In a message dated 1/29/00 9:24:40 PM Pacific Standard Time,
jforbes@primenet.com writes:
> 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
Ah Jim,
You're thinking somewhat along the same lines as myself for EFI on a 235,
but inorder to go with individual injectors (whether 3 or 6) would require
equal length and diameter tubes for consistant air velocity, I've been toying
with two ideas, one I think is quick and dirty, the other will require a
litte fabrication.
Quick and dirty:
Use a TBI setup from a similar cu.in. motor, the TB could be mounted in place
of the carb, and most likely an adapter would be needed for a proper fit.
V6's or newer I6's would be a decent donor car for the necessary hardware. A
custom EPROM can be burnt, eliminating all unecessary stuff (cannister purge,
VSS, etc.) for about $180.00 or so.
Doing it this way would have benefits over a carb and with the already good
lowend torque of an I-6, may be all that's needed. Benefits would be better
milage, altitude correction for richness, and better drivability in general,
but all in all you'd just have an electronic car.
Fabrication required method:
This is the one I've been drawing up in my mind, but would take a bit of
bucks to get started.
A muffler shop could bend up the tubing for the intake runners, AL. would
be best, but mild steel should work fine, probably need to powder coat it for
longevity or ceramic coat it, but cost begin to rise.
The shop could make all the runners meet into a squared collector to mount
the TB assy too.
Might have to go foreign, or Ford to get a 6cyl individual injector setup
for the ECM and stuff, but it's still doable.
The neat thing about this is that by tuning the intake runners, lower,
midrange, or upper RPM torque and HP can be moved around, long skinnt runner
promote lowend (not really needed on an inline motor) and short, fat runners
promote upper RPM flow.
I've been kicking myself in the butt for the past few years, I was at an
equipment auction once and didn't buy a hydraulic pipe bender that sold for
$85 or $90.00. I thought heck, I can always find another for that price.
Should have jumped on it.
I'm sure there's someone you can pay (and dearly at that) to design and
build it up from scratch, but I'd rather piece it together and make it work.
Myself and Pick-N-Pull have become good friend over the years.
Mike
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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