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#4519365 - 09/18/17 11:53 AM main bearing issue
zrxkawboy Offline


Registered: 11/30/04
Posts: 1761
Loc: SD
This is a new one for me, but I haven't rebuilt a large number of engines, so looking for input from the pros. This is a stock rebuild of the 230 flathead 6 in my '57 Plymouth. I checked the bearing clearances with Plastigage, and all clearances look good. However, the Plastigage actually left an impression in the main bearings! Yes, there's an impression in the surface that I can see and actually feel, and it was caused by the Plastigage. I was really surprised, as I've never seen this before. The rod bearings did not do this.

I had ordered the bearings (and most other parts) from Falcon Global. Everything else was name-brand, but the bearings were in a plain package with no print, save a hand-written part # and size.

Opinions, please...thanks!
_________________________
"Think of all the Ford owners who will someday want an automobile." John Dodge


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#4519374 - 09/18/17 12:01 PM Re: main bearing issue [Re: zrxkawboy]
440Magnum Offline


Registered: 02/01/09
Posts: 8754
Loc: Texas
The old flatheads might have originally spec'd pretty soft bearings with a lot of capacity to safely embed small particles, since the oil filters were partial-flow and oil was pretty poor back then. I'm a little surprised they were THAT soft, though, given that the Plymouth engines did have full pressure lubrication all the way back to the early 1930s, unlike GM.

Its been many years since I fooled with a Chrysler or Plymouth flathead, so I can't honestly tell you that I remember that level of softness one way or the other. I think I'd be inclined to try to find a set of more name-brand main bearings and compare before I risked running those.
_________________________
'66 Dodge Polara & '69 Dodge Coronet R/T both 440/727
'08 Ram 1500 4.7/545RFE
'12 Challenger SRT8 392/6-speed
'99 XJ 4x4 4.0/AX15, '14 WK2 4x4 3.6/8HP

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#4519383 - 09/18/17 12:14 PM Re: main bearing issue [Re: zrxkawboy]
Oldmoparguy1 Offline


Registered: 01/21/05
Posts: 5613
Loc: Charlotte, NC
Originally Posted By: zrxkawboy
This is a new one for me, but I haven't rebuilt a large number of engines, so looking for input from the pros. This is a stock rebuild of the 230 flathead 6 in my '57 Plymouth. I checked the bearing clearances with Plastigage, and all clearances look good. However, the Plastigage actually left an impression in the main bearings! Yes, there's an impression in the surface that I can see and actually feel, and it was caused by the Plastigage. I was really surprised, as I've never seen this before. The rod bearings did not do this.

I had ordered the bearings (and most other parts) from Falcon Global. Everything else was name-brand, but the bearings were in a plain package with no print, save a hand-written part # and size.

Opinions, please...thanks!

Are you sure you have the right bearings? A 57 should be new enough to use tri-metal bearings.
_________________________
A Randomly Selected Thought For The Day:
If Noah had used Zip, he could have used a smaller boat.

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#4520785 - 09/19/17 10:43 PM Re: main bearing issue [Re: zrxkawboy]
zrxkawboy Offline


Registered: 11/30/04
Posts: 1761
Loc: SD
Update: I showed one of the bearings to my machinist. He said he had seen this before and as long as the crank spins fine after assembly, he wouldn't hesitate to run them. Not what I expected to hear, but he's always done good work for me and given me sound advice.
_________________________
"Think of all the Ford owners who will someday want an automobile." John Dodge


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