Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Wrist pins a tight fit

Wrist pins a tight fit

Post Thu May 17, 2012 8:56 am

Posts: 7
Any thoughts on how tight is tolerable for the wrist pins? I've got one that is a little too tight for the piston to "fall over" from its own weight, and the other is tighter, I can move it by hand, but there is definitely some resistance, about like opening a two liter bottle of carbonated beverage. If this is too tight, can I hone the connecting rod bushing with a socket wrapped in emory cloth, or some other method to avoid a trip to a machine shop? All the parts are new, probably repro.


Mark Robinson

Post Thu May 17, 2012 5:40 pm
Pa Site Admin

Posts: 5843
Location: Ohio USA

Run the correct size reamer through them.

Post Thu May 17, 2012 8:15 pm

Posts: 391
The pins need to be a slip fit in the small end bushings and a light press in the pistons. If the pistons are warm the pins should press in by thump pressure. The pins should slide through the small end bushes with no slop and very minimal drag. If dropped in on end they should slide through by gravity!

Post Sun May 20, 2012 5:46 am

Posts: 36
I have used a brake cylinder hone to ease that last half a thousandth out of those bushes.
Run it slow and real careful and check for size very often, it only takes a few turns to knock off the high spots and free up the fit. Use WD40 as cutting lube.

Return to 45 Flatties