What follows is my OPINION on the matter. I would be interested in hearing
yours
:-)
On 4 Jun 2005 at 0:09, James J. wrote:
> p.s. Does anyone know if the Iron Buick 300 heads were cast from the
> same molds as the aluminum ones?
Nope. Different molds, very different manufacturing process, even different
shrinkage as the metal cools. The aluminum parts were cast with the molten
aluminum under pressure, the iron parts used the same old gravity-fed
sand-cast
techniques that had been used for 100 years or more, and the molds reflect
these
manufacturing differences.
How similar they might be, I really cannot say with any authority, but they are
definitely not the same.
I'm afraid that the only way to truly get your questions answered would be to
cut up
an aluminum head that has the same casting number as the heads you want to
port.
Either that, or just grind conservatively and pray. (that's what I do) :-)
My experiences and those of friends who have tried to do a home porting job
show
that you can actually get some pretty reasonable gains just by matching the
ports to
the intake and exhaust manifolds, doing some very minor clean-up of the
runners,
and swirl-polishing the valves, but it's real easy to make a set of heads flow
worse
than stock (rendering them useless) if you get too aggressive, unless you have
a flow
bench, and lots of experience.
If you try to stay within the bounds that I outline above, there is no danger
of hitting
the water jackets. In other words you want to just clean-up the casting flaws
and
maybe blend in the transition between the seats and the pockets under the
valves,
and possibly thinning, blending and shortening the guides, without actually
changing
the shape of the ports at all. Any more than this should be left to the experts
who
have already ruined a few dozen heads.
BTW, I'm certainly not an expert, but I have worked a few heads, admittedly not
these heads, but several sets of Chevy small-block and big-block heads, my
Jaguar,
and even one Ford flathead block. I'm currently working on a set of Buick 215
heads
for my own V8 conversion.
One other bit of info that might be useful to someone working on a set of Olds
heads:
Unlike the Buick and Rover heads, which are a rather different animal, (the
Buick is
the a better design in my opinion because the spark plug is closer to the
center of the
combusion chamber), the Olds heads are very similar to the small-block Chevy
heads of the same era. So it would stand to reason that they _might_ respond to
some of the well-documented porting tricks for Chevy heads of the mid 60's,
such as
un-shrouding the intake valve on the combustion chamber wall from the side up
to
the spark plug. Just a thought. There were several articles per year back in
the 60's
describing how to modify Chevy heads... with pictures.
Marvin
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