HEI was first used in all 1974 in the Calif. models. That Caddy must have
been a Calif. emissions equipped car. New Mexico Jim
J Forbes wrote:
> 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
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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