Re: Best Rear Main Seal
 

The Lucky Star,

Thanks for asking for suggestions.

Any machine shop with a large enough metal lathe (something like 16x40) should be able to machine your crankshaft main journals to .015 inch oversize. Then have a crankshaft grinder grind to the specified dimension.

A crankshaft grinder could remove all of the material, but it may or may not be more expensive than taking it to 2 shops.

Regarding the connecting rod journals, your decision to leave them at Model B size is good for strength and fatigue life.

If your donor C crankshaft is not drilled from main to rod journal, you will have no problems when reducing the diameter of the main journals to Model A size. If your donor C crankshaft is drilled with a single hole from rod to main, the hole will break through at the main journal fillet when the main journal is turned down to Model A diameter. If your donor C crankshaft is drilled with multiple passages that are plugged at their ends, you may or may not have a break through problem.

Terry Burtz

Re: Best Rear Main Seal
 

Regarding the C crank, does taking the main journals down to A size affect their hardening?

Re: Best Rear Main Seal
 

The journals are no harder than the remainder of the crankshaft. Reducing them to Model A size won't hurt anything other than reducing the strength of the crankshaft. They don't need to be harder than the Babbitt in the cylinder block.

I don't have the Model B print of the crankshaft, however I am guessing that it is similar to the Model A crankshaft.

I have the Model A crankshaft drawing (A-6303), and the following is the exact wording on the drawing of the heat treatment note.

Heat Treatment
Heat to 1560 deg F. Hold for 30 minutes. Cool to 1200 deg F in 30 minutes. Air cool to room temperature. Brinell 149-179. Center on the 3 main lines bearings & rough machine. Heat 1500 deg F & quench in caustic solution. Anneal at 650 deg F to meet a Brinell of 408-444. Re-anneal front end as indicated (Brinell 302-364). Brinell hardness of flange from 228 to 402-444 as indicated. Finish machine & grind.

Re: Best Rear Main Seal
 

Thank you Terry, much appreciated.

Re: Best Rear Main Seal
 

Terry,
from the sounds of the caustic quench and subsequent anneal it almost sounds as if it is just to harden the surface. I do not know, however, I can tell you from cross drilling a few "C" cranks that the heat treatment is pretty consistent all the way thru the material.


G Baese,
something to keep in mind about using "B" rods in the "A" motor.
The "B" pan has clearance dimples to clear the rod nuts, by using small 12 point nuts on the rods you may not need to clearance the "A" pan.
The slinger and rear thrust ring will more than likely be too large to fit in the "A" rear main cap, check this while crank is in the shop.
Last thing is the fillet radius in the main journals, bigger is better.

John

Re: Best Rear Main Seal
 

My use of an A pan with B rods, is that you WILL have to dimple A pan for clearance...even with use of modern nuts.

Can a fillet radius be too big on a crank ?

Re: Best Rear Main Seal
 

I have an "A" block with a "B" crank and rods. My pan is dimpled.

Re: Best Rear Main Seal
 

I concur with your thoughts John. Several years ago I received couple of aftermarket Model-A crankshafts that apparently were not properly heat treated and failed within a short period with insert bearings. In discussions with the manufacturer this point was mentioned that the hardening process was just on the surface only based on the factory print however in my discussions with others who had drilled original cranks for pressure, their opinion was the original crankshaft hardening went much deeper than just the surface as indicated.

Re: Best Rear Main Seal
 

FWIW,
I too have "worked" on a couple aftermarket cranks.
No more for me.

John

Re: Best Rear Main Seal
 

John, thank you for the great info in post #25.


Geary

Re: Best Rear Main Seal
 

The note on the drawing lists the sequence of manufacturing. After all heat treating, the final sentence of the drawing note reads: Finish machine & grind.

This last operation will remove any hardness on the surface of the journals.