Stamping on Crankshaft

[Gene F]

Any one know what this stamp on a crankshaft I had to remove from my Model-A means (for sure)? Looks like a B stamped on it.

 

[oldspert]

Looks more like it is cast more than stamped.
ED

 

[johnneilson]

It sure looks like a B crank reduced to A dims

J

 

[Gene F]

Any one else?

John, that can actually be done? I mean is that practical?

 

[johnneilson]

Gene
Can it be done, yes
Should it be done, I think there are better options to get a counterweight crankshaft
It is an old hot rodding trick to offset grind the B crank rod journals to A dims to increase stroke

If it is within serviceable dimensions continue to run it

John

 

[Dan McEachern]

Looks to be a B crank with removeable counterweights from the picture.

 

[Ray in La Mesa]

Could be a factory remanufactured crank with swegded & pinned weights.

 

[Jim Brierley]

It is what is commonly called a BB crank, turned down to Model A bearing size. The BB cranks came about when someone would send his early B crank to an authorized Ford rebuilder, who would add those weights. I've had engine builders tell me that they'd never seen one of those cranks broken or cracked, because those engines were so smooth. The term BB came about because it was mostly BB truck engines that were rebuilt this way. They worked very well except for racing, I have seen 2 of those engines COMPLETELY destroyed when the pinned on weights came off at high speeds!

 

[Gene F]

Unbreakable...hmmmmmm.

 

[J and M Machine]

Any one else?

John, that can actually be done? I mean is that practical?

Yes because if the rods are already undersize and the crank has been crack inspected then why not?
It could be reground to standard Model A size.
We have done this on the counterweighted C to grind the mains and rods so it would fit into a stock model A.
https://www.jandm-machine.com/grinding.html

 

[Ray in La Mesa]

Had a crank break like that, turns out the balancer had drilled two holes right at the 4th rod journal that reduced the cross section of the journal area to the throw to about 1/2 it's area! It broke at idle.

 

[Hitman]

That looks more like an A crank based on the shoulder near on the rod journal, and the lack of the true BB counterweights which had the overhang on them that require removal to grind the journals.

Better pics would help determine the cause of the break, but it could be the lack of or reduced journal radius.

 

[Gene F]

I know the cause. BJ, at Ron's in Shandon is where I took my engine AFTER this happened. He did not do this!!!!!! As soon as he broke the engine down he called me and told me what happened, and then I went down and he showed me why it snapped. I asked him how many As he has seen break in all the years he has been doing work too.

BJ/Rons did not do this! It was one of the BIG NAME shops that made the mistake.

 

[Hitman]

I don't know "BJ at Ron's in Shandon", so I'm not concerned about that, and didn't see anyone accuse him/them of it.

What was the cause of the broken crank?

 

[Gene F]

I never thought otherwise. I just wanted ot identify the source of diagnosis, and ensure that no blame was their way. Whomever may be reading these comments. I think we agree.

The machining was wrong. Some of the journals were turned with chamford edges, and some were not. When the chamford edges are cut off it creates a weak point, and eventually the shaft will snap. I know it was news to me.

 

[Gene F]

So guys, are these weights easy to get off? Are they even worth saving?

 

[Hitman]

I never thought otherwise. I just wanted ot identify the source of diagnosis, and ensure that no blame was their way. Whomever may be reading these comments. I think we agree.

The machining was wrong. Some of the journals were turned with chamford edges, and some were not. When the chamford edges are cut off it creates a weak point, and eventually the shaft will snap. I know it was news to me.

That's what I suspected and mentioned in an earlier post. It's actually a radius that is supposed to exist at the fillet as it's called. Without it, the crank is weaker there and will likely fail at that point.

 

[Gene F]

Yep. I wasn't even "gettin' on it", and the thing really did not have all that many miles on it. Really, really, really was a bummer for me! You can imagine.

 

[Jim Brierley]

The BB weights are relatively easy to remove. A friend of mine was a welder by trade, he would weld a piece of welding rod to the pins that hold the weights in place, then pull the pin out. He then slid the weight off just enough to grind the rod journals. After grinding them he'd slide them back in place and have the mains ground. A time consuming process but that kept the weight aligned to where they belonged. The crank should be re-balanced afterwards.

 

[Gene F]

I am wondering if I should just take it to recycling. I never have luck selling parts. And when I give a part to a fellow local chapter member I put strings on the part.- they can have it but not as a paper weight on their workbench. It has to go on their car within 60 days or they can walk away from the part.

It still ticks me off the thing was cut wrong, and snapped, A or B. And I sent them a nice crankshaft.