Clutch Pilot Bushing -Runout Tolerance???
Thread Starter
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Clutch Pilot Bushing -Runout Tolerance???
I cant seem to find this spec. anywhere.Can anyone help me out? i'm also looking for the runout spec for the crankshaft flywheel flange--(the surface the flywheel bolts to)I have a 69 with the pilot bushing out by .003 and a gulded trans. input shaft which caused a vibration when the clutch was down to the floor.----I also have a 71 with the flywheel flange face out .0045 which puts the flywheel out by .023 at the outer edge of clutch surface which creates a major foot massage.Flywheel is dead nuts.When I confronted the engine builder about the flange surface he said there is no known spec for this-but you would think since he straightened the crank and then turned it .040 under he should be aware of some specs.On this tolerance I would like proof if possible to take to him otherwise he said he couldnt do anything about it. Thanks Roger
Thread Starter
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by Z-man
Wow - that is a lot for just the flange. Not that I know what I'm talking about, but can you shim it? I don't know about runout specs...
Team Owner
Joined: Apr 1999
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
The whole idea of straightened or ground cranks really bothers me. We are not back in the 50's and 60's working on some farm truck!
You can buy the cheaper forged cranks for less than the labor you probably spent.
The crank flange should have "ZERO" runout. When you bolt on the flywheel it should have "ZERO" run out. The pilot bushing should be true and on dead center. Your only adjustment should be setting the bell housing runout with the block dowls. This centers the tranny input shaft to the pilot bushing.
Here is a clip from a service manual - they give a max runout of .0016. That is less than 2 thousants of an inch. Then its new crank time. It will cause clutch chatter and vibration.
-- mm -- in
Crankshaft
Main Journal Diameter 67.239-67.257 mm 2.6473-2.6483 in
Main Journal Taper 0.005 mm 0.0002 in
Out Of Round - Max 0.005 mm 0.0002 in
Flange Runout-Max 0.04 mm 0.0016 in
Cylinder Block Main Bearing Bore Diameter 72.155-72.168 mm 2.8407-2.8412 in
Crankshaft Main Bearing Inside Diameter 67.289-67.316 mm 2.6492-2.6502 in
Main Bearing Clearance 0.019-0.064 mm 0.0008-0.0025 in
Main Thrust Bearing Clearance 0.032-0.077 mm 0.0012-0.0030 in
Crankshaft End Play 0.060-0.210 mm 0.0024-0.0083 in
Crankshaft Flange Runout-Max 0.04 mm 0.0016 in
You can buy the cheaper forged cranks for less than the labor you probably spent.
The crank flange should have "ZERO" runout. When you bolt on the flywheel it should have "ZERO" run out. The pilot bushing should be true and on dead center. Your only adjustment should be setting the bell housing runout with the block dowls. This centers the tranny input shaft to the pilot bushing.
Here is a clip from a service manual - they give a max runout of .0016. That is less than 2 thousants of an inch. Then its new crank time. It will cause clutch chatter and vibration.
-- mm -- in
Crankshaft
Main Journal Diameter 67.239-67.257 mm 2.6473-2.6483 in
Main Journal Taper 0.005 mm 0.0002 in
Out Of Round - Max 0.005 mm 0.0002 in
Flange Runout-Max 0.04 mm 0.0016 in
Cylinder Block Main Bearing Bore Diameter 72.155-72.168 mm 2.8407-2.8412 in
Crankshaft Main Bearing Inside Diameter 67.289-67.316 mm 2.6492-2.6502 in
Main Bearing Clearance 0.019-0.064 mm 0.0008-0.0025 in
Main Thrust Bearing Clearance 0.032-0.077 mm 0.0012-0.0030 in
Crankshaft End Play 0.060-0.210 mm 0.0024-0.0083 in
Crankshaft Flange Runout-Max 0.04 mm 0.0016 in
Thread Starter
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by gkull
The whole idea of straightened or ground cranks really bothers me. We are not back in the 50's and 60's working on some farm truck!
You can buy the cheaper forged cranks for less than the labor you probably spent.
The crank flange should have "ZERO" runout. When you bolt on the flywheel it should have "ZERO" run out. The pilot bushing should be true and on dead center. Your only adjustment should be setting the bell housing runout with the block dowls. This centers the tranny input shaft to the pilot bushing.
Here is a clip from a service manual - they give a max runout of .0016. That is less than 2 thousants of an inch. Then its new crank time. It will cause clutch chatter and vibration.
-- mm -- in
Crankshaft
Main Journal Diameter 67.239-67.257 mm 2.6473-2.6483 in
Main Journal Taper 0.005 mm 0.0002 in
Out Of Round - Max 0.005 mm 0.0002 in
Flange Runout-Max 0.04 mm 0.0016 in
Cylinder Block Main Bearing Bore Diameter 72.155-72.168 mm 2.8407-2.8412 in
Crankshaft Main Bearing Inside Diameter 67.289-67.316 mm 2.6492-2.6502 in
Main Bearing Clearance 0.019-0.064 mm 0.0008-0.0025 in
Main Thrust Bearing Clearance 0.032-0.077 mm 0.0012-0.0030 in
Crankshaft End Play 0.060-0.210 mm 0.0024-0.0083 in
Crankshaft Flange Runout-Max 0.04 mm 0.0016 in
You can buy the cheaper forged cranks for less than the labor you probably spent.
The crank flange should have "ZERO" runout. When you bolt on the flywheel it should have "ZERO" run out. The pilot bushing should be true and on dead center. Your only adjustment should be setting the bell housing runout with the block dowls. This centers the tranny input shaft to the pilot bushing.
Here is a clip from a service manual - they give a max runout of .0016. That is less than 2 thousants of an inch. Then its new crank time. It will cause clutch chatter and vibration.
-- mm -- in
Crankshaft
Main Journal Diameter 67.239-67.257 mm 2.6473-2.6483 in
Main Journal Taper 0.005 mm 0.0002 in
Out Of Round - Max 0.005 mm 0.0002 in
Flange Runout-Max 0.04 mm 0.0016 in
Cylinder Block Main Bearing Bore Diameter 72.155-72.168 mm 2.8407-2.8412 in
Crankshaft Main Bearing Inside Diameter 67.289-67.316 mm 2.6492-2.6502 in
Main Bearing Clearance 0.019-0.064 mm 0.0008-0.0025 in
Main Thrust Bearing Clearance 0.032-0.077 mm 0.0012-0.0030 in
Crankshaft End Play 0.060-0.210 mm 0.0024-0.0083 in
Crankshaft Flange Runout-Max 0.04 mm 0.0016 in
Thread Starter
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Originally Posted by gkull
Just for future reference. automatic equiped SBC's don't even use a pilot bearing.
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