Well, we're arguing nits here, but ....
re: " Using the throttle butterfly, you have issues of throttle linkage,
dissimilar metals (brass, aluminum & steel) and fast idle screw wobble."
I submit none of these are a factor, since at idle the throttles are stopped
(on my car) by the throttle stop screws. The linkage is not in play--except to
pull the throttle shafts to the stops--nor is the fast idle screw (there should
be some clearance between the fast idle screw and the cam at idle) and any
metal dissimilarity is insignificant (if you set everything when the engine is
hot--like it'll be when you're driving--differing metal coefficients of
expansion are automatically compensated for).
I don't like the idea of the two strong throttle return screws slamming the
throttle plates shut in the (soft aluminum) carb throat--I believe you'll wear
a groove eventually. I also prefer to idle a little faster, so I'm getting
electrical power from the generator and not draining the battery (with a
generator, at least with mine, you're running off the battery until around
650-700rpm).
bs
--------------------------------
Bob Spidell - San Jose, CA
Bob -
Controlling idle speed with the screw is very simple - it is a narrow
valve that is highly stable, controlled and consistent.
Using the throttle butterfly, you have issues of throttle linkage,
dissimilar metals (brass, aluminum & steel) and fast idle screw
wobble.
On my BJ8 once I set my rebuilt carbs to factory spec and idle through
the slow idle port (and fully shut throttle plate) it has maintained a
perfect and constant 550 rpm idle for over 40K miles without so much
as a touch from my screwdriver. Of course I put in a pertronix kit
which made a huge difference too.
Strangely enough, the carb failed because the jet diaphragm finally
went, but I didn't touch the carbs for more than 5 years of almost
daily running.
The carbs are very well designed if set up factory spec. The little O
rings on the slow idle screw are the key to the success of a proper
tune.
Alan
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