In a message dated 2/20/2006 5:31:55 PM Eastern Standard Time,
downing.j@sbcglobal.net writes:
Lynn; Today I got to looking into the Weber
48. It has a 180 main, 160 air correction and F-7 emulsion tubes, with
42 mm chokes. Are these figures in the ball park. Looking at the
answers you have sent me, its close.
I really have no exact answer for that one. We have all kinds of tricks
done to the carb to get Max flow at over 9,000 RPM. So our booster signal is way
below what a stock booster or auxiliary venturi would generate. So, a 210 main
and an 80 air is meaningless.
A bit over 12:1 FA is just right, and that should read 1500 EGT at
6,500 RPM. A Bridgeport 12A will do 173 HP at those settings. A street
ported 13B about 180 HP.
Try to stay below 1650 in any case. Start with what you have and see
what static RPM it will pull. Then just tune it from there. Spark at 25 degrees
is plenty. Richer / leaner overall is the main jet size, and richer/ leaner
at the top RPM is the air corrector jet. Smaller jet is richer.
Bigger jet is leaner.
Also the springs are set up to close the
carb if the cable becomes disconnected. Do you remove these and
use an external spring to keep the carb open or
is there some way to turn these springs around. Thought I had better ask
before I tear into it.
I have never looked at this. I would think that removing the stock spring
would be easy enough. Then the pull open spring could be very light. This sounds
like an area where ground only and flight only should be two different items.
Uncommanded full throttle on the ground could be more excitement that you can
stand.
Another question is, do I need a regulator for
the Carter electric fuel pumps. Jegs has one by Quick Fuel which has a
bypass feature and it says that it is for steady output electric fuel
pumps.
Yes, a regulator is required. The Weber needle and seat, will work OK up to
about 4 pounds, then it will overpower the float and start dripping out of
the boosters. We use a Holley but many good ones are available. We use a 350
Gross jet and 6 pounds just to keep enough flow at 9,600. We don't care if the
boosters drip. We don't use the engine below 7,600 RPM.
It looks like next winter I can install two
high pressure fuel pumps and just flip the low pressure ones off and
switch the high pressure ones on and use the Weber for the throttle
body. I will need to machine two ports for the secondary injectors
and weld them on the intake manifold. Does this sound like a
viable solution for a duel fuel
system?
Yes.
If there is time allowed to use up the float bowl
fuel before injection starts.
The Wittman Tailwind I'm building has a 34 gallon
fuel tank in the cowl which flows down to a gascolator, then into two fuel
pumps, which are lower than the gascolator, then pumped up to the
carb. Thank
you. JohnD Working on
systems between cowl work.
I will be doing the dual fuel Weber on mine as well.
Lynn E. Hanover