I am searching for +40 piston form my 1953 B31.
Or possibly some +30 rings if I can get away with just a hone.
Can I put a B31 piston form any year in or are some years incompatible with others?
Thanks
I should has added, do B23 pistons fit, would appear to be same size, but I am definitely no expert.
Thanks
B23 is a sidevalve engine so no valve pockets in the piston crown as needed by an ohv engine. That's assuming that gudgeon pin to crown height and resulting compression ratio is the same, which it may not be.
Best chance of a piston which will fit from a earlier engine is a piston from a B24/B26, same bore and ohv. From memory the gudgeon pin to crown height is the same but it's a while since I compared them...
All the standard B31 pistons are the same as unlike the B33 the con-rod length stayed the same.
i fitted a prewar piston to my b31 and runs ok. the top 2 rings are smaller thickness than later pistons by about 1/32" but i was looking for the low compression type anyway [ 6.75 - 7.1 ]. for higher compression i would go for a modern made piston personally.
Try these guys, FW Thornton, Telford.