Good morning! I wrote to JP Pistons to inquire about oversized pistons for my D4 7U 36219 pony motor, got a quote and was attempting to place my order and they wrote back: "The piston we have is for the starter engine for D2, D4 & RD4 tractors years 1936 – 1940 not 1956. Would this be suitable?" Are these pistons compatible with my engine? My parts book shows a standard piston being 2F3665. I need .020 oversized. Any suggestions are welcome. Thanks for the help! Elton

I'm not the last word but bore and stroke is the same early and late. Might be some differences is rods, pistons pins and retainers but I'd think the pistons should work,
The 0.020" over version of the 2F3665 is a 8H2762.

that's interesting stuff Mag, never heard of 6 rings...not gasoline for sure...

diesels i think were common with 4 rings..many years and applications...

all engines have made leaps and bounds regarding engineering and reliability...efficiency etc

You were to quick for me. Didn't realize at first I was looking at main engine piston/rods when the topic was pony pistons. My bad and the reason for the quick edit. But for the record 4G D4 main engine pistons are 6- ring

If you want to use standard pistons you can have the pony bores sleeved. I have had several.done by auto machine shop.

I am indeed asking about PONY pistons. From what I have heard the engines are mostly the same except for manifolds etc., but now I need pistons and JP seem to be the only manufacturer of any pistons now. They seem reasonably priced and I need oversized. I guess I gave too much information, the questions should have been are early and later D4 pony pistons the same? Evidently JP Pistons hasn't had the opportunity to check....or maybe they have??? Thanks! Elton

Here's the specs....

i agree with Neil, those are pretty low tech pistons considering whats available today. A few measurements should be all it takes to find something suitable.

-Have you heard of J E pistons? made in California i believe, that's the first thing i thought of, then realized J P, which are Australian made. Both are excellent products. There's quite a few piston manufacturers out there, or there was, this is a difficult time for many business'

JP pistons are good stuff i had to order a piston for a BSA engine it came with rings, gudgeon pin and pin retainers. only took 2 weeks due to manufacture time. it fitted perfect. im sure if you sent them a copy of the spec sheet that OM posted they would be able to confirm it would fit and if not they may be able to make you a pair that will as all pistons are rough cast and then machined to size from a basic blank. or you could go billet aluminium and get a shop to turn up a couple for you.

as long as the crown to pivot centre is the same or slightly less(it would drop the compression slightly), the od is correct and pin size is correct it would work.

i seem to remember jp had the specs for the pistons they make on there website. they would provide them by request of course too.