Here's yet another point of view...
GM started using the HEI on 75 models (earlier on some Caddies) because
they had to warranty emissions systems for 50,000 miles...and they
didn't want to have to change points for people. Also, point ignition
systems are marginal for an engine that is calibrated to run with
minimum emissions--lean mixture, EGR, wierd timing, etc. An HEI is much
more likely to work under these conditions, and as mentioned, any
misfires will heat up/damage the catalytic converter. Basically, GM was
playing it safe, and so HEI became standard.
I would sooner have a stock point distributor than a Mallory
anything...sorry, just my personal experience speaking. Others have
excellent luck with Mallory stuff, but not me!
Vacuum advance is there for fuel mileage...it advances the timing when
the engine is not under load, which improves efficiency and reduces
running temperature. In other words, it is a good thing, which you
ought to have. Racers generally don't want vacuum advance, because
racecars are designed to operate under wide open throttle, and what
happens under any other operating condition is unimportant. And, lots
of folks think that whatever is good for a race car must be even better
for their street car :) so the uninformed just do what the racers
do, and run mechanical advance only distributors.
GM used the big cap HEI on most engines from the mid 70s till the late
80s, but by then most were back to a small diameter cap, with an
external coil. But, these smaller distributors are used only with
computer controlled engines, so there is no advance mechanism in
them...fine for those who are going to put EFI on their engines, but
won't work too well with a normal carburetor.
I'd just love to see efi on a 235....I've seen it adapted to flathead
F*rd v-8s, which went out of production in 1953. I would think that it
would not be too hard to do, you could probably get away with only 3
fuel injectors, one per manifold runner. THe wiring and computer stuff
is available from many sources, with several of them allowing complete
programability.
Of course, fixing this modern electronic stuff takes a different
toolbox...I got to diagnose a problem on a friends 69 Vette last
night...we put an 86 Vette injected engine in it a few years ago, and
the throttle position sensor died. A couple hours of thinking and
testing, and a $40 part later, it was running fine. A Rochester on
barrel carb would probably have required a couple sharp raps with the
handle of a screwdriver to repair....
I keep a spare HEI module in my old trucks that I've swapped
over...because I've had a couple modules die.
Jim
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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