Good heavens, Jon. You're certainly putting us to the test.
I for one am convinced your problem is not an ignition fault, and those who are
trying to convince you otherwise are shooting rubber bands at the moon.
It seems to me that if you're getting spark at all plugs, #2 cylinder is
firing, and the wires for #2 and #3 are diametrically attached at the
distributor, no matter what may be wrong within the ignition system, you *will*
get spark at the correct time to at least fire #3. (Somebody will correct me
if I'm wrong on this.) Add to that the fact that you've replaced so much of
the ignition system already, and you seem to have connected the other plugs and
wires in the correct fashion, and I can fairly confidently conclude that there
is no problem with your ignition system.
Your "Goldilocks" spark plugs go a long way toward reaching a solution.
Spark plug #1: "This mixture is too lean."
Spark plugs #3 & #4: "This mixture is too rich."
Spark plug #2: "This mixture is just right!"
Fuel delivery problem + fuel in float bowls = problem somewhere between bowls
and cylinders.
About the only things between the bowls and cylinders are the carbs.
Diagnosis: carburetion problem.
Prognosis: with a little carb therapy, full recovery.
Recommended procedure: Remove carbs and rebuild them.
A question, borne through the trees upon the most capricious zephyr:
>Rebuild them myself?
And the trees whisper a gentle "yes."
It's a cheap (I'm qualifying that one: cheapER than outright buying rebuilt
carbs), quick, easy, and satisfying job. I'd be thoroughly astounded if your
problem persists after a carb cleaning, rebuilding, refitting, mixture
adjustment, and synchronization.
>I have SU carburetors, I think they are HS4's, there is a metal # tag on one
>that says AUD135R.
Yep. AUD135 is an HS4 (the "R" means rear, front should have an "F"), but the
carbs on your 73 should be HIF4's, AUD550. Does this bring new light to the
problem? You betcha. The F!PO most likely scavenged the HS4's from a junker,
then fitted them to the 73 without benefit of rebuild. If the HS4's work
properly, is there any reason not to use them? Nope.
>Should I give up and get an aftermarket Weber (if a reasonably priced one
>exists?)
IMHO, properly set up SU's will work just dandy. The Weber downdraft is good
replacement for the later anemic single Z-S carb, and you don't want to fool
with Weber sidedrafts just yet, not while there exists the cheaper potential
solution of rebuilding the carbs.
An air induction leak somewhere? Likely, considering the F!PO removed all the
emissions control equipment. If you're certain all the ports on the manifold
are plugged, except the distributor advance line (it might even be a good idea
to plug that one temporarily) we'll move on.
An air leak at the manifold gasket? Replacing it when you refit the carbs
after rebuilding couldn't hurt.
>let's imagine that the forward carb is plugged and
>the back one is spitting out mostly gas. This fouls 3&4, then 2 draws across
>the bypass tube and gets just enough gas to run, but there is none left for
>#1?
Yowza! That's something that might not have occurred to me. It's so crazy,
it just might be true! Remove the air cleaners and listen at each carb inlet
(especially the front) for the hiss that characterizes air flow. A length
of small-diameter hose, one end held at the inlet and the other at your ear,
will help. Or you could clamp off the fuel line to the rear carb and see if
the engine quits. (Come to think of it, that would be the first thing I'd try,
even before rebuilding the carbs.)
Besides the carbs, the only things I can conceive would be wrong would require
stripping the head off to check or fix, and we'd rather not do that just yet.
>Sorry to rattle on so long about this, just trying find the best course of
>action...
We won't necessaily recommend the *best* course of action ;), but dammit,
we'll get your car running.
--
Jay Tilton
jtilton@vt.edu
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