model b pistons questions

[warren woodrow]

Finally got pistons out of my 1941 model B . Serial # 102048 . I have one bad cylinder which I believe will require a maximum overbore . Is the maximum .125 and is that 4 11/16 inches . Some on this board have said that a late model B piston will fit .125 overbore and pistons will fit my rods and pins . Is this all correct as I am ready to take it to a machine shop.
 

[Mike N Mo]

A 1941 B would have had a stock bore of 4.5", so a late B standard bore piston would require an overbore of 3/16" (4.6875"). This should work ok unless the block has excessive rust pitting on the water side of the cylinders. I've read on this forum that .125" over pistons (4.625") aren't available for the early styled B's, but I've never researched that myself. Just passing along the hearsay. I think I would have the pistons before having the block machined. You can always return the un-used new pistons, but you can't undo the machining done on the block. Good luck with your project. Mike
 

[gtx1967jewison]

These things have alot of iron in them. As an example, no pistons are available for a model R so they are often bored 375 thousandths! Thats 3/8". To use 720/820 pistons. I would call Ray at Extreme Tractor Parts or Josh Blackburn. They both have built alot of these & both make custom pistons. I believe you can use Late B pistons. Get some new aluminum ones. They are both on the pulling forum often.
 

[MSD]

Can you reuse the old pistons or do you have something else in mind? It might be cheaper to sleeve it and use the original pistons than boring it and putting new ones in. Last A we did it was $50 for the sleeve installed plus boring charges.
 

[warren woodrow]

Had been led to believe sleeving was alot more expensive. I think my pistons are good and at that price range I would rather sleeve and use my originals.
 

[warren woodrow]

Machine shop I contacted said $700.00 to sleeve and bore both cylinders. Needless to say I will contact others. Always someone wanting to make a killing....... instead of a living.
 

[gtx1967jewison]

New ones are half the weight, more compression/power, barely more than the cost of rings for your worn originals. To sleeve it requires boring much farther than it does with new pistons. Its always cheaper to buy pistons & bore than buy rings bore sleeve & finish bore the sleeve. & a much nicer outcome imo.
 

[JD Man MI]

Use late B pistons, I've done it and it works great