➔HANDS ON
RAM
JAM
Kinsler supplied the 9-inch-long, 1^15 ⁄ 16 -inch-diameter, spun-aluminum ram tubes ($35.82 each). The adapter bases were fabricated by
Bay Path Vocational Technical High School in Charlton, Massachusetts. Aside from the induction and headers, the DOHC 4.6 is stock
(factory rated at 305 hp at 6,750 rpm and 320 lb-ft at 4,200 rpm).20 CAR CRAFT AUGUST 2019
Does Ram Tube
Length Transform
the Engine, or Is It
a Cherry On Top?
R
am tubes look cool. Whether
towering a foot over the hood of
a retro altered-wheelbase 1965
Hemi Coronet or tucked down tight
under the closed hood of a modern
Pro Touring Camaro with LS power, ram
tubes are mechanical jewelry. But what
do they actually do, and why are some
ram tubes so much longer than others?
Is it just style, or is there more to it?
To offer some insight, we took the
author’s eight-stack, EFI-equipped
Funny Fairmont and visited Dave Brady
and Greg Gemme’s Enhanced Street
Performance (ESP) in Sterling, Massa-
chusetts. There, we strapped the
machine to ESP’s Mustang all-wheelchassis dyno to explore the effect of
ram-tube length on horsepower and
torque at the tires.
Also known as velocity stacks, ram
tubes are most commonly found on
individual runner mechanical and elec-
tronic fuel-injection systems. It’s the
purest form of naturally aspirated
induction, as they’re free from the flow
obstructions (choke, venturi area,
booster legs, and so on) that haunt
carburetors. By manipulating the total
length of the ram tubes, we can take
advantage of resonant pressure waves
that exist within the intake tract of
every naturally aspirated (non-boosted)
reciprocating combustion engine.We don’t have enough space here to
fully explore ram tuning, but suffice to
say, with each intake stroke, a column
of fuel and air travels through the intake
tract at about 1,100 feet per second.
This column has significant mass and
momentum. When it hits the back of
the closed intake valve during the com-
pression stroke, it has stored energy.
Now imagine this column of energized
air bouncing around when the engine is
running at high speed. That’s a lot of
energy waiting to be harnessed.
By manipulating the length of the
intake tract (most easily done with rep-
licable ram tubes of differing length),
we can tailor how much of this storedBy Steve Magnante / Photos: Steve Magnante