oil groove on a Model-A engine ...which is different than the design found on later pressurized oiling systems. ;) )