Reversed head swap question

[danval]

Yeah the first time the pistons come up and hit the head (which they will) boom goes the weasel. The i engines have domed pistons with matching domed combustion Chambers in the head, eta's have flat top pistons with matching flat combustion chamber in the head. Put a flat head on a engine with domed pistons and the first time you try to fire it, it will end badly.

Thanks. It's what I thought after looking at the chamber and pistons. It's just that you can't really tell by eye

[TobyB]

i always thought the dome on the B25 piston would hit the flat squish band on a 200/731 head. the 885 squish band is angled the same as the dome on the B25 piston.

Ayup. In a fit of boredom, I mounted an eta head on the mill and hemi'ed out the chambers
for the i pistons. The difference in shape is machined into the 885 head, it seems.
Drilled the oil passageways, too, for the cam.

Then looked at the ports again, set the thing aside, and bought a freshened head
from a friend for a couple hundred, and was much happier.

But it was a fun excercise in making a form tool. And flycutting valve seats by accident!

t