[mikies'63]

Hi and thanks to all for your help and advice with my '63 Nova for the past several years!
I'm having a problem installing a Muncie M20 in my '63. It has the original 194 L6.I have had a Powerglide and a 700R4 and am now putting in the Muncie M20. At the suggestion of my friend who is helping me with this project, I got a pilot bushing NAPA part# 27MP0028. He likes these non-magnetic sintered bronze pilot bushings as they are like the original ones in GM manual transmissions.The OD of the pilot bushing that came with my clutch kit and the one from NAPA are identical, but they are both too large to fit in the end of my crankshaft by about 40 - 50 thousandths. We could turn either one of them down on a lathe to correct the size but we are wondering if there isn't a cleaner, simpler solution. Also if we end up putting them in a lathe to make them fit the crank what is a commonly accepted interference fit between the bushing and the crankshaft.
We are wondering if this has anything to do with the fact that this 6 cyl has always been connected to an automatic trans from the time it cane off the assembly line until now.
Thanks for any help
Mike

 

[Redrider66SS]

from what you say it almost sounds as though there is a difference from the auto crank an manual crank. well that bushing is not a real tight fit, as i watched a guy use a bread ball in the bushing with a drift punch to push an remove the bushing.

 

[AllyMcReal]

No difference in the cranks, if stock. Might have been a strange run of an aftermarket crank maker, but no difference. What are we, Mopar guys??! Cranks the same.

I have had just this problem before, and it's not the crank, it's the bushing. Way too much interference. I'd think .003-.005 interference max. The input shaft surface that rides on the bushing, especially if it's one of those bronze ones that's impregnated with oil, won't have a problem spinning in the crank if that's what you're worried about; way too much surface area where the bushing OD meets the ID of the crank hole.

I bet you find a significant variance from bushing to bushing in the aftermarket supplier market.

 

[Twinshadows]

I agree with Frank ^ ^ ^ ^ ^ ^ ^ ^ on this . . . . my car was a factory powerglide car
. . . then, installed a w/c T 5 trans . . . . . . and, used / installed
the "pilot bushing " that came with my (Summit) "clutch kit " .
The "six - cylinder cranks are the same - - automatic & standard - shift crankshafts .
My pilot bushing WAS A Tight Fit , but I did use it . (installed since - - March , 2018 ) .

just FYI . . . . .. jim

 

[Redrider66SS]

so quality control went out the door.

 

[mikies'63]

A buddy of mine turned up some information on the internet that seems to shed some light on this issue. Following is a link to specs on some pilot bushings used in various GM and Ford vehicles.
AGF pilot bushing specs (click for sheet of specs)
Looks like the Chev's engines with Powerglides may have been assembled with a crank machined for smaller pilot bushings. This would clear up this mystery!
Anyone have any comments on this?
Mike

 

[Twinshadows]

Thanks Mike . . . . interesting chart . . . . I DID save that too my "Nova Info" folder .

Plus . . . . Mike - you do know ; that if you ever go back = and, want to use your "Automatic
Transmission again - - - - - that you DO NEED to REMOVE , any pilot bushing . . ( Do Not use a
"Pilot Bushing with an Automatic transmission" ( the torque converter will not "seat - in" the crank .

just FYI . . . . jim