MC91B1 rod, piston, wrist pin assembly

[Ryan Courts]

It's funny to what lengths we go today to put the pin into the rod carefully. I remember in '59, Pop took an oak block and cut a hole through it and a concave surface for the piston to sit in. He took an old 1/4" drive socket extension and turned it down to fit nicely inside the wrist pin. He simply shoved the pin in and out with the vise and those crude tools. I was still using that same tool in '78 to install the pin in my open 101 engines, after I modified the radius of the concave surface to fit the bigger piston. It always worked, and I never had a pin failure on my B Limited Macs. I wouldn't think of doing that job today without the "proper" tools. Of course, I don't use a press, simply a GEM piston tool. We "made do" back in the early days. I would not be surprised that if you were to dig through Charlie Craibe's old boxes of stuff that came from Pop, you might find that oak block tucked away in among the old Mac parts. Ted

I'm going to have to "Make Do" for sure. I'll get it. Thanks for the responses.

[Bob Alexander]

I just tore down an engine to freshen it up for Avon and discovered, to my dismay, that the rod cap was cracked. Why it didn't fly apart the last time it was run is a mystery, just lucky I guess. So I have to change the rod. Problem is it's something I've never done, I always had the machine shop change the piston when I had a block bored.

I know it's a press fit between the rod and pin, but what's the procedure? The pin bearings are open on one end and closed on the other. Do you push from the open side and drive the closed bearing out with the pin? What is the proper way to support the piston?

Help!  BP

Bill:

I sent you a pm.

Bob Alexander

[Terry Bentley]

Some tools that were available when Macs ran the roost.

[steve welte]

my puller is a 1/4" nut tapped to 5/16" thread inside. It travels through the bearing and rod eye when pulling. Knock the edges off the nut and check for fit. A long 5/16" TAP bolt with a nut through a thick alum block so you can counter sink a hole for the wrist pin to travel into. I do not press the pin back in. have a 1/2" bolt turned down so part of it fits into the pin for guiding. Tap into place after freezing the pin and warming the rod with a heat gun. Hardwood block with a curved area to fit the piston for support. Lube the bearings and the pin when tapping into place.