The fuel pressure at the carb is a function
of the carb. spec. while the pressure TO the carb is a function of what the
motor requires (state of tune) to keep bowl level up to spec. (flow rate) for
correct mixture under greatest demand (up a hill or flat out in high gear under
WOT over time), which depends upon engine state of tune.
Fr'instance....there is a guy on this list who
complains that while the motor revs easily
to 5K+ in the lower gears, it won't go over
70 is high gear.
Concurrently, the plugs burn LIGHT tan.
Now as we know, most fuel problems are
electrical! :):)
And I am not saying I KNOW what his problem is. 'Cause I don't.
SU's and Webers like low pressure at the
carbs. = 1.5-2.5. And with the stock motor
or mild state of tune, an LP (4psi) Facet will
do the trick. Unless the pump has seen many miles and is worn and
on the way out. Then it might be fine in
the lower gears (if high rpm's not "held")
but not be quite up to flow rate in the
higher gear(s) under high load (WOT
going up a hill) over (greater) time.
Another way to say this:
The fuel "demand" requirements of
my PO'd Vizardized 1340 (90HP @ the rear wheels) required the Facet HP pump
(6-8psi) to avoid running lean in the higher gears at WOT (over time) with a
press. reg
set to 2.5psi at the carb (Weber 45 DCOE).
Generally....
plugs should be more toward a "brown"
(rather than "tan") with a tinge of black
(carbon) on the "outside" for a mixture
meant to produce "best power".
Sidebar: to "quiet" a Facet pump:
use a bit of rubber between the Facet pump
and the car body as an insulator to absorb and quiet the Facet's operation.
Cap'n. Bob '60 :{)
|