shrink fitting a crankshaft flange

[Dave123]

I am looking at adapting a 4 cylinder Chevy crankshaft into a Ford model T engine.
This is not that rare of a modification to a model T, however including some basic machining to the Chevy crankshaft, it involves adapting a Ford style flange to the rear of the crank to accept the Ford flywheel. Most times the chosen method is to weld the flange in place.
Initially this seems to work OK, but the reports are almost all of these crank at the weld over time. I'm guessing this is due to the stress introduced as a result of welding.
Another method is to shrink fit the flange onto the crankshaft. Apparently this has been successful. The procedure that I was introduced to involved making a flange from 4140 3/4" thick and 4.5" diameter. The crankshaft diameter is 1 7/16"
In this case the machinist used a tapered bore with a corresponding taper on the shaft. Then heated and pressed the flange in place.
From an engineering point of view is a tapered fit stronger than a straight bored fit ?

Dave

 

[Garwood]

I've not seen a tapered shrink fit. I would make it straight.

What is the crankshaft? Nodular iron or Forged 1018 like other Chevy cranks?

Could you just make a new flywheel to fit the gm crank?

 

[jim rozen]

Some motors have a flywheel attached to the rear of the crank with a fairly wide angle taper, and a key. The end of the crank has a tapped hole, and a jesus nut holds the flywheel to the taper. A special puller is needed to extract the flywheel once the nut has been run down to correct torque.

 

[Dave123]

I've not seen a tapered shrink fit. I would make it straight.

What is the crankshaft? Nodular iron or Forged 1018 like other Chevy cranks?

Could you just make a new flywheel to fit the gm crank?

Honestly I’m not sure of the Chevy crankshaft material.
Making a new flywheel would be a big job as the magnets for the magneto are attached along with the pins for the planetary gears

 

[Cole2534]

I've not seen a tapered shrink fit. I would make it straight.

What is the crankshaft? Nodular iron or Forged 1018 like other Chevy cranks?

Are all of Chevy's forged cranks 1018, specifically those in a Gen VI Big Block?

 

[dalmatiangirl61]

Could the Ford flywheel be machined to fit the Chevy crank? How about some pics and dimensions of each?

 

[Garwood]

Are all of Chevy's forged cranks 1018, specifically those in a Gen VI Big Block?

I'm no expert. I had an oe forged 350 crank in an engine. Race engine builder told me chev's typical forgings were just 1018 so not much gaining going on. It held together.

 

[AlfaGTA]

Taper fits on crank output flanges have been used with success for decades.
I have old car experience so my examples might seem unusual, but the point is it has been done without issues.
Bugatti type 57 3 liter straight 8 crank has the flywheel flange and rear main bearing journals mounted to the crank using a taper (long) having a key for clocked location. The end piece is held by a single large nut threaded on to the end of the crank.
These parts are assembled cold just drawing up the taper with the nut.
Disassembly is done by applying 20 + tons of force in the press and then applying quick/large(rosebud toarch) heat to the outside of the female part of the assembly.
I could site further examples but the point is that tapers on cranks works.
Tapers give a better joint than a straight press or shrink, controls runout and parallel fits.
Also makes for better stress distribution, will allow making the OD of the male part bigger at the large end (where the stress concentrates) owing to the taper.
Of course the fit-up is important. Good contact is a must here.
Cheers Ross

 

[sfriedberg]

I don't know from auto engines, but 1018 as a crank material is surprising to me. I expected something stronger and tougher, like 1045 or a low-alloy.

