Well, I'm back(ish). I did some searching and didn't come up with anything from this, so I apologize for poor googlefu ahead of time if it's been covered. Has anyone done any custom piston work with the Kubota V2203, such as turning down the diameter of the crowns?

It's been a long time, so for people who aren't familiar with what I'm talking about, here's a short recap:

I built several iterations of this Jeep conversion over the course of several years having a lot of trouble with piston scrub and seizing up. One engine lasted 3 years, but it was the highest hours when I got it. Even before this one eventually failed, it would have strange behavior on long pulls, like mountain passes where it would pull strong about halfway up the pass, then slowly get weaker and weaker with EGTs rising without a change in load. I eventually gave up and sold it to Rangmar, who put a brand new engine in it that proceeded to seize the same way. He did an extremely thorough teardown, measuring parts and comparing to other engines (cummins), etc, and determined that the Kubota engines don't taper from the crown to the skirt to allow thermal expansion of the crown as you would expect from an automotive engine. It's been a couple years, but our theory at the time was that I was using nearly new engines, and everyone else we knew about started with quite high hours by comparison. We're talking thousandths of an inch difference, so it could be a matter of the long 'break in' allowing them the clearance necessary. I ended up buying the Jeep back last year, and am starting to get the bug to do something with it again, probably late winter or early spring.

I still haven't heard of anyone else who has had the same issue yet, but the solution would seem to be to either order custom pistons ($$$), or see if these can be turned down above skirt.

Sorry for any lack of or slow responses over the past few years, engaging in forums and media was taking too much time in my life, so I'm probably not going to be super responsive, and just check back occasionally.

Thanks,
James

 

I'm following this thread because I just completed a V2203 swap and in the process of tuning it to make more power and tuning the transmission shift points to make it drivable. I didn't know this was a problem with the Kubota engines and the first that i've heard of it. The engine in my swap had low hours before the swap 7200. This is my 1st swap and Im still learning quite a bit about diesels. What EGT were you seeing regularly before seizing? My current setup, I see 1100* F while climbing a hill in 3rd gear and the torque converter locked. The pyrometer is in the adapter pipe between the manifold to the K03 turbo. What was your injection timing, and what if any effect would that have on the pistons seizing? From what I read retarded timing (closer to TDC) will have lower rpm power and more heat in the exhaust manifold at higher rpm. Advanced timing will have higher heat in the cylinder and higher rpm power. My current setup with no shims under the IP is 8.5 * btdc, it seems to struggle at higher rpms and have been thinking of advancing the timing more. I hate the idea of pulling the engine out to rebuild it with different pistons, but I built this to be reliable.
Thanks, Ralph