Crankshaft crack evaluation?

[Andy Ott]

I'm rebuilding an engine fore my Model T.

its a nice engine with little wear. Standard mains and rod bearings, looks generally like a low mileage engine. 

My problem is that mGnigafluxing reveals a crack as shown in the photo. It is not in the journal area, and is invisible to the eye even with 10x magnification. The crankshaft "rings" without any hint of a problem. 

My question is whether this is a BIG problem or no big deal. I've asked several locals who work on automomobile engines, and get responses all over the field. 

The car is intended to be a locally drivable restoration, with no added power features or intent of long trips or high speed.

any thoughts appreciated. Since it's an engine with little wear overall, I'd like to keep it as original as I can. 

Thanks. 

 

[Matt Harwood]

Well, look at it this way: you spend the money on a fresh engine rebuild and are out enjoying the car when the crank fails, leaving you stranded and in need of a new crank and likely more internal pieces, maybe a new block, plus the expense of another rebuild. You'll have to pull the engine out and put it back in again, reassemble the car, and tune it again. How many months lost? One driving season? Two?

Or you could replace the crank. I have to believe that Model T cranks are plentiful and inexpensive (there are brand new ones available, yes?)

 

This is where other guys chime in and say it's no big deal because it's a Model T and they have low horsepower and the engines turn slowly. They're not wrong, but it's also not their engine and not their money. The real question is: do you feel lucky?

[Mark Simmons]

Well said Matt !  With the availability of all Model "T" or "A" parts it's an unwise move to not replace the crankshaft at this point. This is a case of when not if failure will happen. Better safe than sorry !!!

[cahartley]

Don't chance it....... 

Things like that NEVER get better.

[herm111]

On ‎9‎/‎16‎/‎2017 at 7:15 AM, Andy Ott said:

I'm rebuilding an engine fore my Model T.

its a nice engine with little wear. Standard mains and rod bearings, looks generally like a low mileage engine. 

My problem is that mGnigafluxing reveals a crack as shown in the photo. It is not in the journal area, and is invisible to the eye even with 10x magnification. The crankshaft "rings" without any hint of a problem. 

My question is whether this is a BIG problem or no big deal. I've asked several locals who work on automomobile engines, and get responses all over the field. 

The car is intended to be a locally drivable restoration, with no added power features or intent of long trips or high speed.

any thoughts appreciated. Since it's an engine with little wear overall, I'd like to keep it as original as I can. 

Thanks. 

 

Never install a cracked crank in any thing, like Matt, Mark, and Mr. C said, as what ever started it, will continue. As stated, they never get better.

There is about at least a 60% crack rate in model t cranks, if not more.

I went through a pile of Model T cranks of a good friend of mine,  Mel Alexander, who has passed on now, but there were 135 cranks in the shed, and of them that would grind out to at least .040, I ended up with 25. When I got home, we bead blasted the places they crack, just like yours. and some other places, and out of the 25, I ended up with 6 that were not cracked.

 

Thanks,

 

Herm.

[Larry Schramm]

"If you do not have the time and money to do it right the first time, where will you find the time and money to do it the second time?"

 

I too vote for a new crank.  We were on a tour this summer and one of the Model T's broke a crank.  Trailer time.

[Bloo]

4 hours ago, herm111 said:

Never install a cracked crank in any thing

 

Words to live by.......