Centering a Model A Crank, in a Block !

[Kohnke Rebabbitting]

Many a Model A cranks are set off center to the front, and Rear Main, ( Which is most important ) to keep a rear main from leaking, and also time gear mesh in front.


If the crank is off center, as much .010 thousandths, it will cause a leak, you can not fix, with out pouring the Babbitt again, and Align Bore again, this time centering between the Main bolt holes.


On the Model A , Ford used the Left hand rear Main Bolt , on the Drivers side of the car, and gaged ALL their machining Operations off that bolt hole.


The big problem with that, all Align Bore Machines have a Jig, with a set center distance, ( So you get the Gear Mesh Right ) that is used at each end of the block, but while the center distance can be right on, the crank centering, is often not.


An off center crank will leave a gap between the crank, and the Aluminum Seal, and you can't stop oil unless you close the gap.


Even if everything else is right, you have a leaker.


The Factory cranks were always centered, but very few new Babbitt jobs I have seen are.


I have all the jigs sets with my TA-15, A,B,V-8, and Fordson, and none I can use except the V-8, and that I have to use 1 to .005 thousandths of shims, depending on the motor to get the right center distance, but they will center the crank on the V-8"s.


Herm.

[Gary WA]

Nice job!

[Terry Burtz, Calif]

The left hand rear main bolt hole that Herm mentioned was reamed to .505 inch diameter to a depth of 1/2 inch.
From the center of the above hole to the surface of the rear main thrust bearing is specified to be 1.4335/1.4345 inches.
These dimensions are from the Ford drawing of the cylinder block.

[KR500]

Herm, My Kwik Way and Ammco align boring machines pick up off the block main bearing holes, but leave no compensation to acquire the cam centerline to crankshaft centerline distance. I see you like the Tobin Arp set up. Rather than setting up off of false camshaft centerline what would you recommend. The KR Wilson uses a false camshaft bar for the combination machine how do they guarantee proper center to center distance of boring bar frame?

[John Stone]

Along with my normal Kwik Way alignment jigs I came up with this set of jigs to make sure the cam to crank is correct. Only have found one block out of many that the Kwik Way jigs were off but no more than a few thou.

[Mark in MT]

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Excellent work Herm, always a pleasure to see how a real pro does it. My Kwik way lbm uses the jigs that locate off of the main bolt holes. After a clean up cut, I always check the center to center distance to verify it is right. If it is not, I set up a couple dial indicators and move the whole machine straight sideways enough to make the measurement correct on the final cut. A little more work, but it works for me until I can find a TA machine within a thousand miles of home.

[Kohnke Rebabbitting]

Mr. KR, I used a N.O.S. Kwik-Way for about 5 years when I was a Kid. There are many things I can do on a Tobin-Arp, I couldn't do on a Kwik-Way, but the Kwik-Way is the best Align Bore out there if you are doing only Motors. You also have to make sure that the bar is not wore, and the two center springs, and Collar are set to, I think, been a long time, to 1/2 inch compression, for Bar sag.


OK, John, that is what I was talking about, when a set distance jig is used, you are Limited on getting the crank on the center line, and centered in the block. So if you are off by .010 thousandths, which is very easy, your front seal, rear seal, rear shims, and the transmission Pilot shaft, and Pilot bearing will be off.


So, Guys, what I did, on the Kwik-Way, was to center the Boring Bar first, and lock the bar bearings, so it stayed. I have a used Kwik-Way bar, and two Kwik-Way tapered cones, and run it through the cam holes. Then what ever Center distance you use, take that and add half the diameter of each bar to your center distance, and then Mic around each bar and get a feel so the Mic just passes with very light drag.


So, now, with the bar centered, the only direction for adjustment, is up, and down. Now for that adjustment, you use brass shims to go under your Alignment caps, always equal, on both sides of the two Jigs. I have always had to go up, never down.


Another way to center the bar, is make 4 plugs, two for front, and two for the rear. I will try to find some pictures to show what I am talking about. These plugs just fit the holes in the mains with no binding, or looseness. I made mine for T, A, and B's, all in the same plug.


