Spec’s. needed on series 80-81 connecting rods

[Author nameAuthor names are only available to PAS members.]

I am playing with a project and am interested in the specifications on the series 80 and 81 connecting rods. I would like to know the ID of wrist pin, ID of big end, width of the wrist pin and width of the big end, then last would be the center to center measurement. I hope someone has one of these rods laying on the shelve that can be measured. Thanks, Alan

[Author nameAuthor names are only available to PAS members.]

Right off the top of my memory, the Series 80 standard rod journal is 2.00″, the wrist pin is .875″, The width of the big end bearing is 1.50″, but I need to double check that.

The wrist pin is roughly 3.00″ The bore is 3.50″, so I’m subtracting 1/4″ or so from the bore diameter leaves 2.75″-3.00″.

I can check the width of the wrist pin bushing tomorrow.

Series 81 rods are made of Aluminum, the big end is 2.125″ and the wrist pin is .935″ I think,

I’ll check some series 80 and 81 rods in the morning.

Greg L

[Author nameAuthor names are only available to PAS members.]

Hello Alan, sorry for the delay getting these dimensions.

Series 80:

Steel connecting rod material.

std big end journal 2.00″

std wrist pin size .875″

Width of both big end and wrist pin bushing: 1.5″

Center to center 10.5″ [5″ stroke]

Series 81

Aluminum connecting rod material.

std big end journal 2.125″

std wrist pin diameter: 1.0″

width of both rod bearing and wrist pin 1.5″

center to center 10.5″ [5″ stroke’]

Note: the first series 80 rods had only splash oiling for the wrist pin and bushing.

This must have proved to be inadequate. There was a ‘recall’ or modification offered

that had a hole drilled into the rod bearing and the wrist pin bushing on the same side

of the rod’s shaft. A brass or copper tube was fit into the holes, connecting the pressure

lubed rod to the wrist pin., The center of the added brass or copper tube was secured to

the shaft of the rod with two cotter pins around the tube, holes are drilled into the web

of the shaft of the rod. The ends of the cotter pins were spread and then soldered to the

shaft of the rod, as well as the cotter pins to the tube, and sometimes into the holes in

each end of the tube.

So, depending on what your project might be, some connecting rods are without any oil

passageway between the rod bearing and the wrist pin. Some have added-on oil tubes.

The latest rods, starting I think in mid to late 1925 models, have integral oil passageways

drilled through the shaft of the rod, the rod forging was redesigned for this drilled passageway.

Hope this helps with your project.

Greg Long

[Author nameAuthor names are only available to PAS members.]

I Series 80 I once owned had drilled rods. engine #808644 built fall 1925

[Author]

Posts