Can one Convert a 11mm head to a 12mm head?

[Familydiesel]

I have a question I haven't found an answer for.  Can an 11mm head be converted to fit on a 12mm block?  I'm talking about a mechanical head to mechanical block conversion.  If so, what needs to be done so it will bolt up?  If not, why not?  Anyone done it?
Thanks,
Greg

[maxfax]

I've heard rumors of this being done..  Supposedly all that had to be done is measure the existing head bolt holes (all of them since the one is a bit larger for oiling) and then drilling them 1mm larger than their existing size... Never actually talked to anyone that has doen this though..  You'd have to clamp the head down in a drill press I woudl think so that you can be sure the holes are drilled absolutely straight...

I would assume that with taking such a small amout of metal out ot the holes that the head wouldn;t be weakened severely or anythign like that..

[Familydiesel]

Aren't the 12mm bolts longer also, which would either mean they are tapped deeper into the block and/or the head area is a bit taller?

[subsonic]

Washers are different as well, recesses need to be opened up a bit.

[Fisher]

I've done it lots of times.  You need to drill out the 11mm Bolt Holes and enlarge the washer space.

On a 12mm Head the Bolts hang below the Head Sealing surface 1 1/4".

For use in the 11mm Head I cut the washers off of 12mm Bolts and use two (2) 11mm Headbolt Washers, this gives you very close to the 1 1/4" you need for the 12mm Block.

I've taken apart a few Heads that had thick hardened Washers on them, similar to the thickness of the 2 Washers.  This was probably a more common practice at one time.

[Fisher]

Correction:  You don't need to enlarge the Washer space when you use the 11mm Washers.