Hi,this Pony Engine Spec sheet should help you with the tolerances these engines have from new and can safely be re-assembled with--they are not high performance Indianapolis 500 race engines and so are fairly forgiving.Cheers,Eddie B.

Neil wrote:

That's not too bad for an 80 year old design. It'll run fine with that gap. New pistons available from JP Pistons in Oz. I put some in my 5U's pony and they're top notch. There may be some local producers I'm not aware of (I'm in Western NY).

Thanks Neil, I couldn't find JP Pistons(tried Google), but I did find JE pistons in California and I emailed them the 2 3/4" .020 oversize piston specs. Will let you know what they say.

edb wrote:

Hi,
this Pony Engine Spec sheet should help you with the tolerances these engines have from new and can safely be re-assembled with--they are not high performance Indianapolis 500 race engines and so are fairly forgiving.
Cheers,
Eddie B.

Thanks Eddie B. I'm having a really difficult time reading these specs, the image is quite small and fuzzy. Do you have a larger image by chance?

eisenhart wrote:

Neil wrote:

That's not too bad for an 80 year old design. It'll run fine with that gap. New pistons available from JP Pistons in Oz. I put some in my 5U's pony and they're top notch. There may be some local producers I'm not aware of (I'm in Western NY).

Thanks Neil, I couldn't find JP Pistons(tried Google), but I did find JE pistons in California and I emailed them the 2 3/4" .020 oversize piston specs. Will let you know what they say.

-their (JE) automotive pistons are top-shelf, interested in what you find!

Hi,
seems I have two of these Page 4 of the Spec sheet set--one blurry and one clear, naturally I got the wrong one so that is now deleted.
Hope this one is clearer for you.
Cheers,
Eddie B.

jp pistons will make you some the killer will be the freight. find another machine shop that offer re-boring services the bores will need to be bored to a size for the job to last simply putting oversize pistons in doesnt work as bores wear oval due to the rotational forces in the engine end they also only wear part of the bore so new pistons if slightly longer skirts may jam in the bore and then bad things happen. look in your local phone directory. also ask your mechanic who they use. it wouldn't cost much to send a bare block and crank to another town to get it done engine re-builders do this all the time they may even do deals with a courier company to get better rates just ask around.

Hey guys this is Scoop, I’m also in the middle of a Pony Motor rebuild. It’s a D318 out of a D6 8U Dozer with 3-1/8” bore x 3-1/2” stroke pistons. Waiting to see how the tolerances come back from machine shop but my measurements indicate it will likely need to be oversized .02” to .04”. Doing very well with many parts I need from Florin and some from local CAT dealer. Toughest part now is locating O’size piston supplier. Spoke with JE Piston, the guy there said I would have to send them a Piston to reverse engineer it ... ain’t doin that. Also contacted someone from JP Piston, guy there said to send specs to This email address is being protected from spambots. You need JavaScript enabled to view it.. Looks like a stateside JP Piston rep from website. Having a tough go at it, hopefully here back from JP soon. Any other sources out there if anybody listening in and may know of would be greatly appreciated. Also wonder just how much getting those darn things to the house is gunna cost, anyone care to venture a guess?

I have 4 pistoms 2f3669 with ring on and the look lke 3.122
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