Main bearings Babbitt unusual

Brendan1959

Brendan1959

Member
I pulled down one of my spare motors the main bearings are different to my other motors. Machined groves in the block bearings and none in the caps?
Is this unusual?
 

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Although that is not my favourite way of doing it, I've seen bearings like that go for a long time. It is clear that those are not new bearings and that they haven't been a problem so far. The oil flows around the bearing through that groove till it gets to the join between the block and the cap. You'll notice the edges there are chamfered almost right across the bearing. The oil runs along there so you have lubrication right across the bearing surface. More oil on one side than the other but adequate.
That's fine on the front and middle bearing but I like a spiral groove in the rear one to get the oil across the bearing better.
You can add the groove in the top half now if you like.
 
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Those bearings will work well,oil is carried through the bearing by hydrodynamic theory and the turning crankshaft,the crankshaft is supported by a thin filmof oil,which flows as the crankshaft turns.
 
Brendan,


I can't say that specifically about the A motor. But in the past it was generally thought that there should be a groove in plain slide bearings in order to transport the lubricating oil.

It was later researched that these grooves disrupt the hydrodynamic lubricating film. Therefore, sliding bearings without a groove in it are used nowadays. That's better.

Perhaps because of this someone used more modern bearing caps on your engine?
 
Jim Brierley said:
Looks like that block was set up for full pressure oiling, with a drilled crank for oil to the rods.
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The crank is not drilled, I am hopeful this block can be used with these bearings, its a shame the crank has a little rust and some minor pitting, I think this one was stored outside for a while. I have a couple of cranks, perhaps one can be ground to fit. I only have a vernier, so I have ordered a micrometer so I can measure properly. The last picture of the rear-main almost looks like an insert.
The rods have a similar grove, but in the cap and rod.

Its got one x rod as well.

Jim
I have your book and have read it again while in isolation, a good read.

Brendan
 

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Some minor pitting on the journals won't do any harm. They act as an oil reservoir. The journal and the babbit should never come into contact with each other anyway.
 
After cleaning up the crank i tested with plasti gauge front and center 2 thou, rear about 6 thou.
Block seems standard size ( I have a bore gauge coming).
I have also ordered a Lisle micrometer hone. Apparently they work well and can hone to next oversize.
 

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Over the years, there have been all sorts of screwball ideas about how to improve the dipper tray. That is no doubt one of them. I've even seen holes drilled in the bottom of the tray. I think that was done so that ALL of the oil would be removed when the sump is drained for a service and no old oil will contaminate the new. Pity about the big ends running dry on every start up!:eek:
Who knows what they were thinking. I'd just weld up those holes and use that tray.
 
Brendan1959 said:
Modified dipper pan, I wonder what made them do do this?
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Synchro909 said:
Over the years, there have been all sorts of screwball ideas about how to improve the dipper tray. That is no doubt one of them. I've even seen holes drilled in the bottom of the tray. I think that was done so that ALL of the oil would be removed when the sump is drained for a service and no old oil will contaminate the new. Pity about the big ends running dry on every start up!:eek:
Who knows what they were thinking. I'd just weld up those holes and use that tray.
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Look again. The holes are not affecting the oil levels in the dipper sump. Whatever amount of oil that was in the sump when the engine stopped rotating is the level that would have been there during start-up. Therefore the rods would not have been dry when the engine was started.
 
BRENT in 10-uh-C said:
Look again. The holes are not affecting the oil levels in the dipper sump. Whatever amount of oil that was in the sump when the engine stopped rotating is the level that would have been there during start-up. Therefore the rods would not have been dry when the engine was started.
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Brent, my comment was referring to the example I had just given about holes in the bottom of the dipper tray - not the ones in the picture. With holes in the bottom, the oil drained out very quickly so the rods ran dry till oil filled everything up again.
 
Synchro909 said:
Brent, my comment was referring to the example I had just given about holes in the bottom of the dipper tray - not the ones in the picture. With holes in the bottom, the oil drained out very quickly so the rods ran dry till oil filled everything up again.
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Or they just stopped turning................
 
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