z134 engine rod bearing tolerance

robm552018@gmail.com · Apr 17, 2023

My tractor is an industrial MH-50 loader tractor, 1959.

I'm in frame overhauling journals and installing new bearings. My gap is about .005. The book I think states max tolerance is .003.

My engine started to cease up when the oil pump went out, I think was the cause. It spun 1 cylinder rod crank bearing and it laid some soft bearing metal on the journal. Other journals look good. and the mains look good. I sanded by hand the journals and its took hours with 600 grit emery cloth on #1 but it turned out pretty good for a low tech method. I don't think I'm out of round more than 1-2 thousandths. I turned the crank often systamatically while sanding to keep it round.

Is the tolarance of bearable? I really need to use my loader and then this summer may do a better rehaul. The problem is machinists and mechanics in my area are out months and some even close to a year. We are the heart of farm country here. so its up to me.

Dieseltech · Apr 18, 2023

The best way I've found to remove aluminum bearing material from crankshaft is muriatic acid from the hardware store. Use OUTSIDE, as it will take your breath away using
a small paint brush to apply the liquid and melt the aluminum off the crank journal.

M-MAN · Apr 18, 2023

An extra two thousandths ain't
gonna hurt for a while on a low rpm
tractor engine. You didn't mention
resizing the rod. Anytime you spin
a bearing it's going to damage it's
housing whether it's a rod or main.
If you don't address that you'll
have a rod knock soon. There's a
good chance it will lock the engine
as soon as you tighten the cap.

ptfarmer · Apr 18, 2023

(quoted from post at 19:52:58 04/17/23) My tractor is an industrial MH-50 loader tractor, 1959.

I'm in frame overhauling journals and installing new bearings. My gap is about .005. The book I think states max tolerance is .003.

My engine started to cease up when the oil pump went out, I think was the cause. It spun 1 cylinder rod crank bearing and it laid some soft bearing metal on the journal. Other journals look good. and the mains look good. I sanded by hand the journals and its took hours with 600 grit emery cloth on #1 but it turned out pretty good for a low tech method. I don't think I'm out of round more than 1-2 thousandths. I turned the crank often systamatically while sanding to keep it round.

Is the tolarance of bearable? I really need to use my loader and then this summer may do a better rehaul. The problem is machinists and mechanics in my area are out months and some even close to a year. We are the heart of farm country here. so its up to me.

Did the bearing spin in the rod also? if it did the big end is out of round on the rod. The rod would either need to be resized (any engine machine shop should be able to do that) or replace the rod with a known good one.

The Ferguson TO35, and F40, the Massey Ferguson 35, and 50, also had the Z134 engine so if you can find one of them that have been parted out you have that option.

If you can find MF part number 1750186M91 (rod bearing) is -.002" undersize that is made for slightly undersized rod journals (I haven't been able to locate one).

If you can't find the undersize bearing you will need to shim the relief spring in the oil pump slightly to make up for the oil pressure loss from the loose journal.

z134 engine rod bearing tolerance

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