Bronze Model A Ford Rear Main Thrust Plate & Oil Seal installation

[ghalperin]

My thrust clearance quadrupled after a 75 mile drive. It’s about .030 now.
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I picked up this bronze Model A Ford Rear Main Thrust Plate & Oil Seal
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I searched for info on the install, but I haven’t found anything. How do I remove the Babbitt thrust portion of the rear main? I was thinking of just scraping it off with a sharp scraper. There must be a better way.

[J Franklin]

Read here- https://www.fordbarn.com/forum/showt...=bronze+thrust

There was a better step by step pictorial write-up on the barn but I couldn't locate it. Maybe someone else knows where it is hiding.

[ghalperin]

Originally Posted by J Franklin

Read here- https://www.fordbarn.com/forum/showt...=bronze+thrust

There was a better step by step pictorial write-up on the barn but I couldn't locate it. Maybe someone else knows where it is hiding.

Thanks for the link, it’s very helpful.

[ghalperin]

Tonight I pulled the crankshaft and started whittling away. It took about 30 minutes with a breakaway utility knife. It almost looks like the end thrust was poured separately from the main bearing. There’s a dirty section in the center that looks like it was not bonded well with the thrust bearing part.

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Anyways, the bronze part fits perfectly. I’ll check the end play after I get everything cleaned up.

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I’m replacing the rod nuts with ARP nuts. Should I do the same with the main cap nuts?

[Mulletwagon]

Interesting post; please continue the story and photos. Thanks.

[rotorwrench]

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I know this might be a touchy subject but I was curious about who did the babbitt bearing work?

[Dave in MN]

ghalperin,
I have used over 150 of these combination thrust and seal in rebuilding A engines with insert bearings. To avoid a leak, bed the combination thrust and seal with a sealant. Permatex #2 works well.
Good Day!

[ghalperin]

Originally Posted by rotorwrench

I know this might be a touchy subject but I was curious about who did the babbitt bearing work?

The engine was rebuilt in the '70s, I doubt if they're still around. The car was in Napa for decades.

[ghalperin]

Originally Posted by Dave in MN

ghalperin,
I have used over 150 of these combination thrust and seal in rebuilding A engines with insert bearings. To avoid a leak, bed the combination thrust and seal with a sealant. Permatex #2 works well.
Good Day!

Thanks for the tip, I plan on it.

[redmodelt]

When doing new Babbitt, MAKE SURE THE THRUST FACES ARE AS SMOOTH AS THE JOURNAL ON THE CRANK. That means both ends. If they are not will act like a file and remove material same as a file would.

[Nosetime]

Glen, when I put mine back together I used ARP rod nuts and headstuds, like Jim suggests in his book. I also bought the modern sealed main bolt kit from Brattons or Snyders.

[ghalperin]

After completely disassembling, adjusting all the babbett's and reassembling, it still knocked. I sent the rods out to have the wrist pin bushings changed. When I was cleaning it up for reassembly, again, I noticed a small mark on the center of the combustion chambers and matching marks on two pistons. I only had .019" between the piston and the head. I had .020" shaved off the tops of the new pistons and all is good.
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That little tit on the bottom side of the piston was expanding just enough to kiss the head.

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[MikeK]

Originally Posted by ghalperin

. . . There’s a dirty section in the center that looks like it was not bonded well with the thrust bearing part.

That dirty looking section is actually torn apart alloy from internal porosity and shrinkage. Caused by a combination of dissolved gas from a lot of remelt in the heat, overheated alloy resulting in loss of nucleation points, and failure to immediately and properly compact the poured shells by peening after pouring. That caused the thrust face to easily compact in short order when the engine was run.

If it all happened in just a few miles as you state I question the integrity of all three mains, and not just the side faces. If the same guy did the rods you may be in for more problems.

As for your desire to change from stock nuts with cotters to ARP nuts, I'd call that overkill unless you're planning some serious mods and racing.

[ghalperin]

Originally Posted by MikeK

That dirty looking section is actually torn apart alloy from internal porosity and shrinkage. Caused by a combination of dissolved gas from a lot of remelt in the heat, overheated alloy resulting in loss of nucleation points, and failure to immediately and properly compact the poured shells by peening after pouring. That caused the thrust face to easily compact in short order when the engine was run.

If it all happened in just a few miles as you state I question the integrity of all three mains, and not just the side faces. If the same guy did the rods you may be in for more problems.

As for your desire to change from stock nuts with cotters to ARP nuts, I'd call that overkill unless you're planning some serious mods and racing.

Sorry to be misleading in my initial post. The engine has not been apart since the '70s. I was driving it a little too hard on the toll road and afterwards is when I noticed the nocking. All of the babbitt clearances were very close to .0015". I only ended up adjusting a couple.