Automotive Holley Carburetor Dyno Testing -
horsepower gains with a
Superior Automotive Holley
carburetor hop-up kit
Automotive Gets More Power From A Brand-New Holley
known for a long time that Superior Automotive in
Anaheim, California, is a gold mine for Ford high-performance
expertise. The folks at Superior Automotive work
on all kinds of American muscle, but there's always
something interesting going on from a Ford-performance
perspective whenever we pay them a visit. From garden-variety
Mustangs to the more esoteric visitors-such as a
'48 Mercury convertible with a 460 conversion-on
any given day, a visit to Superior always makes
us feel like kids in a hobby shop.
issues past, we visited the in-house carb shop and
came away with extra horsepower. With more than
40 years of experience, Don Spaccarotella is the
apostle of horsepower at the carb shop. He's especially
adroit at resurrecting basket-case Holley four-barrel
carbs. This time, we thought we'd throw him a curveball
and see if he could get anything out of a brand-new
This is our new 650-cfm Holley double-pumper
carb. With the car strapped onto the rollers,
the idle is adjusted prior to the first pull.
Superior Automotive's Don Spaccarotella runs
the '69 Mustang through the gears, settling
in Fourth before the throttle is nailed, while
carefully watching both the rpm and the air/fuel
ratio. Several pulls were taken to ensure
repeatability and to make sure there were
no major problems with our project car.
new Holley four-barrel is a 650-cfm unit sitting
atop a fresh 351 Windsor. The double-pumper carb
has a mechanical secondary, and the only alteration
is that the choke has been wired open. The carb
has about 2,000 miles on it, and the engine runs
like gangbusters. Holley knows what it's doing when
it comes to building carburetors, and a new Holley
four-barrel will usually run fine right out of the
box provided it's appropriately sized to the engine.
Such is the case with our carburetor.
we approached Superior with the idea of throwing
Spaccarotella the new carb curveball, the company
agreed to the story. Its employees have confidence
in their man and know he will deliver. We wanted
new baseline figures before the carburetor was modified
and then a second session on the Dynojet to measure
the result. To eliminate as many variables as possible,
our test used the same Dynojet on the same day,
with the same operator. Much of what Spaccarotella
does is confidential, but if you send Superior your
carb, the company can modify it, new or used.
us to the Dynojet at Superior to see if Spaccarotella
can squeak a few more ponies out of a new carb.
Normally, for a performance rebuild, the carb
is completely disassembled and soaked in solvent
for cleaning. Because the carburetor is new,
Spaccarotella says he won't remove it from
the engine. The central body of the carb remains
in place, while various components are removed
and replaced. Here, the rear float bowl is
drained into a receptacle designed specifically
for this purpose.
With the float bowl empty, disassembly begins.
Here, the four float-bowl retaining bolts
Next, the float bowl and the metering block
sandwiched between the float bowl and main
body are removed. The float levels are fine;
Spaccarotella is interested in the metering