Crankshaft end play

B

bwaii64

Junior Member
I know there's a lot on this around but I'd like to verify before I do something (else) stupid. We've got an early A with cast bearings. The end play is .025". The thrust part of the bearing looks good though we didn't totally remove the bearings. (I don't want to mess more than I have to.)

So... do I
1) leave it
2) break/grind off the rear thrust part of the bearing and put in the brass seal holder with thrust.

If 2, I'm concerned about the thickness of the thrust part. Our cast babbit thrust is about 5/32 and I'm concerned the new brass one won't be any thicker. Anyone know the measurement of that part?

Thanks
Byron
 
I hope someone answers this question as I am curious about the same thing. Does machining have to be done to the rear main cap and block area for the brass to be inserted? Jack
 
I have seen engines run well with as much as 0.13" of crankshaft end play. As crankshaft end play increases, so does oil leakage from the rear main bearing.

I would not do anything in your case. Run it and have fun.
 
I think you have to machine the thrust part to meet your needs. My concern is how much material is available to start with. Is there enough.
 
bwaii64 said:
I know there's a lot on this around but I'd like to verify before I do something (else) stupid. We've got an early A with cast bearings. The end play is .025". The thrust part of the bearing looks good though we didn't totally remove the bearings. (I don't want to mess more than I have to.)

So... do I
1) leave it
2) break/grind off the rear thrust part of the bearing and put in the brass seal holder with thrust.

If 2, I'm concerned about the thickness of the thrust part. Our cast babbit thrust is about 5/32 and I'm concerned the new brass one won't be any thicker. Anyone know the measurement of that part?

Thanks
Byron
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With that much end play it is going to leak a lot of oil. Do you have the engine out? If it was mine I would fix it.
 
We've got 25 thou and you're saying 130 thou ran OK?

I just measured, I've got about another 15 before rod #3 starts touching the piston. It isn't centered.
 
Just measured a brass one, and the thrust face thickness is .110. Call Brattons or Snyders tomorrow and I am sure either would measure what they have in stock for you. They are both good and helpful folks.
 
PC/SR said:
Just measured a brass one, and the thrust face thickness is .110. Call Brattons or Snyders tomorrow and I am sure either would measure what they have in stock for you. They are both good and helpful folks.
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That might not be what it is in the block. The one I got also measured about that also. But the only way to tell for sure is put it in the block.
 
Bob Bidonde said:
I have seen engines run well with as much as 0.13" of crankshaft end play. As crankshaft end play increases, so does oil leakage from the rear main bearing.

I would not do anything in your case. Run it and have fun.
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Unexplained Mysteries:

When I was in High School we had a 31 town sedan with a worn out engine, but it ran fine for playing around town, which is all we did with it. It had more end play than any Model A engine I've ever seen, but did not leak any oil.

When you stepped on the clutch, the pulley and crank went forward about about an eighth of an inch or so, and made a rather loud bang/clunk, but it ran fine, did not pump oil, did not make other running noises, and apparently there was enough room in the rod to piston and front and center main clearances.

I don't recall we ever had the pan off, but I always assumed the babbitt thrust was completely missing on the rear cap and block. Front and center mains must have had enough clearance to the crank as well.
 
For your entertainment:
rearmainblock.jpg
 
forever4 said:
Problem is if previous old time engine rebuilders reground the crank cheeks and widened the journal and just made it up with more babbitt. Then the brass insert might be a little on the small side.
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That is true, it is alsays a crap shoot on these engines. I run into problems all the time where the guy before put the crank in the wrong location. Some guys locate off the old main bores.

We had a block not long ago that had cylinders were bored .020 over. We though this is going to be a good one. The only problem was they were bored on a angle. We only had to go to .080 over to clean it up.
 
George Miller said:
That is true, it is alsays a crap shoot on these engines. I run into problems all the time where the guy before put the crank in the wrong location. Some guys locate off the old main bores.

We had a block not long ago that had cylinders were bored .020 over. We though this is going to be a good one. The only problem was they were bored on a angle. We only had to go to .080 over to clean it up.
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George,
See the note in the lower left. That rearmain bolt hole and the one on the front main were the primary datums for all the crank alignment, cylinder bores, stud hole locations, etc.

ARearMainDetail.jpg
 
forever4 said:
Here is a link to some ideas on locating the bar.
The kwik-way uses the bearing bolt holes.

http://www.fordgarage.com/pages/boringbarfixtures.htm

The K-W bar and block fixture shown can be used with my Lempco to finish semi-finished main caps only, perhaps like what Bill Barlow may do?

Use the K-W fixtures to locate the bar to the block section while in the Lempco frame. They are both 1.25 dia.

http://www.fordgarage.com/pages/lempcoboring.htm
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Thanks for the info. I have a home made boring bar. I use the camshaft bore and pan rail on the front. Ford machined bore for oil slinger seal on the rear. It has always been right on. But I might look into the info from you.
 
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I also had an engine with a lot of end play, and it didn't leak excess oil. I didn't measure the end play, but it was at least .100". I had to tear the engine down due to the center main being shot.
 
Tom Wesenberg said:
I also had an engine with a lot of end play, and it didn't leak excess oil. I didn't measure the end play, but it was at least .100". I had to tear the engine down due to the center main being shot.
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I'm thinking it has to do with the crank moving back and then forward as the engine turns. when the crank comes back at speed past the seal, the oil comes off the crank in to the flywheel. Why does the crank move back and forward. I think it happens when the rods have a slight twist,or some other thing that is not right. If you have a engine that the crank does not do that,it does not leak.
I could be all wrong.
 
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