the effects of Ram Air
you remember one thing from high school chemistry class, it
might just be that gasses, such as air, become denser when
cooled. When it comes to engines, cold air means more molecules
of oxygen available for combustion. This boils down to more
Supplying an engine with fresh cold air is a benefit most
auto makers have exploited since the '60s. Unfortunately the
better air quality usually comes at the expense of
air quantity, as the factory air cleaners are restrictive
and designed to minimize sound rather than maximize flow.
Most of us try to solve the quantity problem by installing
the "muscle car" standard, a 14-inch open element
air cleaner. Though it does breath well, it sucks in hot air
from the engine compartment.
The ideal situation is a ram-air setup, which not only provides
the engine with cold air, but also large quantities of pressurized
air. Air pressure at the front of a car can be as high as
3" of Hg at 80 mph. Directing this to the carb is essentially
a free, albeit very small, supercharger!
Until recently making an effective ram air induction for your
carbed engine meant either installing a big and conspicuous
scoop on the hood, or fabricating an sealed air-cleaner and
running ducts to the front of the car. In other words, it
wasn't a simple task, and the end result often didn't look
Fortunately a company called Air Inlet Systems has made installing
a ram air system on your carbed Ford a very simple project.
AIS makes the "Ram Air Box" a high-capacity, air
filter housing with twin snorkels. The hand-laid fiberglass
housing has been designed to optimize air flow and pressurization.
Flow comparisons between the stock 1985 Mustang HO dual-snorkel
(14"x3") air-cleaner and an AIS 14"x3"with
80 deg. snorkers, show an increase of over 350 cfm (Superflow
1020 pro-bench with pressure set at 10 inches of water.)
The beauty of the Ram Air Box, besides its exceptional flow,
is that is utilizes a standard 14" diameter base, lid,
and air filter. Depending on hood and engine accesory clearance
the box itself can be ordered in a 3", 4", or 5"
tall configurations, with either 80 or 110 degree separations
between the snorkels.
AIS claims most users see a 2 to 4 tenths improvement in ET,
and as much as 10% increase in power and long range fuel economy.
We decided to see if we could confirm these claims for ourselves.
Our 1967 Mustang had been running consistent 13.0 - 13.10
for the past five months, with seemingly no hope for a 12
second time slip. No matter what we tried we could not gain
that extra tenth. So needless to say, we weren't too convinced
that the Ram Air Box would do it. Fortunately we were proved
wrong! Very wrong! Quarter mile results confirmed over 2 tenths
improvement and a gain of 3 mph over our previous bests without
ram-air. To top it off, we noticed an increase of about 2
mpg on our 100 mile roundtrip drive to and from the racetrack.
track tested the Ram Air Box on Project '67. We made
no changes to the engine or car other than installing
the Ram Air Box. The 289 powered Mustang had run a previous
best of 13.03 @ 104. Just to show its no fluke, we made
six passes on the same day with the Ram Air Box, and
all six were in the 12's! The top three are listed here:
w/ air filter
w/o air filter
Ram Air Box
(Previous Best ET)
is absolutely no doubt that the design of the Ram Air Box
yields convincing results. This may in fact be the cheapest
horsepower you can buy for your carbed Ford! We were also
curious if the Ram Air Box worked better without an air
filter, but we actually lost a tenth and 1 mph without it.
We figure the air filter reduces turbulence in the box and
straightens the air flow to the carb. As mentioned before,
we used a cheap paper filter, but a good cotton gauze will
flow better. Who knows, we may still be able to squeeze
another tenth out of the 289!