The Ford Barn

Afordman31 · 03-27-2016, 06:43 PM

Checking the end thrust on a block I am planning to put together.
Les Andrews states the maximum of .003 thousands. I have .016 using a dial indicator. Snyders sells a rear main thrust made of Bronze if the babbit is cracked. Mine is in pretty good condition. My question is will the original type oil seal that Snyders sells close up the thrust. Included are pictures of my rear main and the seal pictures taken from Snyders catalog. Thank you

Ron W · 03-27-2016, 07:03 PM

You can't use the rear main thrust bronze without removing the babbit. If it were mine I would leave it till the motor needed a rebuild for other reasons. Other opinions may vary. Ron W

40 Deluxe · 03-27-2016, 07:28 PM

These comments on crankshaft thrust reminded me of reading about the Model A powered Pietenpol homebuilt airplane of the 1930's. He (Pietenpol) said the stock bearing thrust setup was OK to handle the thrust of the prop! Think of it: That 'A' running at or near full throttle to get airborne and stay in the air, the propeller pulling against that small thrust surface to keep the plane flying. Does anybody know how many hours between overhaul that Babbitt was good for? How often did failures occur?

Dodge · 03-27-2016, 07:52 PM

I might get barked at here, but I had a motor with very good Babbitt and the thrust was worn like yours. I took solder and built up the thrust surface on the front side of the cap
And machined it flat until I got the proper thrust. 12 yrs. running and still good trust clearance.
I used a Dillon torch that puts a concentrated heat to the Babbitt and only puddles a small section at a time almost like tig welding.
My solution..
I grabbed some babbit shavings the last time I had a block done in case I ever have to do this again.

PC/SR · 03-27-2016, 08:31 PM

Ran into the same problem once. Whether the bronze is going to take up the clearance depends on whether the front or the rear babbitt is worn. Check the thickness of the existing rear thrust babbitt and compare it to the thickness of the bronze. If the bronze is thicker, try it.
If it is the front that is worn, the bronze in the rear is not going to solve the problem, though it may take any abuse from excess clearance better without cracking the remaining babbitt.
Or just run it. Factory specs are .003-.008 clearance. I know a guy who runs his at .013-.014 for a long time no problem. Just be sure there is sufficient clearance on each side of the small end of the rod between the rod end and the piston.
Of course, be very careful removing the rear thrust surface. I would use a Demel tool with a small straight cutter.
Dodge's idea of building up the front is a good one and good to know it can be done, but I am not sure I would have the nerve to do it, and do not have the machining tools to do that. But beats a whole new babbitt job and that is what you would do anyway if you do screw it up.
There are threads on this in the Search feature and some have tried it and it works.

colin1928 · 03-27-2016, 08:54 PM

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Minimum 0.003"

George Miller · 03-27-2016, 09:14 PM

.016 is going to leak lots of oil. The bronze will work if the babbitt was machined in the right place last time it was done. The front babbitt does not wear much, the load is on the rear from the pressure to release the clutch. I would try the bronze what do you have to loose. If it is to tight you could scrape the front bearing to fit.

I have used a few of the bronze thrust bearings they work fine.

Synchro909 · 03-28-2016, 04:39 AM

If the bronze thrust doesn't take up enough of the end play, you could try tinning the bronze face - maybe even "dabble" at bit more on it. Ordinary solder should last a long time but a little babbit would be better. File / scrape to get the end play you want. I aim for 4 to 6 thou.

Bruce_MO · 03-28-2016, 12:53 PM

I have a Coupe with about 0.015" clearance (you can see the crank pulley move forward when you blip the throttle). It's been that way for a pretty long time and it doesn't leak any oil. I'll leave it alone until a full rebuild is needed. But I suppose if I had it apart, I would deal with it with the best possible/lowest risk of failure fix.

Good luck with whatever you choose.

