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Old 05-15-2021, 04:59 PM   #1
PalAl
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Default 28/29 - 30/31 crankshaft difference??

Is there a difference in the 28/29 crankshaft and the 30/31 crankshaft?
28/29 weaker from rod journal to rod journal
30/31 stronger, beefer build in that area??
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Old 05-17-2021, 06:43 AM   #2
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Default Re: 28/29 - 30/31 crankshaft difference??

Other than the very early 1928 beavertail crankshaft I'm not aware of any difference in the later ones
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Old 05-17-2021, 07:57 AM   #3
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Smile Re: 28/29 - 30/31 crankshaft difference??

Beavertail lighter...spools up quicker
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Old 05-17-2021, 10:31 PM   #4
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Default Re: 28/29 - 30/31 crankshaft difference??

Thank you for your input
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Old 05-18-2021, 11:12 AM   #5
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Default Re: 28/29 - 30/31 crankshaft difference??

While the crankshaft being a bit lighter has some affect in inertia, the weight of the flywheel has much more of an affect. With forged steel, the difference in weight is not all that much. I think Ford made the throws a bit heavier to help reduce flex. The early multi-disc clutch & flywheel was lighter than the later single disc type clutch & flywheel,

There were two changes that I'm aware of in the more taper shaped crank throws (beaver tail) of the 1928 shafts but they were in size (diameter) of the round or cheek portion of the throws. Some are smaller ID than others or so I've been told. The difference in weight between the thick throw types and the tapered throw types is less than a pound according to Vince's information on the Ford Garage site.

The counter-weighted cranks are the heavy ones but the counterweights take out some of the natural flex of the early types and that will make the center main last longer. Ford parts were constantly being changed or improved in subtle ways as time went by. Improvements were generally made for reliability of the entire engine assembly.
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Old 05-19-2021, 10:38 PM   #6
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Default Re: 28/29 - 30/31 crankshaft difference??

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Thanks "rotor" good information, I'll also ckeck out the "Ford Garage"
Thanks for the input
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Old 05-19-2021, 10:50 PM   #7
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Default Re: 28/29 - 30/31 crankshaft difference??

I think what Rotor is leading up to are the Model "B" cranks and later.
The "A" was a smaller journal/rod throw then the "B".
Not that some have modified "B" and "C" cranks to fit into the "A" block
John
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Old 05-20-2021, 12:33 PM   #8
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Default Re: 28/29 - 30/31 crankshaft difference??

Some folks add counterweights to the model A crankshafts. The early B engines didn't have the counterweights yet so they vary too. There were different forms of counterweights in the B era as well.

Don't be afraid to use any of the model A crankshafts. Many have pounded pretty hard on the early types and reported little problems with them. Most folks that run them hard are fully aware that something can happen to any of them. The center main is likely going to wear out before the others just because the design only had the one central main journal. Flathead V8s can have the same problems.

The early connecting rods that has the X-shape probably should be retired. I've heard of problems with them.

Last edited by rotorwrench; 05-20-2021 at 12:49 PM.
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Old 05-20-2021, 04:11 PM   #9
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Default Re: 28/29 - 30/31 crankshaft difference??

Quote:
Originally Posted by johnneilson View Post
I think what Rotor is leading up to are the Model "B" cranks and later.
The "A" was a smaller journal/rod throw then the "B".
Not that some have modified "B" and "C" cranks to fit into the "A" block
John
The engine in my coupe is an A block that was modified to accept a B crank, so it has been done.

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Old 05-20-2021, 05:34 PM   #10
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Default Re: 28/29 - 30/31 crankshaft difference??

Rotor is correct in that people, other than Ford added counterweights to the "A" cranks.
Please correct me if this is in-accurate.

The "A" crank was undersize on the mains known early in the program, but still produced.
See Hicks' recounts about the "A".

The "B" crank first produced was without counter weights, very soon after the "BB" added counterweights appeared. Then the "C" version with forged in counterweights.

There are a couple ways to put the "B" crank in the "A" block, I have done the mains to a larger than "A" and used late model bearings. This is stronger to help accommodate cross drilling for full pressure oiling with "B" rods.

All good, John
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