Big Block parts interchange


New member
I picked up some engines in hopes of building one.

I am pretty sure they heads from a 340-390 will fit on a 240 270 block.
But I am pretty sure the chamber volume will be different so there is nothing there to gain ( and plenty more to lose )

Case covers I am pretty sure they look the same but one has bearings for the balance shaft and one does not.
Can you still interchange them?

Strokes are different but are the rods interchangeable?

What about cranks can I make a 240 stoker?

Are the big block kind of like the small blocks and you have a different deck height from the smaller ones to the larger ones?

Thanks in advance for any information

Brian B.

New member
Crank journal sizes are different so i do not believe you could swap the side covers but thats based only on what i read~ i dont own a GX270

Cranks are not interchangeable

Gx240/270’s weigh less, much less than the bigger brothers, stroke is like 58 vs 64/66/69mm etc etc~ so i imagine yes shorter deck height

Go to ARC& look at the rods, i believe the rods do not interchange, or at least they are different lengths.

Two entirely different families of engines,.. yes cams share same cam, but other parts dont swap over at all.

Its a red head step child