03-27-2016, 07:03 PM	#2
Ron W Senior Member Join Date: Jan 2011 Location: Central Me. Posts: 260	Re: Crank Shaft End Thrust Question? You can't use the rear main thrust bronze without removing the babbit. If it were mine I would leave it till the motor needed a rebuild for other reasons. Other opinions may vary. Ron W

03-27-2016, 07:28 PM	#3
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,778	Re: Crank Shaft End Thrust Question? These comments on crankshaft thrust reminded me of reading about the Model A powered Pietenpol homebuilt airplane of the 1930's. He (Pietenpol) said the stock bearing thrust setup was OK to handle the thrust of the prop! Think of it: That 'A' running at or near full throttle to get airborne and stay in the air, the propeller pulling against that small thrust surface to keep the plane flying. Does anybody know how many hours between overhaul that Babbitt was good for? How often did failures occur?

03-27-2016, 07:52 PM	#4
Dodge Senior Member Join Date: Nov 2011 Location: Sonoma, CA. Posts: 1,496	Re: Crank Shaft End Thrust Question? I might get barked at here, but I had a motor with very good Babbitt and the thrust was worn like yours. I took solder and built up the thrust surface on the front side of the cap And machined it flat until I got the proper thrust. 12 yrs. running and still good trust clearance. I used a Dillon torch that puts a concentrated heat to the Babbitt and only puddles a small section at a time almost like tig welding. My solution.. I grabbed some babbit shavings the last time I had a block done in case I ever have to do this again.

03-27-2016, 08:31 PM	#5
PC/SR Senior Member Join Date: May 2010 Location: Santa Rosa, CA Posts: 1,278	Re: Crank Shaft End Thrust Question? Ran into the same problem once. Whether the bronze is going to take up the clearance depends on whether the front or the rear babbitt is worn. Check the thickness of the existing rear thrust babbitt and compare it to the thickness of the bronze. If the bronze is thicker, try it. If it is the front that is worn, the bronze in the rear is not going to solve the problem, though it may take any abuse from excess clearance better without cracking the remaining babbitt. Or just run it. Factory specs are .003-.008 clearance. I know a guy who runs his at .013-.014 for a long time no problem. Just be sure there is sufficient clearance on each side of the small end of the rod between the rod end and the piston. Of course, be very careful removing the rear thrust surface. I would use a Demel tool with a small straight cutter. Dodge's idea of building up the front is a good one and good to know it can be done, but I am not sure I would have the nerve to do it, and do not have the machining tools to do that. But beats a whole new babbitt job and that is what you would do anyway if you do screw it up. There are threads on this in the Search feature and some have tried it and it works.

03-27-2016, 08:54 PM	#6
colin1928 Senior Member Join Date: Mar 2013 Location: Australa Melbourne Posts: 878	Re: Crank Shaft End Thrust Question? Sponsored Links (Register now to hide all advertisements) Minimum 0.003"

03-27-2016, 09:14 PM	#7
George Miller Senior Member Join Date: May 2010 Location: NC Posts: 2,975	Re: Crank Shaft End Thrust Question? .016 is going to leak lots of oil. The bronze will work if the babbitt was machined in the right place last time it was done. The front babbitt does not wear much, the load is on the rear from the pressure to release the clutch. I would try the bronze what do you have to loose. If it is to tight you could scrape the front bearing to fit. I have used a few of the bronze thrust bearings they work fine.

03-28-2016, 04:39 AM	#8
Synchro909 Senior Member Join Date: Jun 2014 Location: Melbourne, Australia Posts: 7,496	Re: Crank Shaft End Thrust Question? If the bronze thrust doesn't take up enough of the end play, you could try tinning the bronze face - maybe even "dabble" at bit more on it. Ordinary solder should last a long time but a little babbit would be better. File / scrape to get the end play you want. I aim for 4 to 6 thou. __________________ I'm part of the only ever generation with an analogue childhood and a digital adulthood.

03-28-2016, 12:53 PM	#9
Bruce_MO Senior Member Join Date: May 2010 Posts: 433	Re: Crank Shaft End Thrust Question? I have a Coupe with about 0.015" clearance (you can see the crank pulley move forward when you blip the throttle). It's been that way for a pretty long time and it doesn't leak any oil. I'll leave it alone until a full rebuild is needed. But I suppose if I had it apart, I would deal with it with the best possible/lowest risk of failure fix. Good luck with whatever you choose.