Confirmed piston replacement solution for the 340s engine

[lwb140]

pj please understand im satisfied dementionally the pistons are a drop-in . im the guy that ordered 4 of these to look at on a whim and then called back and ordered the remainder of their inventory after looking at them , im just glad that mitch is using the parts for what i sold them to him for , and not chickening out and using them for paperweights just because they dont have the correct deere part number typed on the box, way to go guys wade

[JoeRainville]

Hi Guys,

Glad to see more members are working on solutions to fitting pistons to our beloved, yet slightly evil, 340/s'. PJ, it's great to have another engineer on the problem, but please don't be so deffensive. NO DOUBT I have ticked off a few past/present members over the years with some my idea's, preproductions or mistakes, it happens.

I can appriciate the time and effort you have put into rebuilding Mitch's 340/s motor. I have concerns about the ring hanging up also, but your chamfer may solve the problem and be an acceptable solution. On the Kawi 440 Liquids I am doing I-500 rebuilds, they have a center rib to support the ring on the intake side to avoid snagging a ring, but the smaller exhaust port does not. I assume there is an acceptable amount of ring exposure that works, and there is a tipping point where the ring can catch. It may also mater where how the rod is side loading the piston. For example, there is little side load at TDC but a lot when the piston is moving up from BDC as the crank pin approaches 90 degree from the bore center line.

I am guessing the motor engineers found that they needed that little dip in the middle of the port, and moved the rings ups for several of the reasons you already mentioned.

Over the years, Troy, Linder, and many 340/s collectors have shared their thoughs and solutions on this board. Troy's method was a well thought out solution, and is testing out well so far. I look forward to seeing Mitch run his motor and get some miles one them. As they say, there is more than one way to skin a cat. And I like data.

I have also been working on a few solutions for my restored 340/s. I am sending a set of beat up 340/s jugs to Milenium Technologys this fall. They tell me they can nicasil a worn iron bore that is worn out to 10 to 20 thousands over. The original NOS rings should work. I am also having a used set of pistons ceramic coated to help take up some of the wear. I will then run this set up and let the guys know how it works. If try it and like it, great. If not, that is fine too. If it works well for a few seasons, I will probably try it on a Dator.

Glad to see the passion is alive and well for our Deeres. Would like to see a bit more respect to new and alternate ideas to keeping these old girls out on the snow, where they belong.

-Joseph D. Rainville

[Cabindweller]

PJ

I have allot of respect for you and what you are doing here. And couldn't agree more with your thoughts and feelings about doing things other people say can't be done. Coming from a very modest upbringing I was often told I would never do allot of things I have now done. Kenny and I have been Chewing some ideas over on a replacement for the 295/S piston. We belive there is hope there also. Hopefuly before to long we can prove one way or another what we got in mind will work or not work.

Jerry

[HoosierDeereMan]

PJ & Mitch,

How is this project going? Did you get the chamfer you wanted on the port edge? Since the index pin holds the ring stationary on the piston is it possible to chamfer the ring edge at the port window area as well to aid in the transition?

Troy

[pjr2011]

Update:

Last Friday, I took all four cylinders I have here to a friends home, where he has a nice, well equipped home machine shop on his back property. We locked the cylinder down in a fixture we quickly whipped up to hold them steady on the mill bed and used a 1/4" flat end mill to do the machining with. Since their is an arc in the cylinder port that we forgot to take into account when we first chucked everything up, we had to undo everything and reset our original set-up back onto a 360* turn table, which allowed us to not only machine along the X and Y-axis, but also rotate the cylinder to cover the arc of the port lip so the chamfer would be even all the way across.

We first machined a 45* angle on the leading port lip edge of approx. .035" wide and then made another cut of 20* of .010" wide on the tip of the "tear drop" to provide a smoother, multi-angle transition on the "tear drop" lip itself. (I'll post pics tomorrow, as my camera is at the office...)

I mocked up one cyclinder/piston combo and gave the engine a spin by hand, paying close attention to how the ring reacted at BTDC when the rod switched sides. It appeared to operate very smooth, even with a somewhat dry bore, as the thicker and wider second ring design of these pistons is far more sturdy than the original thin OEM ring. Even when the piston rocks in the bore as the rod changes sides, the ring is easily accepted and captured into the multi-angle chamfer of the port lip, which is a VERY good thing to see!

After seeing this, I'm even more convinced that this mod will work well in actual operation; however, the caveat to all of this is that the max cylinder bore diameter MUST be within factory spec for this to work well. If your engine clearances are way out of whack or if you have heavily worn bores, this mod probably won't be for you, as clearances outside of factory specs for this stuff make for a VERY sloppy, noisy, inefficent engine and will only aggravate a ring snag issue.

Building an engine properly to the correct specs goes without saying, but like anything else, it must be stated again anyway as a CYA disclaimer however, otherwise Murhy's Law will come-a-knocking on someone's door.