2M / 4M con rod differences

[palatine]

hey ToyMods,
After having my MS55 project sitting for a couple years, I'm finally tearing into this 4M I bought a year ago.

It was rebuilt by a machine shop and then left in someone's dry, warm basement for a long time - at least 15 years. It was all seized up with varnish-like thick oil, but I've got it spinning now.

So I'm looking at it, and it's pretty apparent that the connecting rods are from a 2M. The pistons are 81mm and new. Most of it looks new and gone through, but what is up with these con rods? It spins OK by hand. Were some 4Ms made with these rods? Did the machine shop screw up? (they're long gone.) Will it make a difference in crankshaft balance (but the 4M/2M crankshafts are the same, right?)?

I'm not sure what to do with this, or if it's even a problem, but has anyone seen something like this before?


(illustration from an old Chilton's book)

[crowncustom]

M,2M and early 4M ran the offset style conrod and the late 4M ran the standard style rod as whats in the 2nd pic and flat top pistons Im fairly sure the 2M and 4M cranks are the same.
Cheers Brett.

[palatine]

ah, this makes sense then, the pistons are dome topped, but would be the wrong size for a 2M. Thanks!