I would like to find four pistons for Cat thirty larger than +.040 . I have a set of jugs with no welds that are +.040 with considerable wear/corrosion and would rather bore to +.060 or greater than sleeve them.
Also open to a set of 35 pistons
Thanks

Do not rule out gas Thirty Five pistons. I had a PS Thirty come in with a set of them in it. Only .125" overbore.
Thanks
Ken

"naylorbros" wrote:

Do not rule out gas Thirty Five pistons. I had a PS Thirty come in with a set of them in it. Only .125" overbore.
Thanks
Ken

You said only .125! I have a set of 35 pistons, but they are for my 35. I will have to hold a caliper up the the jug and see what +.125 would look like. Surprised there were not any after market over bore kits like the Volkswagon had.

I will not get home until late tonight or I would post a picture tomorrow of a Thirty jug that has been bored for a Thirty-five piston along with the piston. It must have been one hot Thirty because the piston are either 6000' or 12,000' high Altitude pistons. I will get over to the shop tomorrow and take some pictures.

"naylorbros" wrote:

I will not get home until late tonight or I would post a picture tomorrow of a Thirty jug that has been bored for a Thirty-five piston along with the piston. It must have been one hot Thirty because the piston are either 6000' or 12,000' high Altitude pistons. I will get over to the shop tomorrow and take some pictures.

Here is the 35 next to the 30
The compression height is .070 less
Pins the same
Rings 3/16 vs 1/4

I grabbed a few pistons and a jug for pictures last night. In the piston picture the left piston is a 1B4190. It is a 12,000 ft high altitude piston is standard size for a Thirty Five. The middle piston is a 1A2908. It is a 6000 ft high altitude piston in .040" oversize for a S/PS Thirty. The right piston is an aftermarket standard piston for a Thirty. The second picture shows a Thirty jug that has been bored to fit the Thirty-Five piston.

Check ring availability and cost before you decide to bore out the cyl. 30 years ago I thought I was so lucky, (smart) when I came across a set of 30 .080 pistons which were just right for a new over bore cylinder, only to find out that I had to have Niagara piston ring make a new set of rings at a high price. Also check with hydraulic machine shops as they have sources for old style wide piston rings used in hydraulic cylinders.

"naylorbros" wrote:

I grabbed a few pistons and a jug for pictures last night. In the piston picture the left piston is a 1B4190. It is a 12,000 ft high altitude piston is standard size for a Thirty Five. The middle piston is a 1A2908. It is a 6000 ft high altitude piston in .040" oversize for a S/PS Thirty. The right piston is an aftermarket standard piston for a Thirty. The second picture shows a Thirty jug that has been bored to fit the Thirty-Five piston.

Hello naylorbros, I just noticed the piston on the right has it's oil ring above the piston pin, and the 4th compression ring below the pin, I wonder why that is?

Hello Russell Turner, I'm going through that exercise right now, about to order new rings from Niagara for my standard size Cat 30 pistons with worn ring lands, I haven't got a quote yet but hopefully it's not like the $680 I got quoted here in Australia a week ago to get the new rings made!
Mike

No idea on why the rings are in the wrong order. I never noticed it before and I usually see things like that. That is the way they came out of the tractor when I took it apart or when I bought that set of pistons. I can not remember which it was.

i was told by a old timer that there was a cummins piston that would work in a thirty. i do know that you can make a really nice sixty with JD D pistons lol.
don't know any more than that.