I've adopted a fully inserted "rebuilt" motor. The previous owner gave up on it in lieu of a v8. It was making a strange noise which turned out to be #4 piston hitting gasket. Upon tear down -It appears to have actually been rebuilt recently. Very clean with all new components. .125 over bore. I tore it down to check everything. I noticed that with all pistons and rods removed it has about .020 of end play- perhaps even more. It wasn't leaking oil but seems to be too much end play. Thoughts on this as well as a potential remedy is appreciated. It's a counter balanced crank as well.
Crank shaft end play
- Thread starter Towd56
- Start date
Synchro909
Well-known member
20 thou is too much end play. I adjusted excessive end play by putting some babbit on the thrust ring that stops the shaft going too far back, thus leaving the whole bronze ring for the main thrust face. With a little careful fitting, you'll get it spot on.
Another option might be to put about 15 thou packing under the same bronze "crescent". It is trapped in there so can't come adrift.
Another option might be to put about 15 thou packing under the same bronze "crescent". It is trapped in there so can't come adrift.
Dave in MN
Well-known member
You should try to get the end play between .003" and .005". I usually set my engines at .003".
As Synchro909 has suggested, you will need to shim or build up behind the front thrust or the rear thrusts. In extreme cases you may need to build up behind the front and rear to keep the crank centered. I have never run into an extreme case so I have only built up the front thrust.
This past weekend, I had a crankshaft that had excessive distance between the front and rear thrust surfaces and I had to deal with the same issue. Not wanting to change the crankshaft, I modified the "thrust washers" instead.
I carefully fluxed the back edge only of the front bronze thrust and then melted solder to the surface. The cohesive properties of the solder built a nice layer right out to the edge of the thrust but kept the solder from spilling over the edges of the thrust. I then used a bench belt sander to flatten the solder surface and monitored the overall thickness of the built up thrust with a 0"-1" micrometer as I carefully removed material from the solder side. You need to check the thrust thickness in multiple places as you are removing material (it needs to measure the same) as the thrust surface needs to meet the crankshaft thrust surface fully.
I was able to achieve my desired .003" end play. I had to add about .018" to the thrust so my case is very close to yours.
I did choose a solder with about a 460 degree melting point so I would consider this a low to mid-range solder as to hardness.
Good Day!
www.durableperformance.net
As Synchro909 has suggested, you will need to shim or build up behind the front thrust or the rear thrusts. In extreme cases you may need to build up behind the front and rear to keep the crank centered. I have never run into an extreme case so I have only built up the front thrust.
This past weekend, I had a crankshaft that had excessive distance between the front and rear thrust surfaces and I had to deal with the same issue. Not wanting to change the crankshaft, I modified the "thrust washers" instead.
I carefully fluxed the back edge only of the front bronze thrust and then melted solder to the surface. The cohesive properties of the solder built a nice layer right out to the edge of the thrust but kept the solder from spilling over the edges of the thrust. I then used a bench belt sander to flatten the solder surface and monitored the overall thickness of the built up thrust with a 0"-1" micrometer as I carefully removed material from the solder side. You need to check the thrust thickness in multiple places as you are removing material (it needs to measure the same) as the thrust surface needs to meet the crankshaft thrust surface fully.
I was able to achieve my desired .003" end play. I had to add about .018" to the thrust so my case is very close to yours.
I did choose a solder with about a 460 degree melting point so I would consider this a low to mid-range solder as to hardness.
Good Day!
www.durableperformance.net
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Dave in MN
Well-known member
Well both in some cases...of my description.
The thrusts you would build up or shim would be the bronze thrusts mated against the block.
You could take your crankshaft to a crank grinder and have them build up the thrust faces of the crankshaft and then grind and polish them. This would eliminate excessive end play. You could likely ask them to add a specific amount. This would be very costly compared to building up the thrusts used in an insert bearing engine.
Are you able to post some photos of the components you are working with. My suggestion of what to do is predicated on using the thrusts shown below or something similar.
Is this similar to what you are using?
Good Day!
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Synchro909
Well-known member
From the original post: I've adopted a fully inserted "rebuilt" motor.
Synchro909
Well-known member
There should be 3 of those crescents that Dave has shown above, 2 at the rear end of the rear main - one in the block, one in the cap. These handle the forward thrust when you put your foot on the clutch. That's why there are 2 of them. There should also be one on the front of the middle main in the block. There is not much pressure in that direction so only 1 is enough.That said, I've not seen thrust washers like that. Maybe others will chime in.
Dave in MN
Well-known member
The photos tell the story! The combination thrust and rear oil seal you show that fits into the rear flange of the block can not easily be modified to change the clearances. I use this product along with the half circle thrust washer shown in Post# 5 above to form a full circle rear thrust.
To adjust your thrust clearances, you will need to focus on the thin thrust washer on the center cap. The path I would take is to carefully remove the thrust attached to the center cap and build up the back side of the thrust with solder. I would then re-install it to the cap and I assume it will require longer pins.
FWIW: I have never had any success running a single rear thrust as your engine is set up. I always install a full circle rear thrust. This process requires machining of the rear cap to allow the installation of the thrust washer I show in post #5. Others have had success with just the bronze combination thrust and seal you show in your photo. The issue I have had when leaving it out is that it will leak oil from the rear main. You have a Burtz rear main seal so a full circle thrust may not be needed to control the oil at the rear main. This seal requires that the built-up seal surface be concentric with the rear main journal.
Good Day!
To adjust your thrust clearances, you will need to focus on the thin thrust washer on the center cap. The path I would take is to carefully remove the thrust attached to the center cap and build up the back side of the thrust with solder. I would then re-install it to the cap and I assume it will require longer pins.
FWIW: I have never had any success running a single rear thrust as your engine is set up. I always install a full circle rear thrust. This process requires machining of the rear cap to allow the installation of the thrust washer I show in post #5. Others have had success with just the bronze combination thrust and seal you show in your photo. The issue I have had when leaving it out is that it will leak oil from the rear main. You have a Burtz rear main seal so a full circle thrust may not be needed to control the oil at the rear main. This seal requires that the built-up seal surface be concentric with the rear main journal.
Good Day!
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Dave in MN
Well-known member
Eliminate the excessive end play and try the engine before you do anything else.
Build up the back side of the thrust on the center cap and re-install it.
When I was describing not having success without a full circle rear thrust, I was referring to a standard rear main oil control system. With the Burtz rear main seal you may not have a leak at the rear main.
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Dave in MN
Well-known member
The picture you show of the rear crank flange has the Burtz seal on it. It fits into the block and the cap. Clean the block and rear main cap groove the rubber seal fits into with a solvent, dry and use some sealant around the perimeter of the seal area that fits into the groove.
You are welcome. Hope everything goes well for you.
Good Day!