The Ford Barn

ppower · 08-04-2015, 01:28 PM

I am rebuilding my Ford model A engine using an engine block from an engine I bought as spare.

The two engines have different crankshafts which seem to be interchangeable. The main difference is the shape of the diagonal webs although the crankshaft with the stouter diagonal webs has circular webs of slightly less thickness.

Can anyone explain the history of the changes?

Rowdy · 08-04-2015, 02:16 PM

Steve Plucker has the info on his website. I believe the change was in mid 28. Yes, they interchange without a problem as the throws and all critical dimensions are the same. Rod

Kurt in NJ · 08-04-2015, 04:45 PM

The thin one is forged , the thicker is cast

John Stone · 08-04-2015, 05:23 PM

Quote:

Originally Posted by Kurt in NJ

The thin one is forged , the thicker is cast

I believe both are forged.

wrndln · 08-04-2015, 05:24 PM

I agree with John, model A crankshafts are forged.
Rusty Nelson

BILL WILLIAMSON · 08-04-2015, 06:08 PM

Sponsored Links (Register now to hide all advertisements)

Should I pop mine out & inspect it?
Bill W.

Tom Wesenberg · 08-04-2015, 07:32 PM

I wouldn't go racing without a counterweighted crankshaft.
In fact I won't even assemble my slow driving engine until I get the counterweights on the crankshaft.

Chuck Sea/Tac · 08-05-2015, 01:21 AM

The thin one one is 28. I hear they flex more. I've been told early racers liked them because of less weight and oil drag?. I have a standard one myself.

ppower · 08-05-2015, 03:55 AM

Many thanks, Presumably the reason for the change has been lost in the mists of time.

Kevin in NJ · 08-05-2015, 05:55 AM

Hard to be sure from the pictures, but it appears to me that the upper crank does not have a proper radius at the corners of the journals.

If that is true then you have to be worried about cracks and it certainly should not be used as is.

johnneilson · 08-05-2015, 10:24 AM

Quote:

Originally Posted by Chuck Sea/Tac

The thin one one is 28. I hear they flex more. I've been told early racers liked them because of less weight and oil drag?. I have a standard one myself.

Yes less MOI to accelerate.
However, what they didn't tell you was that the cranks were changed after just a couple races. The fact of the matter is just how good the machining was for that time.

J

08-04-2015, 02:16 PM	#2
Rowdy BANNED Join Date: May 2010 Location: Gothenburg Nebraska Just off I-80 Posts: 4,893	Re: Two different crankshafts Steve Plucker has the info on his website. I believe the change was in mid 28. Yes, they interchange without a problem as the throws and all critical dimensions are the same. Rod __________________ Do the RIGHT thing - Support the H.A.M.B. Alliance!!!!

08-04-2015, 04:45 PM	#3
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,159	Re: Two different crankshafts The thin one is forged , the thicker is cast

08-04-2015, 05:24 PM	#5
wrndln Senior Member Join Date: May 2010 Location: Lakeville, MN Posts: 5,162	Re: Two different crankshafts I agree with John, model A crankshafts are forged. Rusty Nelson

08-04-2015, 06:08 PM	#6
BILL WILLIAMSON Senior Member Join Date: Dec 2010 Location: FRESNO, CA Posts: 12,560	Re: Two different crankshafts Sponsored Links (Register now to hide all advertisements) Should I pop mine out & inspect it? Bill W. __________________ "THE ASSISTANT GURU OF STUFF"

08-04-2015, 07:32 PM	#7
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Two different crankshafts I wouldn't go racing without a counterweighted crankshaft. In fact I won't even assemble my slow driving engine until I get the counterweights on the crankshaft.

08-05-2015, 01:21 AM	#8
Chuck Sea/Tac Senior Member Join Date: May 2010 Location: Between Seattle & Tacoma Posts: 2,354	Re: Two different crankshafts The thin one one is 28. I hear they flex more. I've been told early racers liked them because of less weight and oil drag?. I have a standard one myself.

08-05-2015, 03:55 AM	#9
ppower Member Join Date: Jul 2015 Location: England Posts: 37	Re: Two different crankshafts Many thanks, Presumably the reason for the change has been lost in the mists of time.

08-05-2015, 05:55 AM	#10
Kevin in NJ Senior Member Join Date: May 2010 Location: South East NJ Posts: 3,398	Re: Two different crankshafts Hard to be sure from the pictures, but it appears to me that the upper crank does not have a proper radius at the corners of the journals. If that is true then you have to be worried about cracks and it certainly should not be used as is.