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Antique Engine Rebuilding (AER)
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When using insert bearings in a Model A engine there has been a problem with spinning the rear bearing. I found a cure.
To fix the problem take the rear upper insert and cut a groove from the front of the oil well on the pass side to back of the well on the driver side. This will give you a hydraulic wedge effect to put oil under the rear main between the shaft and insert. Make sure you do not go beyond the rear oil well, or you will have rear main leak. It is important to put the well from the pass side to the driver side, because of the way the crank turns. It helps the wedge effect.
The problem is it is way to far for the oil to travel from the front of the bearing to the rear. The bearing is 3 inches long. I know this works because I have been doing it this way for some time. If you do not want to do it this way, you will have to leave more clearance, which I do not want to do. I like the .001 per inch rule. it has worked for me for 60 years. Now if you have pressure oiling you will not need to do this. -
Here is the pic from George showing the insert shell. The top pic shows the bearing with the groove , and the bottom one is highlighted to show where it goes.
FullSizeRender.jpgLast edited by Mitch; 06-10-2017, 09:54 AM.Comment
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George has the right idea.
Use inserts unless you happen to know where to get quality babbitt work.
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So how do you tell if you have spun a rear insert? Other than tearing the engine down.Comment
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To fix the problem take the rear upper insert and cut a groove from the front of the oil well on the pass side to back of the well on the driver side. This will give you a hydraulic wedge effect to put oil under the rear main between the shaft and insert. Make sure you do not go beyond the rear oil well, or you will have rear main leak. It is important to put the well from the pass side to the driver...06-04-2017, 12:57 PM -
Note the info corrections to this article starting on post # 30
The following topic covers adjusting the Crankshaft Main Bearing and Connecting Rod Bearing for babbit bearings. This should be a part of your routine maintenance on your babbit engine,performed once every ten thousand miles to insure full bearing life.The following will demonstrate the measurement method using both plastigage...01-15-2018, 06:31 PM -
An automotive engine machinist informed me today that he doesn't believe Model As should run insert bearings because they're not pressurized.
Is this true? What are your experiences with insert bearings in a Model A engine?11-12-2018, 05:27 PM -
Just dropped the sump (looking for the source of an oil leak around the rear main bearing) and found some metal under the baffle at the front that I can’t identify. A couple of the pieces are fairly substantial - the biggest one is around 20mm Long and 5mm thick. Any clues on where to go looking? The engine has been running OK with no odd noises. It has an engine reconditioner label on the side,...You do not have permission to view this gallery.
This gallery has 2 photos.05-26-2018, 12:12 AM -
If you're going to have an engine rebuilt all the way why would you use babbit instead of insert bearings?09-12-2017, 09:59 AM -
My mains on the block side have what looks like drilled 'ports' for babbit to fill..what is the purpose of drilling these "ports"? is it to pin the babbit?...You do not have permission to view this gallery.
This gallery has 1 photos.11-29-2017, 08:21 PM -
My ‘29 motor is at the engine rebuilders after discovering white metal in the sump when chasing a rear main oil leak (see separate thread “Dropped sump, found metal”). He’s going to re-pour the main bearings, but is happy with the condition of the babbit on the con rods (the motor has been rebuilt once that I know of). The babbit on the rear main was mostly gone and what was there looked way...07-08-2018, 11:32 PM
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AFTER PUTTING ABOUT 50 MILES ON MY 29 MODEL A . THE NEXT MORNING I NOTICED A A FAIRLEY LARGE OIL SPOT UNDER THE REAR MAIN . I AM PLANNING ON DROPING THE PAN SOON , ANY THOUGHTS TO WHAT I MIGHT FIND ARE APPRECIATED08-05-2018, 03:56 PM
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I was measuring the rollers of the bearings for least wear. It appears the rollers for the waterpump front bearing should be .25" in diameter.
Some original spiral type bearings had about .002" wear.
A couple of the solid type bearings were about .001"+ wear.
A couple were right on .250".
The older stock new bearins were right on.250"
...10-24-2017, 11:09 PM -
I remember in the past this being brought up and I think it was George Miller that commented one of the bolts holes near the camshaft at the back of the block goes through. Well the last time I forgot to seal that bolt when I put it back together. And yes she was a leaker. I also discovered the hole on the left side above the crankshaft journal goes through. So it's sealer for both of those bolts...07-05-2018, 04:31 AM
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