Farmall A Piston Question

Mr. Jeffries · Jan 16, 2009

Hello,
I have a student working on a Farmall A tractor. He ordered a replacement piston as he had one that was cracked pretty badly. The tractor has stepped head pistons in it with 3 compression rings and 1 oil ring.
The replacement piston that we ordered seems to be the correct size (bore and pin) but it only has 2 compression ring grooves and 1 oil ring.

Will this work on in this application? I"m guessing the weight difference would be minimal.

Thanks for any help,
Jared Jeffries
Jasper FFA Advisor

Anonymous-0 · Jan 16, 2009

don't guess on the weight!. Viberation can occur. Why not change them all ? How about getting them ballanced?

RN · Jan 16, 2009

Weigh the piston assembly if you"re worried. The 4 ring design is "early" design, the 3 ring is "late" design. Later rings will be slightly different than early but 3 ring is more current. piston skirt length should be close to same, wrist pin to top of piston should be same, oil control ring may be wider, multipiece insted of plain or narow space multipiece. Ford tractors have same situation, balance problems with mixed 3/4 ring pistons is not noticable. 3 ring piston might have a little more blowby on worn cylinder but pressure of 120 or so is not going to be much. Diesel pistons are more of a concern- the 4 rings are needed for 250+ pound cylinders. RN

Jonathan Mirgon · Jan 16, 2009

I would either replace all pistons and rings with the same type piston and rings from the same manufacturer, Or if just doing a patch job to get it running again buy a used piston assembly off of e-bay or another source that matches the three that are in it currently. I dont think mismatched pistons and or ring assemblies are the ansewer to a long term fix. Whichever route you go , Good luck with your project.

Ed pap · Jan 16, 2009

Hello Mr Jeffries,
If the new piston is a stepped head and it is with in 1 oz of the other pistons you will be fine. when you assemble the motor check the piston clearence to the block at TDC of all the pistons if they are the same you are good to go.
If you want to go by the book then I would change all the pistons and rings.
Good Luck Ed
abcrepairparts

Farmall A Piston Question

Mr. Jeffries

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Anonymous-0

Well-known Member

RN

Well-known Member

Jonathan Mirgon

Member

Ed pap

Member

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