pilot bushing clearence

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pilot bushing clearence

Postby gramps » Tue Jan 24, 2017 10:22 am

SBC after driving in bushing ID measures .589" I believe T-10 input shaft measures .590", what should the clearance be between the input shaft and the ID of the pilot bushing?

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Re: pilot bushing clearence

Postby BigBlocksOnTop2 » Tue Jan 24, 2017 12:08 pm

Install a roller bushing. If going bronze I say .0025-.004 clearance.

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Re: pilot bushing clearence

Postby bracketchev1221 » Wed Jan 25, 2017 7:43 am

This is an issue. I did a job years ago where I pressed the bushing in and the trans would not pull into the bushing. It did exactly what you describe. The OD of the bushing was too large and it pinched down the opening. Now if possible, I try to slide the trans in the bushing before installing the clutch. I am not sure what the actual clearance should be per spec. But you do want the bushing to just make it over the input shaft.

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Re: pilot bushing clearence

Postby autogear » Wed Jan 25, 2017 9:16 am

First off; check your pilot bushing with a magnet. It should be NON magnetic. Significant iron inclusions in the sintered bronze can and will damage the input pilot. If it IS magnetic, replace it with one that isn't.

We would like to see the ID of the bushing at .5925 - .5920

We prefer Oilite bronze bushings such as p/n 0-127-006. These are self oiling and non magnetic; but, any non-magnetic pilot bushing is fine. Roller bearings are the $14 answer to the $9 problem. We've seen some fall apart prematurely, the hardened needles can damage the pilot of the input if the bearing is installed incorrectly, or there is excessive runout in the bellhousing as installed. They don't tolerate misalignment at all, a bushing can tolerate a little bit. That leads to the next issue.

Check your bellhousing for concentricity with the pilot bore and parallelism. We like to see the bellhousing aligned to within .010 TIR.
Follow the video here: https://www.youtube.com/watch?v=rzc2tmFKUhI

I also recommend the RobbMc alignment dowels he mentions in the video.

Auto Gear does not receive any compensation for recommending the video or the RobbMc parts therein.

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Re: pilot bushing clearence

Postby MadBill » Wed Jan 25, 2017 6:42 pm

I never understood the appeal of roller pilot bearings on the track, given their intolerance for misalignment and tolerances, greater susceptibility to clutch wear particles and considering most race cars don't spend a lot of time running with the clutch disengaged.. (although I did see a Trans Am SB2.2 engine with over 0.200" wear on the thrust surface of the crank after 30+ laps under yellow at Mosport behind a pace car that would have been left in the dust by your average parade float.. #-o )
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