I'd like to get my hands on a couple/few '71 MGB heads (mate
to an 18GK engine). The specific model year/type is due to
racing rules that say that I may update/backdate only
"complete assemblies", and an engine/head combo is a "complete
assembly". Hm, does anyone have any magic spells to stop MGB
heads from cracking?
Don't overheat and don't overrev... Also, ammonia is
particularly damaging to non-stellite valve seats. (Hi Jeff!)
I've been told that the 18GK is probably
about the best MGB engine (note that I'll be balancing and
blueprinting this engine), partly due to its having full-floating
wrist pins; any counterviews out there?
The factory used the three-mains, but that's out of the
question.
Does anyone know of just how far down you can mill an MGB
head before you either breech a water or oil passage or cause
valve crash with a fairly stock cam?
Call me at home, Sam, I've got a reference to the MGB
engine that won E Production three years in a row. It
put out 145 bhp at 6500 RPM, using SU carbs.
I'm allowed to mill my
head down to rebuild tolerances, but if I can't find a specified
minimum head thickness then I'm just concerned with practicality
(as much as racing ever considers practicality, anyway!). I'd love
to be able to cut about .1 inch off my head to help the compression
increase a bit.
I'm pretty sure that Doane Spencer took .125 off the head
for the Hollywood Sports Cars MGB that won the title. (For
the record, it used to blow off E Types, I understand.)
But I'll look it up before you get out the grinder.
Preignition isn't too much of a problem, as
I can run up around 103 octane fuel, I seem to remember. Oh, yeah,
has anyone ever milled a head at a bit of an angle, so that the
greater amount of material is removed from the side of the chamber
that has greater volume?
Watch out for pushrod holes and valvetrain geometry, though
you've surely already thought of that. ALso, note that the
Weslake-designed combustion chamber is about the only good
thing about that cylinder head (please see my system name
before you accuse me of slander against the holy memory of
MG), and that unequal squish chamber is part of it. You don't
want to get rid of it -- it promotes such nice even combustion
and is part of the reason you can run Spridgets and Bs up
to about 10.2--10.3:1 CRs on street gas without detonation.
This would probably only be useful if a
limited amount of material can be removed (i.e., if a minimum head
thickness is specified) and you get to take the mean measurement
in the middle of the head.
I still say it's a bad idea. What do the rules say about pistons?
Can you use, say, Hepolite Powermax designed to give a 9.75:1 and
then mill the head/deck the block to get the CR right? The squeeze-
cast technology in these pistons also gives you the best of
both worlds -- cast and forged in one piston. There's a valve
hack that you can use, too...
--Scott "Why did I even *think* about racing something
other than an MG?" Fisher
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