KH vs. MC engines

[Lines Peter]

I noticed a couple of posts regarding these engine types, so I thought I'd
contribute what I know...
I'm in the middle of a 4kq turbo project and actually have both KH and MC
('86 vintage) engines apart right now.  I'm speaking strictly about the
engine itself in this post.  There are obviously numerous differences to the
engine management system, I'm not going to get into that.
The KH is 79.50mm bore nominal, and has cast 8.3:1 CR pistons.  The MC is
81.00mm bore, and has forged 7.8:1 CR pistons.  The compression ratio
difference is due to the size of the bowl machined (yes, machined!) in the
piston crown.  Both engines have the oil squirters and the MC pistons will
work in the KH block if it's bored out to 81.00mm.  The MC has a special
freeze plug to allow for coolant return from the turbo and a different
coolant port bolted to the head to allow coolant flow to the turbo.  Both
parts could be interchanged if needed.  The MC includes a plastic oil baffle
in the pan that is also interchangeable.  The MC and KH cams are different
grinds but are physically interchangeable.  The KH (the one I have) was from
a slushbox car so it had a flexplate.  The MC flywheel will bolt-up to the
KH crank with no issues although the timing pins for the engine management
should be verified to be correct first.  Someone mentioned an oil pump
difference, but I find no differences in the parts I have.  Hopefully this
info will be useful to someone... The world needs a few more fast 4kq's!
Cheers.

Peter Lines