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03-14-2024, 12:23 PM | #1 |
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Join Date: Dec 2014
Location: Hillsboro IL
Posts: 479
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cracked main bearing
This is the rear main bearing cap o a 29 I am working on. Is there anyway to save this or is it new babbit time?
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03-14-2024, 03:26 PM | #2 |
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Location: SoCal
Posts: 592
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Re: cracked main bearing
Those flaws look like they have been there since it was poured.
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03-14-2024, 03:49 PM | #3 |
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Join Date: Jan 2012
Location: Western North Carolina
Posts: 3,913
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Re: cracked main bearing
The prudent thing to do is to find a good cap and then fit it to the crankshaft using Timesaver. You could put it back in but you are taking a chance. If you only drive the car occasionally down to the local ice cream store then you could chance it. Don't put it back in if you plan on doing any tours or extended trips.
It looks like you have the engine out of the car and have it mostly apart. If you haven't already done so, take the crankshaft out and look at the Babbett in the block.
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A is for apple, green as the sky. Step on the gas, for tomorrow I die. Forget the brakes, they really don't work. The clutch always sticks, and starts with a jerk. My car grows red hair, and flies through the air. Driving's a blast, a blast from the past. |
03-15-2024, 10:16 AM | #4 |
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Location: Long Island, NY
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Re: cracked main bearing
The crack is likely due to the Babbitt rear thrust face not adhering to the cap when it was poured, so there is a small gap between the Babbitt and the cap. Continuous on-off pressure from the crankshaft bends the Babbitt and it eventually cracks. This is a common malady with the Model A's rear main bearing.
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Bob Bidonde |
03-15-2024, 01:01 PM | #5 |
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Location: Ohio
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Re: cracked main bearing
These responses look spot-on to me.
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03-15-2024, 03:36 PM | #6 |
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Re: cracked main bearing
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SAJ in NZ |
03-16-2024, 12:17 PM | #7 |
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Join Date: May 2010
Location: Long Island, NY
Posts: 3,486
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Re: cracked main bearing
The repair thrust face available from Syner's (A-6334) is my choice. I have an engine that needs it. I plan to secure the repair thrust face with JB Weld.
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Bob Bidonde |
03-16-2024, 02:51 PM | #8 | |
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Location: Campbell,CA, USA
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Re: cracked main bearing
Quote:
The rear thrust bearing is loaded by timing gear thrust and when the clutch pedal is depressed. The forward thrust bearing is not loaded and simply keeps the crankshaft from moving. My suggestion is to do nothing because there is a forward thrust bearing in the cylinder block that will keep the crankshaft from moving. |
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