BY RICHARD EHRENBERG. Copyright © 2005 Richard Ehrenberg. Reprinted by permission.
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One ongoing problem with our Bold Beeper project was carburetor related.
On the dyno, we had run a Holley
950 HP double-pumper, and it had performed
flawlessly. Since we had misgivings
about the true streetability of a double
pumper, we had fitted a Holley Avenger 830
CFM vacuum-secondary for street use,
where it worked OK. However, with the tall,
sticky French Drag Radials installed, no
matter what we did, the car would fall on its
face about halfway through first gear. We
diddled the secondary springs, pump shot, etc., until we were blue in the face—to no
Finally, with our new AEM wide-range O2 display installed, we were able to do
some scientific testing. This affirmed what
we suspected—the engine was leaning out.
Normally, this would point to a fuel pressure
drop, but the car pulled cleanly in the higher
gears—even at top end—situations that
would seem to place even greater demands
on the fuel supply. The fuel pressure
gauge didn’t even wiggle!
That left the
carb as the culprit. Not that it was defective—
far from it. It was just mismatched,
tuning-wise, to our hot-cammed, big-cube,
tight-converter, tall-geared oddball setup. And, we were running out of patience.
As we were busy pulling out our few remaining hairs, we glanced over at the
double pumper, resting comfortably under the bench. Could it be used on the street?
Hmmm. We reviewed the myriad reasons why we had discounted it in the first place:
A quick call to the carb-trouble “go to”
guys, the Vrbancic clan at the Carburetor Shop in Ontario, California, gave us the
impetus we needed to think outside the
box. The C.S. guys said that adding a
nipple for PCV, and a ported spark fitting,
was no big deal (easy for them to say.) They
also indicated that they could lengthen the
duration of the pump shot to improve
kickdown performance, and that all that
would be required to run on the street
without the choke was a few pumps of the
pedal and maybe 90 seconds of manual fast
idling, as longs as the weather was over 40
That was all we needed to hear. A few weeks later, our
trusty double-pumper was reworked, back
in our hands and bolted on the Beeper’s Victor intake.
Sure enough, it works! While the
pump shot duration isn’t long enough to
cover a mash-it-at-25-MPH-in-drive-andwait-
for-the-kickdown-to-first scenario, just
a small dose of driver intellect, applied as
manually downshifting (to at least second
gear) before mashing the throttle, is a simple
and effective workaround.
All in all, the Carb Shop’s double pumper
worked out extremely well.
Source: The Carburetor Shop, 1461 E. Philadelphia, Ontario, CA 91761; (909) 947-3575
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