Message text written by INTERNET:sbollen@att.net
>You are kidding, right?? On an SU carb there is one needle and one jet. On
a
Rochester there are metering rods, accelerator pump shooters, power valves,
numerous jets which all have to be sized correctly. Same ids prety much
true of
the Holley. Then there are all the tiny passageways that can get clogged. I
have
rebuilt al;l four types at one point or another and I 'll take the LBC
carbs
anytime
<
Not all Holley's have metering rods but I did forget about the power valve.
The short story is that the fixed venturi is a less than optimal situation
and all these things (power valves, metering valves, emulsion tubes) are an
attempt to patch around the fact that the depression at the venturi is not
linear with the air flow. It is a compromise. But it has the advantage
that once the correct parts are determined (after many hours on a flow
bench and dynomometer) setting one up for a particular model is pretty fool
proof: just put in the specified jets, emmulsion tubes, metering rods, etc.
No fine tuning required.
The variable venturi carburettor, on the other hand only requires a tapered
metering pin and some fine tuning. No power valve, no idle circuit, no
idle to main jet transition problems. British Ingenuity at work.
Dave
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