Rear Main Thrust Face

Bob Bidonde

Bob Bidonde

Well-known member
I have a low mileage Model "A" engine that has the thrust surface cracked off of its rear main bearing. Using Snyder's A-6334 Rear Main Thrust, is it possible to shave off the residual babbitt thrust face and replace it with a A-6334? Has anyone had success doing this? If anyone has a picture of an installed A-6334, please share it here.
 
I have replaced that thrust with a piece of 1/4" copper tubing, bent and squashed to fit. I did this as a temp cure, don't know how long it would last, but it did what I wanted it to do.
 
I see no reason why it wouldn't work. The rear facing thrust has 2 crescent shaped bronze pieces, one for the forward facing one.
 
i have used the a-6334 brass seal.
the issue i had was excessive crankshaft endplay.

i carefully scored the babbitt rite at the rear edge of the bearing boss then carefully shaved the thrust surface away with a sharp chisel. (i don't know the recommended procedure but it worked for me). then a little file or some sand paper to level it to the block. you can't leave any babbit on that end surface.
once that was done the install is just the same as the OEM seal.
now that you have the seal in there you will have to level the ends to match the block. i did that with a file.
now when you lay the crankshaft in you need to make sure the brass does not interfere with the crankshaft rear main bearing. my crank rubbed on the new seal so i had to remove some brass at the top of the thrust flange to make clearance.
all in all it works great and save me from a rebabbitt job.
i thought i had posted a photo on this forum off it. it may be in a search somewhere.

if i can find the pic i will post it for you.
 
try this

IMG_4876.jpg

https://www.fordbarn.com/forum/showthread.php?t=302623
 
Thanks oldugly. Your photo is what I will do to my engine. Hey Syncro909! Re "You and I have been through a lot of difficult situations and they have all been your fault!" It's tough living on the edge with Model A's! We don't know our limitations!
 
Bob
I seriously doubt that will fix. Fitting and fixing the rear main forward and rear thrust surface is about getting then crankshaft located properly so the entire crank is centered properly and the crank is located properly. What the photo shows is only the upper block retainer with a thrust surface added. How about the front and crank fitted properly. Usually when a thrust surface cracks the bearing surface has as well. You are in need of a rebuild at this point. I’ll bet serious money that when you pull the engine and pull the crank that your bearing surface is probably cracked as well. Although not currently doing Babbitt work, I do Babbitt and line bore and it’s more than you guys think. I think Dave on here does engines so I’d like to see his weight in as well. There’s more to this than you think.

Larry Shepard
 
Larry is right. I have built more babbit engines than I can remember. Anything you do is a band aid at this point. The engine babbit is worn out, Do it right and replace the babbit, machine and balance the crank.
 
Arlyn Bieber said:
Larry is right. I have built more babbit engines than I can remember. Anything you do is a band aid at this point. The engine babbit is worn out, Do it right and replace the babbit, machine and balance the crank.
Click to expand...

By adding counterweights, then balancing it???
 
Bob, I am pouring type 11 Babbitt for another engine. I am using a-6334 rear seal because most of my driving is in the Sierras Nevada mountains. After the babbitt is poured
I line bore it and set the thrust. This is my spare engine for my two 1931's.
Good Luck
Dan
 
if the all the other babbit is good in the block and the caps i see no reason why a guy would have to do a total rebuild on an engine. it is correct that the seal is only only the top part of the thrust but this will not make any difference to the way it locates the crankshaft. the install of this brass thrust surface on my engine set the endplay to .006' with everything still in proper tolerances.
if the cap babbit is good then this repair will keep the car going for years.
this sort of repair (if it had been available) would have been done without hesitation back in the days when these cars were daily drivers.
there are some engines that don't need a total rebuild just because one part has failed.
there are some cars that will never see enough miles to wear out the engine.
there are some folks that can't afford to rebuild/restore
the one i installed worked good. bandage or not it worked fine
 
The engine I want to fix is the original Model A engine from my Coupe. It was rebuilt in the late 1960s, but the builder tied the oil pump in place with cotton clothes line.
Within a few miles of driving the cord disintegrated, clogged the oil pump and the engine starved. I have since replaced this with a Model B in my Coupe, but this A engine has everything good except the cracked thrust face.

I have nothing to loose trying the repair. This Model A engine will not go back into a car. Instead, it will be a play toy on an engine run stand.
 
Bob Bidonde said:
The engine I want to fix is the original Model A engine from my Coupe. It was rebuilt in the late 1960s, but the builder tied the oil pump in place with cotton clothes line.
Within a few miles of driving the cord disintegrated, clogged the oil pump and the engine starved. I have since replaced this with a Model B in my Coupe, but this A engine has everything good except the cracked thrust face.

I have nothing to loose trying the repair. This Model A engine will not go back into a car. Instead, it will be a play toy on an engine run stand.
Click to expand...


that rope trick, sad even mechanics wire would have been better. another hoky fix.
make sure you have some endplay for the crank.
sound like a good project, let us know how it goes. maybe a picture of your finished project.
 
I just did that on a repaired engine that I think someone could get it easy 10 to 15,000 out of before it needs to be completely rebuilt. The problem is they don’t make that thrust washer thick enough it still had .010” play. I ended up laying 55% Silver brazing material on it which brought it Back up to perfect tolerance. I don’t know how long it’ll last, but I would think it should be fine for used engine for someone.
 
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