Dave,
I have some experiences to relate regarding the ZS/Spitfire combination. It
may or may not help you:
> The Zenith Stromberg carb on my Spitfire is giving me a lot of trouble.
> Idles speed fluctuates between 1000-2000 rpm and it is running too rich.
> I've tried adjusting it but it does not stay in tune. I eventually gave
What year are we talking about. I'll assume that it is a 1500. If this
is the case, what is the status of your emission control equipment? The
smog gear in my car (a 1500 with the Mk4 1300 motor) had been removed by
the PO (previous owner) and the car ran like you describe. I had some
of the bits on-hand from a parts car and did some experimenting.
Basically, it helps to have the smog gear in place. I tried various
combinations of tubes and charcoal canister until it ran somewhat
better. I could never get it to idle below about 1500rpm though. I
ended up putting in the ZS carb from a 1970 1300 motor which has no
inputs for emission control plumbing and it now runs pretty well. The
1500 had even more emission stuff than the Mk4 so your case could be
even more complex.
> mechanic said that the Stromberg does not take rebuilting very well and
I rebuilt the '70 carb and it seems to be working well. Not GREAT, but
well. I think part of the reason that it is not working GREAT is that
the throttle shaft bushes are worn, allowing air to come in around the
throttle shaft. This is supposed to be a common problem with both the
ZS and SU carbs and it prevents the proper tuning. The way I understand
it, the increase in air coming in will cause the need for a richer
needle setting at idle (the air leaking in is a larger percentage of the
total airflow). At higher revs, the air leak is a smaller percentage of
the total air flow and the mixture becomes rich. A number of places
will put new bushes in for around $200. But aside from this, I think
the rebuild was an improvement.
> suggested to replace the carb, he basically said I have three choices; get
> a used SU carb, get a used dual SU carbs set, or go for a Weber conversion
> kit. Needless to say all three choices are more than what I can affore
> right now and a Stromberg rebuilt kit is only $13 from Special Interest.
I would suggest doing the rebuid for this price. If it doesn't help, you are
only out 13 bucks. But if your emissions stuff is not in place, you may never
get this carb right. Then your choices are to dig up the EC plumbing, or
follow your mechanic's advice and look at replacement carbs.
I hope that this helps you some. I would be interested in hearing about
what you end up doing and how it comes out.
Good luck,
Mike
mburdick@unmc.edu
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