Terminator Exhaust for Project 11.99
up with an exhaust system for a strip car is a bit more challenging
that for a street car. On a car that is predominantly used
for the street, your concerns may be, in this order, sound
quality, power, ease of fitment, and perhaps durability. Let's
face it, most people who get an aftermarket exhaust do so
for the sound. They want a mean, aggressive sounding tone
on the outside, but not too invasive and "drony"
inside the car.
considering an exhaust for a strip car, the priorities change.
Sound is still a major factor, but in a different way. This
time it's the track officials that are imposing the sound
requirements. Many tracks have a rule, imposed by surrounding
communities, that cars must not exceed 95db, measured at 3500
rpm from 50 feet from the car. Also many classes of bracket
racing require the car to be "fully muffled." However
rarely is the sound actually ever measured. In fact we have
never seen a db meter used by an official at the track. Rather
the officials simply use their discretion and authority to
determine if a car is too loud. This typically means that
all cars must have mufflers, even if the car can meet the
95db requirement through open headers. Most officials simply
peek under the car, and if it has mufflers, it's okay to run,
regardless of how loud it is. In fact we usually see open-bodied
dragsters with huge 5" mufflers, which are clearly louder
than 95db, being given the go-ahead nod. Yet when we tried
to run Project 11.99 through open headers and 18" extensions,
we were told to get mufflers or go home.
So we decided that it was time to get an exhaust system under
the '67. When it comes to putting an exhaust system on a strip
car, first and foremost you want an exhaust system that does
not rob horsepower, and thus hurt ET's. While a few cars may
actually see a gain with a well designed exhaust system,
the fact is many, if not most, will run better numbers with
open headers. With the previous 289 engine, we ran a consistent
2 tenths and 2 mph faster through the headers than compared
to a 2.25" exhaust. While it is easy to say that an exhaust
system is restrictive, that is not the sole factor contributing
to the loss of power. Exhaust systems are added weight, as
much as 60 pounds. They also change the air/fuel ratio and
scavenging characteristics of the cylinders. There is also
the debate over backpressure, and whether engines benefit
from slight backpressure. Most experiments have shown that
backpressure typically increases low-mid range torque, at
the expense of power at the top end. On a street car that
operates between idle and 4000, 90% of the time, back pressure
is desired as it puts more power in the usable range. On a
strip car, operating at no less than 4000 rpm, you'd rather
have the top end power.
Our goal for Project 11.99 was to put together an exhaust
system that lost no more than one-tenth versus running open
headers. We decided to go with a three inch system, that ends
at the mufflers, just shy of the axle housing, as opposed
to having tail pipes bent over the axle and under the rear
bumper. The less bends in the exhaust system means less restrictions
and reduced back pressure. Because the car is driven 150 or
so miles round-trip to the track, we also needed a system
that was somewhat quiet. In reality, if sound was not a concern,
we could have simply bolted on two "bullet" style
mufflers directly behind the collectors, and had virtually
zero restriction. However we've done this before, and it is
LOUD. With the drone and resonation under the floorboard this
turns out to be louder than open headers.
contacted Flowtech (Holley) and told them about our engine
combo, and they suggested their new X-Terminator pipe and
Terminator mufflers. We decided on 3" because it is slightly
less restrictive than a 2.5", plus if we go to a larger
displacement engine in the future, it will still be up to
the task. The 3" pipe will be louder than a 2.5",
and it's more difficult for the exhaust shop to work with.
For a street car, 2.5" would be preferred. The Terminator
mufflers are their highest flowing mufflers, and are claimed
to outflow the "F" brand. Besides, we didn't want
our car sounding like everyone else's! It is a steel design,
fully welded, and utilizes chambers and perforated tubes for
sound control, rather than glass packing which tends to burnout.
They are not light, nor are they compact. At 15 lbs a piece
and 5"x11"x15", they are on the bulky side. You'll
want to make sure they fit under the car first!
took our mufflers and crossover to Mel and Sons Mufflers of
San Pablo, CA. These guys are artists when it comes to fabricating
custom exhausts, and they have a great reputation around here.
Choosing a competent exhaust shop is just as important as
buying the right exhaust components. We've had shoddy exhaust
systems put together in the past, and they suck. Poorly bent
pipes, bad welds, asymmetrical pipes, etc... it not only looks
bad, but robs power and eventually falls apart. It's worth
driving a bit farther and paying a little more to have it
What we ended up with was an incredible looking and sounding
system. The sound of the X-Terminator pipe is very unique;
at high rpms it emits a higher pitched note, very similar
to something you'd hear at Daytona. To be honest, the system
is louder than we thought it would be at idle, but the X tends
to quiet out the note at part and wide open throttle. F/M
about the track results here!
Part Number: 50130
down the 3" barrel of the Terminator
muffler above, and X-Terminator Pipe below.
A Division of Holley Performance Products
It's long been known that connecting the two sides of
a dual exhaust system, shortly after the headers, increases
power and reduces sound. However in a traditional "H"
pipe, only sound and pressure waves cross through the
connection. Gasses take the route of lowest pressure,
which is straight out the pipe, rather than making a 90
degree turn in to the H.
Indy and Nascar teams have been using "X" type
crossovers for quite some time. In an "X" pipe
the gasses from both cylinder banks actually pass through
a common area. This not only provides the benefits of
some sound wave cancellation, but also increases the scavenging
effect, helping draw out spent charge from the combustion
So how much of an increase does an X gain over an H? It's
hard to say, especially considering that every combination
will yield varying gains. In theory an X will work better
as rpms go up. Considering the Flowtech X-Terminator pieces
are priced under $50; you're much better off getting that,
rather than having a shop fab up a crude 'H' piece.