> Why did you replace the carb?
I had several reasons for replacing the Z-S with HS4s.
1. They look cool.
2. I expected that I would get more power.
3. The fast idle pin on my Z-S had melted so I had no fast idle,
even though the automatic choke did work.
4. With the original carb setup, when I stopped at a light after driving
at high speed for 20 minutes or more, the engine would shake for
several minutes before settling in to a smooth idle.
Interestingly, from reading on the subject, a good bit of the
performance improvement from the carb switch comes from
the more efficient exhaust manifold. The stock pre-1974
exhaust manifold is really a long center branch header.
When I made the conversion, Scott Fischer wrote a long
disseration explaining how the momentum of the downstream
exhaust pulses provide a partial vacuum to extract the ones
which followed. Some of you may remember his sausage
analogy.
In any event, I did notice a _significant_ increase in torque
at about 2500-3000 rpm after the conversion.
As far as tuning is concerned it is quite straight forward if
you have a Unisyn and follow the procedure in the manual.
I tuned mine when I installed them 2 1/2 years ago and just
retuned them last week. Aside from that, the only time I
touched them was to lean them out to get past the New York
State emmissions inspection. (Yes, the car _does_ pass
without the catalyst.)
Peter Schauss
pschauss@aol.com
1980 MGB
1963 Austin-Healey 3000 Mk II
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