Herm.

[Dodge]

Hi Herm,
Thanks for passing on your experience. I have a Kwik-Way and it has been real good to me. I don't pour my own babbitt I have a few poured at a time and cut them as I need them.
I always like to see how others are doing things. You pick up something each time.
Keep posting.......
Dodge

[bobscogin]

Beautiful!

Bob

[BILL WILLIAMSON]

This helps us understand, WHY some engines don't FARE well & WHY some are constant OIL LEAKERS!
Bill W.

[Kohnke Rebabbitting]

I just realized on the drawing of the plugs, that I don't have the length of the bolt stub shaft, and the " B " dimensions. But these are for a 1/8th inch bar, and Kwik-Way is 1.250, anyway, but you get the idea.


Herm.

[BILL WILLIAMSON]

Everyone is BRILLIANT, in one way or another!
Bill W.

[BRENT in 10-uh-C]

I’m pretty much doing the same as Herm is on my TA-14 except I have converted my machine to use a 1.000” boring bar so I can do Model-Ts too. I locate very similar to Herm’s method with the pins except I have different ones for T's, A's, & B's. Also, I set up a little differently in that I have a modified crank gear for both an A & T that has been bushed down to just slide over my boring bar. I install the camshaft & timing gear I plan to use during the rebuild, and then move the vertical height of the block to be able to set the desired backlash. Next I have a bridge that I made with an indicator mounted into the center that I place over the boring bar at the front main after my lash has been set. I use that bridge with an indicator to measure the set height of the bar, and then use that measurement to set my bar height over the rear main. This ensures the bar is parallel with the block, and as Herm mentioned, the pins locate it side to side.


One other thing I like with the Tobin Arp units (-over the K/W LBM) is their hydraulic drive unit which pushes the bar very smoothly with infinite speed control. Nothing wrong with either set-up, and I know of a gentleman down in Alabama that uses a KR Wilson Boring Plate that he mounts on T blocks and drives the boring bar unit with a T/A drive unit, and it produces some very pretty bearings. I kinda think he may have bored his boring plate from the 15/16" to 1.000" too.







.
.

[Dodge]

Brent, your crank gear idea is brilliant I’m going to make one up also.

Thanks for sharing.

[KR500]

Herm the brass shims makes perfect sense to attain the correct camshaft to crank center to center dimension. I notice you use the Kwik Way kwik clamp bolts. I see you use a Storm Vulcan rod groover also. What depth is usually desired for the tool bit to enter the babbitt? Do you also chamfer the rod oil holes?

[Smitty]

So..my question here is in order for this to work properly the crank would need to have been ground properly....
Herm was saying that if a Model A crankshaft is ground off center it would throw off timing gear mesh and crank centering or would this method compensate for that?
Steve

[BRENT in 10-uh-C]

Originally Posted by Smitty

So..my question here is in order for this to work properly the crank would need to have been ground properly....
Herm was saying that if a Model A crankshaft is ground off center it would throw off timing gear mesh and crank centering or would this method compensate for that?
Steve

Steve, I think what he said was if the crank is "set off center".

As far as grinding off-center, I have a Storm Vulcan 15 grinder that uses centers. I indicate one end off of the surface under the crank gear, and the other off of the rear flange. If the crank is straight, it is difficult to be off if both ends are running true. A crank press is used to straighten one if it is out.

[Smitty]

Brent, What/why would cause a crank be set off center? Herm had mentioned in another post that some shops do not know how to properly grind a Model A crankshaft. This could potentially put the crank off center leading to oil leaks and cam gear mesh issues?
Steve

[Kohnke Rebabbitting]

Two separate Machine operations.


1. Grind the crank to the center line, of the crank.


2. Align Bore the block to the center line, side ways, and up and down. 1. Dead center between the bolt holes, side ways. 2. Up and down with the correct center distance, on both front, and rear main.


Herm.

[Kohnke Rebabbitting]

Pictures, I also have the Hydro-Borer for sale, it was Factory rebuilt in about 1950, and never used, long story!


\Herm