1938 John Deere L piston skirt

Countrykid66 · Jun 28, 2017

Hey everybody, I'm in the process of restoring an old John Deere L tractor and I'm having the engine bored out and worked on. It's one of the Hercules engines, the NXB type I do believe, and I'm trying to figure out how much distance there needs to be between the piston and cylinder wall. I didn't know if it was 6 thousands over or 4 thousands. Anything you know about these engines will be greatly appreciated. Thanks

J. Schwiebert · Jun 28, 2017

Cast or aluminum pistons?

RWT · Jun 28, 2017

The clearance is built into the piston. I don't think I have seen a case were this weren't true and I've worked on a lot of motors.

Generally you finish the cylinder at whatever oversize the piston is. When you mike the piston it should be the amount of the clearance smaller than this number. Sometimes I would take the cylinder over a little if I thought it needed it but I am talking like 1/2 to 1 thousandth.

I remember NXB's being 3.25 bore. I would bet the clearance is closer to 2 to 3 thousandths than 4 to 6. But I would have to mike the pistons to give you a better answer.

For what it is worth I have ran an engine machine shop for a few years until I burned out. I still overhaul motors for people.

RT

Gambles · Jun 28, 2017

Did you mean cast or forged pistons? Or did this engine have some rare cast iron pistons?

LarrySTN · Jun 29, 2017

Gambles, many early engines had cast iron pistons, this was before forged aluminum was available. John Deere used cast iron pistons in their A B D & G for years. Cast iron pistons were not rare. My forgetter works way too well to give you a list of the engines I have been around that used cast iron pistons. Yes they were/are heavy. I have at least one unsyled B that still has it's original cast iron pistons. It runs well.

Countrykid66 · Jun 29, 2017

They are aluminum pistons. What is going on is that when we took the engine apart, there were so pretty bad pits in the cylinder walls. So we bought newer pistons and first bored it out. Well the bore still didn't take some of the pits out so we decided that we were going to try to sleeve it. Well now the piston just barely won't fit down into the sleeve so the machinest is trying to figure out how much to bore out the sleeve to make the piston fit just right.

DGinVT · Jun 29, 2017

I did the same job about 20~ years ago. I bored out the block and made new aluminum pistons to fir. Works well and still runs today. I did put on a Wico "X" Magneto which is, in my opinion, better than the "C" magneto.

Countrykid66 · Jun 29, 2017

yea it came with a wico mag on it so we are having it rebuilt and put it back on

JOCCO · Jun 29, 2017

I did put on a Wico "X" Magneto which is, in my opinion, better than the "C" magneto.

THATS FOR SURE!!!

1938 John Deere L piston skirt

Countrykid66

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J. Schwiebert

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RWT

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Gambles

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LarrySTN

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Countrykid66

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DGinVT

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