diesel 35 pony motor bore size

Can't quite pin it down to the 35 model but the specs I have show the vertical pony motors in just two bore sizes....either 3-3/8 in. or 3-5/8 in.
I suspect yours is the smaller version.

I've been through every piece of Cat literature where the Diesel 35 pony specs might be hidden, and haven't found a thing.
All I've found .. is that the 1933 brochure on the Caterpillar Diesel, featuring the development and design of the Cat diesel, and which shows all the intricate features of the Diesel 35, 50 and 75 .. shows a picture of the 4 & 6 cyl pony engine, and outlines the all features of the "gasoline starting engine" .. but give no specs.

The text with the pic states that .. "this engine is the starting engine for the 4 & 6 cylinder engines. The starter for the 3 cyl engine is also a 2 cylinder gasoline engine, but of slightly different design".

This jells with OM's info, that it appears the Diesel 35's, D6100 engine pony, is the smaller 3 3/8" bore .. while the D7700 and D11000 used the 3 5/8" bore pony.

By 1935, the starting engine for the revised 5 3/4" bore, D13000, D8800 and the D6600 engines, was standardised .. with all three engines using the same 3 5/8" bore x 4" stroke, 17.5HP @ 2100 RPM, pony engine.

The Diesel 35 & 40 Starting engines cylinder bore size is 3 3/8 ( Same as the Cat 10 .Same pistion, rings, valves, side valve cover). The Diesel 50 & 75,RD6, 2H D6, RD7 9G D7,7m 3T 4T, RD8 1HD8 and the 2U D8 used the larger 3 5/8 bore, they needed the extra power, more cylinder,s. The engine block,s themselves are interchangeable on all the RD's,2HD6 & the 9G D7, so it is possible to have the larger bore engine on a D35 & D 40.

Ken P. is right on you need to know the casting/part number of the block to know or disassemble the motor to know as the older blocks look the same from the outside but can be different bores. ran into that when we restored my diesel 40.

thanks for your help, It looks like 3 3/8 size, now can anyone tell us what the piston skirt clearance is ?

O.K. - Here's the rub .. are you on standard bore? .. or .020", 040" or 060" O/S? .. and are you using iron, or aluminium pistons?

The skirt clearance is different for every bore size, and for iron or aluminium pistons.

I know it's quite likely that you are no longer on original bore or original iron pistons .. but whether you are, or not .. the bore size and piston construction is still needed to get the right clearance specs .. 😎

Hi Oz, thanks for your reply we have std aluminium pistons ,cheers

This should cover it:

O.K. - OM beat me on the scan while I was snoozing .. that's the same info as I have. That should see you right.