 

[AlfaGTA]

Would like to see the crank.
My solution would be to grind(turn) the Chevy rear main into the taper.
Make your flange to include the rear main journal, tapered internal to the flange. Thread the end of the crank for a pull up/ holding flanged nut bearing in a counter bore below the flange face.
Turn the sleeve section (rear main) oversize. Finish grind all crank journals after fitting flange. Touch off face of flywheel flange while doing the mains to make sure the flange face runs true.
Think I would make this from 4142 pre-hard. Could nitride the part before final assembly if you wish, but I don’t think that would be required

Cheers Ross

 

[Dave123]

Thanks Ross, I do not have the Chevy crank at the shop quite yet, will post a picture or two likely next week.
Due to the lack of room available, the maximum width of the flange can only be about 3/4", even this means having to shorten the rear main bearing (babbit) in the block by 1/2"


Dave

 

[AlfaGTA]

Very familiar with all types of Babbitt mains. Actually allows more flexibility in this case
Could change main OD or position, make new cap for better clearance or rear seal setup.
Advantage in incorporating the rear main into the flange is it will give a longer taper and an overall stiffer connection.
Where is the thrust taken on the “T”?
Cheers Ross

 

[Overland]

I'm having difficulty visualizing this, but would a taper lock style pulley bushing work here ? There's lots of different sizes available.
Bob

 

[EmGo]

I am looking at adapting a 4 cylinder Chevy crankshaft into a Ford model T engine.

Before you go any farther with this, I'd talk to Dan from Oakland. He's been doing model T and A and B stuff for fifty years, has a container full of old cranks outside and a stack of hungry modified cranks under the workbench, counterweighted and stroked and oil-drilled and whatever else you can think of.

I myself would not consider your conversion because it's kind of pointless. There's a lot of other things you can do to a T to make it more fun or faster or reliable or whatever.

 

[Garwood]

There's a lot of other things you can do to a T to make it more fun or faster or reliable or whatever.

I helped build this one.

I'm not sure faster or reliable and Model T go together. Fun- Sure. but not fast or reliable.

 

[farmersamm]

I don't know from auto engines, but 1018 as a crank material is surprising to me. I expected something stronger and tougher, like 1045 or a low-alloy.

I wondered about that too...........................

https://www.azom.com/article.aspx?ArticleID=6115 While it can be forged, and case hardened, it's not the steel of choice for crankshafts........at least from what I can tell.

I'm thinking that "1018" may have been a typo. 1038, from what I can gather, is the OEM grade of steel used. https://www.dropforging.net/how-to-select-materials-for-forged-crankshafts.html

 

[PackardV8]

FWIW, one of the T gurus is here in Spokane and I do work with and for him. He says T horsepower is the most expensive there is. He has built several Montana 500 race winners.
https://themontana500.wordpress.com/
The fun thing is since stock Ts are incapable of exceeding the speed limit on today's highways, they can run an all-out race and hope not to get run over by a minivan in the process.

Interestingly, he's never mentioned the Chevy crank conversion. I'll ask next I'm in there, but since there are readily available forgings which fit?

jack vines

 

[EmGo]

FWIW, one of the T gurus is here in Spokane and I do work with and for him.

Sorry, can't help myself. PM's own Dan is a supplier to the "T gurus". Has also run at Bonneville .... since he's not the type to toot his own horn, someone oughta. Guess I'll volunteer.

Now if he'd just get off the pot with those rear end gears ....

 

[JohnEvans]

If I'm not tearabily mistaken the Chevy crank refered to here is out of a pre 1928 Chevy 4 cylinder. 4 cylinder Chevy and Olds heads were something else grafted on to Ford T blocks.

 

[Dan from Oakland]

Not sure why folks want to put Chevy cranks in a T block, but they do. The stroke is the same as the T crank, so you gain no extra displacement, the crank is made from crappy steel, the front main is the same size as the T crank, the center main is narrower, so you loose bearing area, the Chevy rods have poorly designed big ends- etc. The majority of welded flanges that fall off are due to crappy welds, poor weld prep or an out of alignment pan. A good weld requires almost 100% penetration from both sides, proper preheat and correct filler rod. But yes, there is one fellow who swears by flanges mounted with a taper. Not my cup of tea, but it has been done as Ross stated. Jack- say hi to Tom and Rick for me!