At 05:56 PM 8/16/98 -0400, Bill Schooler wrote:
>.... Discovered a big difference in how you set the MGA carbs relative to
the process for an MGB. Specifically, the manual tells one to "disable"
the front carb by closing the throttle plate and raising the piston about
1/2 an inch, then start the car and run it on the back carb alone,
adjusting it by the tried-and-true method of lifting the piston a bit and
checking the response.
>
>Don't have any trouble with the process of lifting the piston, but am a
bit puzzled about disabling the front carb. Not so in the MGB world.
Then, of course, after getting the rear carb tuned properly, one is
supposed to disable it (!) and go at the front one in the same manner.
Only after each of the carbs has been adjusted while running the engine
alone, does one bring both into play. Is this for real? Or is the MGB
process better?
Yes it's for real, and "better" may be a little subjective. For someone
handy at the proceedure, the method in the MGA manual may take 5 minutes
rather than 3 minutes, but for someone not so familliar with the
characteristics of these carbs, you're more likely to get the mixture right
on the first try.
There is a balance tube in the intake manifold that allows all cylinders to
share the intake from the carburetors at slow speeds. Because of this, if
one carb starts out running very rich , you will at first be adjusting the
other one quite lean to get the best idle, but even then 2 cylinders will
run rich and 2 will rich lean. It may take a few itteretions of switching
back and forth between the carbs before you finally get them both with the
same otimum mixture.
With the method in the MGA manual, you disable (completely close) one carb
while adjusting the other, so you can get the mixture correct with the
first adjustment, just like as if it was a single carburetor engine. This
is particilarly helpful if the carbs are pretty far away from the correct
mixture to start with, such as if you are firing it up for the first time
after having just rebuilt the carbs.
Barney Gaylord
1958 MGA with an attitude
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