pilot bushing - Chevelle Tech
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post #1 of 29 (permalink) Old Jun 21st, 19, 8:08 PM Thread Starter
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butch
 
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pilot bushing

hey all , iv been reading about the pure bronze pilot bushing and the brass with steel bushing, witch bushing do u suggest
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post #2 of 29 (permalink) Old Jun 21st, 19, 8:21 PM
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Re: pilot bushing

Nothing magnetic.
Oilite
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post #3 of 29 (permalink) Old Jun 21st, 19, 9:32 PM
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Re: pilot bushing

National Bearings PB-646-HD is a good one available at many auto parts or 5speeds.com sells some good bushings.
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post #4 of 29 (permalink) Old Jun 21st, 19, 10:59 PM
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Re: pilot bushing

If a magnet sticks to it then do not use it.


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post #5 of 29 (permalink) Old Jun 21st, 19, 11:33 PM
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Re: pilot bushing

Quote:
Originally Posted by blm View Post
National Bearings PB-646-HD is a good one available at many auto parts or 5speeds.com sells some good bushings.
National Bearings PB-656-HD

https://smile.amazon.com/National-PB...gateway&sr=8-1

Are you running a stock bell housing? If you're running anything else you should measure the end of your input shaft to trans face and compare it to the depth of the bell housing trans mount face to the bushing in the flywheel. Your input shaft should be supported by about 5/8 inch into the bushing.(19/32 to be exact) Extended bushings are available to make the correction.
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post #6 of 29 (permalink) Old Jun 22nd, 19, 11:15 AM Thread Starter
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Re: pilot bushing

im running all stock drive train, what im trying to find out why is the pure brass pilot bearing prefered ?
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post #7 of 29 (permalink) Old Jun 22nd, 19, 12:48 PM
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Re: pilot bushing

Actually it's not brass, it's bronze that has been oil impregnated. You may not see the oil in the bearing I posted, but if you heat it up the oil will start to come out from the pores and you can see and feel it. To prevent a dry start up. I will apply engine oil to the input shaft. I use to apply a little high temp grease, but the internet told me that the soap in the grease blocks the pores. So I bought into that even though the grease has worked for many years on my installations. 30 plus since 1981

There's 2 killers when it comes to pilot bearing, one is improper bell housing alignment. The parallel and concentric alignment should be checked and adjusted on ALL installations. The second which also kills throw out bearings is continued application or riding of the clutch. So kicking it into neutral while waiting at long traffic lights will extend the life of these parts.

Oilite is also used in bronze and iron impregnated bearings. For some applications this would be preferred as it will last longer. However, the Muncie input shaft is not hardened and the metal will cause heat and wear on the Muncie shaft. The metal in the bushing overheats and starts to weld itself to the input shaft. Think of bronze with metal particles in it. The metal acts as an abrasive until it overheats and attaches itself to the input shaft.

Roller bearings are not advised for use on the Muncies for street use. The Muncie shaft is non hardened and when the bearing fails, Will damage the input shaft. When a bronze bushing exceeds it's life, you'll develop shifting issue, vibration, or noise, yet it is more forgiving than the steel contained in the failed roller bearing.

Oilite is a trademark of Beemer Precision but was initially invented by Chrysler in the 30's, so many bearing manufacturers will not pay royalties to use the trademark, but still produce a similar product.

https://en.wikipedia.org/wiki/Oilite
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post #8 of 29 (permalink) Old Jun 22nd, 19, 1:01 PM
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Re: pilot bushing

A bronze, or better, oilite bushing will not gall the input shaft, it’s more of a “consumable” item like clutch discs and brake pads. If a magnet sticks to the bushing, it has iron in it. Once the bushing heats up, the iron will try to “transfer” (gall) to the input shaft. If you haven’t seen one do this, it looks like the input shaft outer surface has smeared. This will cause all sorts of problems.
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post #9 of 29 (permalink) Old Jun 22nd, 19, 1:27 PM
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Re: pilot bushing

Butch,
In addition to using an all bronze bushing there is another issue that is important. Measure and double measure the outside diameter of the pilot bushing and the inside diameter of the crank bore. The bushing should be no greater than .002 larger than the crank bore. One could MAYBE get away with .003. After that you will have to adjust the bushing diameter. Either the inside or outside. If you try to force in anything larger it will just compress and the interior dimension and not clear the input shaft. Also if you do force in a bushing larger than you you will have to remove it and that will not be fun.
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post #10 of 29 (permalink) Old Jun 22nd, 19, 2:06 PM
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Re: pilot bushing

Freeze your bushing in a freezer before installation. It will make installation much easier.

Then, let it return to room temp before checking the inside diameter of the bushing to input shaft clearance.
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post #11 of 29 (permalink) Old Jun 22nd, 19, 5:29 PM Thread Starter
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Re: pilot bushing

hey thanks fellas for the info, i got lucky and found an all bronze bushing at napa, part number is b 656 only one they had, do u think this will be ok. i will double measure to make sure it fits and i will freeze it before installing, again thanks for all the good info thats what make this site so awsome .
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post #12 of 29 (permalink) Old Jun 22nd, 19, 8:43 PM Thread Starter
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Re: pilot bushing

al , how long should i leave the bushing in the freezer ?
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post #13 of 29 (permalink) Old Jun 22nd, 19, 9:12 PM
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Re: pilot bushing

Quote:
Originally Posted by p40 View Post
al , how long should i leave the bushing in the freezer ?
I throw mine in the night before. But an hour or two might do the trick. The metal will contract ever so slightly and ease the installation.

Napa b 656 is non magnetic oil impregnated and good to go.

Uninstalled interior dimension is .593. Installed it may close to .592. If any tighter it should be reamed .592

Your input shaft should measure to .590.

You want .002-.003 clearance between the shaft and bearing.
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Last edited by DUTCH MAX HEADWORK; Jun 22nd, 19 at 9:29 PM.
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post #14 of 29 (permalink) Old Jun 23rd, 19, 1:37 AM
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Re: pilot bushing

Don't rely on a plastic alignment tool for bushing clearance. They are smaller diameter than a real input.

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post #15 of 29 (permalink) Old Jun 23rd, 19, 11:00 AM Thread Starter
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Re: pilot bushing

Quote:
Originally Posted by LevonH View Post
Don't rely on a plastic alignment tool for bushing clearance. They are smaller diameter than a real input.
thanks iv got an old input shaft i will use
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