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JOhn deere B pistons size 4.705 ?

N

newJd4430

Member
i have a set op pistons for a john deere be with no
stamp on the top of them to tell the size they measure
4.705 is that standard bore or oversize part number is
A1239 any advise would be greatfull
 

For the Late "B" and even into the 520/530, the Standard Bore is 4.68"
Yours must be an oversize...maybe around + 0.010"
 
What does the bore measure? .045 over should be 4.727 so if your measuring is right they are .o22 too small. Are you measuring across from the pin at the bottom or up by the ring grooves?
 
As per your last post I said you measure pistons down at the skirt at 90 degrees opposite of the piston (wrist) pin. This should be the largest spot on them you can measure.
I ask once again are they cast iron or aluminum pistons ?
 
ok i measured it how you said an it came out to 4.7225. now how do i come up with my size with that measurement this is my first time so im learning
 
Here is how I am figuring it and I do think it is correct.
std size is 4 11/16 " which is to be 4.6875 now add .045" for an oversize and get 4.7325 now that is the BORE SIZE. Now you need clearance so for an aluminum piston lets go with .010" (cast iron would go .006" )so deduct .010" from 4.7325 and I get EXACTLY what your piston measures 4.7225

So I say you have .045" oversized pistons for either a late B or 50 or even 520-530 ? depending on what they look like. If the tops look good and not corroded ? it seems strange there is not a marking on the top of them ? Maybe they are corroded or been ground on ?
A 50 would usually have thinner piston rings than a B and a 520-530 IIRC have a dome shape on top.
 
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