At the O'Reilly Auto Parts Fall Street Machine Nationals in Springfield, Illinois, last year we spotted a dyno sheet on the windshield of Steve Engberg's '69 Mustang Mach 1. What demanded closer inspection was the sheet's 595 rear-wheel-horsepower (rwhp) number from a car that appeared to be more of a resto than a runner.
Looks can be deceiving. That...
Looks can be deceiving. That air cleaner hides more than just a 463ci stroker Ford.
That led to a short piece in our Feb. '05 issue ("Make Mine Mach"), but what was appealing about Steve's 463ci screamer was the Nitrous Oxide Systems (NOS) Top Shot kit he had installed inside the repro Shaker hood air cleaner. Steve explained that he would have used a typical under-carb plate system, but the added height would not allow the hood to close over the Shaker scoop. Instead, he chose the Top Shot system, which worked extremely well. His normally aspirated power numbers measured 472 rwhp, while the nitrous pass revealed an astonishing 573 rwhp--almost a 100hp surge in power. Later, he tested the car again with a better tune-up on a much cooler day and squeezed out 592 rwhp on the bottle. We decided to learn more about this Top Shot system.
The secret is the Nitrous...
The secret is the Nitrous Oxide Systems (NOS) Top Shot 150hp system that owner Steve Engberg has hidden inside the air cleaner. One squeeze and the horsepower jumps to almost 600 at the rear wheels.
The idea behind the Top Shot is to make it quick and easy to install a nitrous system on a carbureted engine without removing the carburetor. Key components in the system are four nitrous and fuel discharge nozzles fitted into a round fixture designed to slip over the air-cleaner stud. The feed lines for fuel and nitrous are designed to easily route through the base of the air cleaner and could then be snaked through an innocuous rubber hose if total stealth is your goal.
What makes this kit even more fun is that the added power is adjustable between 75 and 150 hp using the same jets found in the more upscale NOS systems. The kit comes with jets for 100 to 150 hp. The kit is limited not just by the jet sizes, but also by the orifice sizes on the discharge nozzle. Replacement discharge nozzles are also available, so if you already have a plate system, you could buy the nozzle alone, add a few fittings and have a Top Shot system for a little extra fun.
Steve says the key to making this system work is to ensure the spray from the nitrous is not aimed directly at the carburetor booster. If the nitrous sprays into the booster, this will affect the booster signal and fool the carb into running full rich, which will kill power. Steve checked this by triggering the fuel side with an electric pump and aiming the fuel shot away from the carb boosters.
Combine an honest 125 to 150 hp with an incredibly easy installation and you have all the ingredients for maximum fun at the touch of a button.
 This is the Top Shot kit from...  This is the Top Shot kit from NOS. The biggest hassle is mounting the nitrous tank. The rest of the installation is easy. |  The key to this kit is the...  The key to this kit is the Top Shot module straddling the air-cleaner stud. NOS recommends carefully positioning the module by using the aluminum extension tube between the carb and the module so it avoids shooting nitrous at the carb boosters. |  The module is drilled with...  The module is drilled with four outlets into its base, one each for nitrous and fuel for the primary and secondary sides of the carburetor. |
 The Top Shot system allows...  The Top Shot system allows easy jetting changes by merely swapping jets fitted to the Top Shot module. |  The solenoids in the Top Shot...  The solenoids in the Top Shot system are small but still capable of flowing enough nitrous and fuel to make 150 hp. The module is the limiter in the system, preventing you from adding larger solenoids. |  A good fuel pump and delivery...  A good fuel pump and delivery system is essential for this kit to work. You need a minimum of 4.5 to 5 psi of fuel pressure when the nitrous system is employed under load so the system does not run lean. |
This is what the Top Shot was installed in. We told you this thing looked like a pampered resto. This is one little Mustang that definately moves.