Hi All - been awhile since Ive been on here, finally getting back to my coupe project. Started resurrecting an A12 to replace my A15 which keeps eating cams (giving up on solving it....for now at least) A12 was a built race motor which I wor4ked over about 2 years ago, figured out all the valve clearance issues, chamber volumes, has aria forged pistons, worked head and a highly polished crank.

I pulled the pilot bushing out of the crank, measured the ID of the crank bore & its .653, the OD on the bushing I took out is .652, I'd bought a Velao clutch kit awhile back & the bushing that came with it is a National PB-21, it measures .670 OD so Im not cramming a .017 over bush into the crank - what gives??

are there different cranks with different bores? all the bushings I find available are for the .670 OD, I'm going to go measure another A12 bore & see what it says.

I thought all A series cranks were identical save for the stroke, could it be a really early one or possibly from an A10?

any thoughts how to resolve it, havent found a bushing thats .652 available yet...

thanks!

I would try buying a different brand and part number.

I know I've mixed and match before without issue.

> are there different cranks with different bores?

sounds like someone built a race motor and machined it for a different bushing whatever they had on hand. Can you re-use the one that's in there?


All A12 use this Pilot Bushing



Nissan 32202-18000 $3.98
* Fits all A-series A10/A12/A13/A14/A15/A12A
* including E10 Cherry/100A/120A Front Wheel Drive applications

Dimensions:
* O.D.: 0.671" (17.0 mm)
* Width: 0.723" (18.36 mm)
* Bore: 0.48" (12.2 mm)

I thought they were all the same too!

I’ll probably order a few and measure them, seems weird anyone would of machined a crankshaft “down” in size instead of increasing the bore size....

I could reuse the one I pulled but it’s a bit sloppy on the input shaft

Problem solved, took bushing to Machine shop and they turned it down to match the one I pulled !

Still not sure why the smaller bore on the crank, shop suggested crank possibly from an auto trans engine, that make sense?

Automatic A12s are fully machined for a pilot bushing ... i think? everyone that converts to a manual just slaps a standard Pilot Bushing in the end of the crank

funny thing is a 0.653 OD bushing is not common. The L-series Datsuns use an even larger 0.814" OD bushing (PB22). mysterious any chance there is a thin sleeve in the end of the crank?