Hey Glen... I may just have a dist. for you we could swap even up.
I just went through this with my 75 Spit. As purchased, it had the 45D4 (??)
that has
vac retard and the elec. box is bolted right to the side of the dist. (as
opposed to the firewall
mounted electronics box) The old elecs are long dead (of course) and it has
a Pertronix Ignitor in there.
I just switched from the single ZS to twin HS4's. So I went through the whole
ritual of testing
every variation of vac connection., advance curve tests, and every convolution
thereof !
In playing with the two different distributors. I had (1-vac adv. 1-vac
retard) , I found two different
mechanical advance limiter plates. The vac retard was limited to 6 degrees (12
at the crank)
while the vac advance unit was limited to 10 (20 at the crank)
I also found the reason my idle floated around was a leaky vac retard unit.
It would only hold position with >10 pounds of vacuum.
below that (which would equate to hard acceleration) the vac. was leaky and
would not
maintain position. Using a hand held vac. pump I could watch it simply 'return
to home'
as such. As soon as I released the vac and it bleed down around 10 psi of vac.
It would just all
of a sudden start loosing all vac and head for zero within 1-2 seconds. I had
to pump it
up quickly to get it past 10, then I could control it.
anyway.... Do to the extra tang that bolts the vac retard to the carb body,
we'd need to
swap the dist. bodies. Something else to check before you rearrange all this
stuff on your car.
Look carefully at the BOTTOM side of your ZS carb throat. You may have a vac.
port coming
out the bottom of the carb just like it does on top. One is ported vac, one is
not.
My '70 GT6 had a dist that had both an ADV and a RETARD vac port on the bellows
on the
distributor body. One tap went to the top of the rear carb, the other the
bottom of the front carb.
I guess it was kind of a TUG-OF-WAR for finite instant positioning.
I'm staying with the vac advance I just bolted onto it, but I'm swapping all
kinds of inards and
mechanical advance plates.
If you want the vac retard unit, I can mount it on the proper dist body, with
all the proper
parts (as this is actually and extra dist for me) The bearings and etc are in
fine shape
and I'd end up with a usable extra advance pot.
....something to think about.
Paul Tegler wizardz@toad.net http://www.teglerizer.com
----- Original Message -----
From: "Glenn Trunnell" <trunnell@earthlink.net>
To: <spitfires@autox.team.net>
Sent: Tuesday, August 15, 2000 2:09 AM
Subject: Distributor vacuum advance again
After reading the discussion about this topic last week it occurred to
me that my vacuum advance may be at the heart of my problem. My car
runs great everywhere except at idle. I have a '76 Stromberg and a
vacuum advance distributor, I know without a doubt that this is in fact
a vacuum advance unit instead of a retard unit. I currently run with
the timing set at 12 deg. btdc with the vacuum advance line
disconnected. This gives me good off the line acceleration, but
requires that I run the carb very rich to keep it from missing at idle.
If I connect the vacuum line I get something like 20 deg advance at idle
which drops off as soon as I hit the throttle. I believe that the ZS
carb I am running is in fact designed to run with the retard distributor
rather than the advance unit I have. If I retard the timing the idle
smoothes right out but the car will not accelerate at all,. Does anyone
know of a source for the retard type vacuum actuator or have one that
they would like to sell? I would really like to have the smooth idle
and be able to lean the carb out and I think this may be the solution.
Thanks,
Glenn
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