My 1st decent drive of Model A and discussion

[Synchro909]

Originally Posted by M2M

What causes this strain you mention on the main bearing? Apart from counter weighted crank are there other ways to tackle it?

What counter weighted cranks are currently available?

I think just about all of the four cylinder, 3 main bearing engines of the day were weak at the middle main bearing. They were simply under done for the way we drive them today. To improve its longevity, I feel a counter balanced crank is the best (though expensive) option. Prfessure feeding oil to it helps. That puts more oil through the bearing, helping to prevent it getting too warm. Probably the easiest way to look after it is to keep the speed down.
I'm sure others who have played with this longer than I will have more thoughts.

[M2M]

Originally Posted by Synchro909

I think just about all of the four cylinder, 3 main bearing engines of the day were weak at the middle main bearing. They were simply under done for the way we drive them today. To improve its longevity, I feel a counter balanced crank is the best (though expensive) option. Prfessure feeding oil to it helps. That puts more oil through the bearing, helping to prevent it getting too warm. Probably the easiest way to look after it is to keep the speed down.
I'm sure others who have played with this longer than I will have more thoughts.

Give me some figures. How many miles have you done on a rebuilt engine you have installed? Did any of the rebuild engines you fitted to your cars fail? If so, what happened?

[Synchro909]

Originally Posted by M2M

Give me some figures. How many miles have you done on a rebuilt engine you have installed? Did any of the rebuild engines you fitted to your cars fail? If so, what happened?

I have never rebuilt a motor with babbit. All of my engines run on inserts and the middle main bearing is pressure fed by a beefed up oil pump. I've done many tens of thousands of miles on them but I keep my revs down by using the O/D. I travel at 50mph in O/D. That is about the same revs as a standard car would be doing at 40mph. By keeping the revs down to a resonable rate, I have not had a failure and I'm quite happy to leave it that way! The pump is able to maintain 25-6psi to the bearing and I belive it is the extra oil flowing through it that has made it able to last that long.
On some of our long outback trips, one of the guys who uses babbit takes along a rebabbited con rod and middle main bearing cap amongst his spares. I've seen him have to use them.

[M2M]

Originally Posted by Synchro909

I have never rebuilt a motor with babbit. All of my engines run on inserts and the middle main bearing is pressure fed by a beefed up oil pump. I've done many tens of thousands of miles on them but I keep my revs down by using the O/D. I travel at 50mph in O/D. That is about the same revs as a standard car would be doing at 40mph. By keeping the revs down to a resonable rate, I have not had a failure and I'm quite happy to leave it that way! The pump is able to maintain 25-6psi to the bearing and I belive it is the extra oil flowing through it that has made it able to last that long.
On some of our long outback trips, one of the guys who uses babbit takes along a rebabbited con rod and middle main bearing cap amongst his spares. I've seen him have to use them.

Okay, I of course believe you but as with almost all these types of comparisons on this forum what are we actually comparing? Are we comparing your quality insert conversion with a quality babbitt job; or rather, your quality insert conversion with a second or third rate babbitt job?