thrust clearance

oldspert

oldspert

Senior Member
I cannot find the thrust clearance in my red book. I was measuring the flywheel runout and found if I turn the engine clockwise (from the rear) I get a different reading from turning it CCW. So I assume this difference would be the thrust clearance without taking the engine apart and measuring it. I get zero runout on the flywheel both directions just the difference when the crank is rotated a different direction. I get .018 difference between the two.
 

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Turning the engine in different directions will impart forces on the crank shaft in opposite directions due to he helical teeth on the cam drive gears and the oil pump/distributor drive. Probably, the cranks is moving back and forth on you. Tr doing it with the engine in a vertical orientation 9front down) so that the crank is always all the way forward.
 
Most likely the thrust clearance but it could be the orientation of the dial indicator and how it reacts to different directions in the flywheel movement. Try leveraging the crankshaft back and forth with a lever of some kind. You may be able to just push and pull the flywheel.

I don't know what the clearance should be but 0.018 sounds excessive. It is about 0.001 on my Burtz engine.

You could pry the flywheel backwards by levering against the flywheel housing through the hole for the starter motor. And lever it forward by levering the front pulley against something on the engine.
 
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W/the dial indicator mounted as shown in the LH picture, you should be able to easily measure the thrust clearance by simply moving the crankshaft back and forth.
 
katy said:
W/the dial indicator mounted as shown in the LH picture, you should be able to easily measure the thrust clearance by simply moving the crankshaft back and forth.
Click to expand...

That is what I have done, getting the .018 reading. Is that the actual thrust clearance?
Ed
 
Yes, that is the clearance. I don't know what it should be for a Babbitt engine. Richard Knight in Post #3 indicated 0.004 to 0.006 but I suspect a lot of cars have the larger clearance you are getting.

How many miles on the engine since the last rebuild? Are there any other issues such as knocks or a noise when you have the clutch disengaged (clutch pedal to the floor)? Are you concerned about the trust clearance? I don't know what to do to reduce it.

When you are at a stop sign or stop light put the car in neutral and take your foot off the clutch to minimize wear on the thrust bearing.
 
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nkaminar said:
Yes, that is the clearance.
How many miles on the engine since the last rebuild? Are there any other issues such as knocks or a noise when you have the clutch disengaged (clutch pedal to the floor)?
Click to expand...

Have no idea how many miles are on the rebuild. Has .030 overbore, so probably only one rebuild. The reason the engine is out is for a new clutch, I had to push the clutch pedal all of the way down to the floor to disengage the clutch so I am checking everything I can before it goes back in.
Ed
 
The .004-.006 Is what I used when re babbitting and align boring engines. Preferably .004. your .018 is not the end of the world. If the thrust Babbitt is not broken or falling out just use it. Will have no real affect on the clutch.
 
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