In the realm of tinkering for more power, the pitfall is to be unable to quantify progress. It's easy to convince yourself that those muffler clamps added 20 horsepower. So to do this right we knew we'd have to evaluate each change, and that requires dyno or drag strip testing. We decided upon the chassis dyno at K&N Engineering (yes, the air filtration people), who have an extremely accurate and repeatable setup. The fact is, with a street driver on the strip, we can see our times change 3-4 tenths in the course of a day, and a like amount based on driving style. Sure, a true and consistent drag car is best evaluated on the strip, however, for testing on a street car, once strapped onto the Dynojet with its repeatability to within a horsepower, there's no place to hide from the truth.
It's easy to hit the dyno with an engine that runs like a pig, timing a mile out, worn plugs, burnt wires and all, then fix what's obviously broken and bask in the glory of big power gains. Now, we're not goofy when it comes to turning a wrench. You won't be able to twist off the distributor and change the plugs to gain forty horsepower. We wouldn't be driving this car if that hadn't already been done. This Charger is already fairly well tuned for what it is. To ensure that our 440 would deliver its best before making the trip to K&N, the plugs were swapped for a fresh set of Accel units, and we cut a new set of Accel wires. The timing was correctly set to 36 degrees total advance (mechanical advance fully in; vacuum advance disconnected), and a new paper air filter installed.
On The DynoWith the car strapped to the K&N chassis dyno, we worked to establish a baseline. First we made a few runs with our stock package to establish the optimal ignition timing. As expected, our best-guess setting of 36 degrees total proved to be optimal, and we would retain this setting for the remainder of our testing. Since we had a B&M Holeshot torque converter, testing below 3000-3200 rpm was not possible because the torque converter would flash to at least this rpm off the roll when stabbing the throttle on the dyno. Looking at the dyno readouts it was clear that the stock engine combo was producing peak torque below our minimum recordable rpm level, making it impossible to obtain a peak torque reading in testing. Peak torque was at an rpm low enough to be off the bottom of our chart, therefore, we will report only the horsepower numbers. If the horsepower is up at any given rpm, obviously, so is the torque at that rpm.
For the purposes of getting the most realistic numbers, each test shown is the most representative of a minimum of three pulls. The highest and lowest pulls are thrown out, and if there were any anomalies, the tests were run again. Our baseline run is recorded in Test 1. Peak horsepower was 225.1 at 5000 rpm-a typical rear wheel number for a stock 440. With the stock 440 Magnum valve springs of unknown mileage, the beginning of valve float was clearly audible at 5200 rpm, putting a definite ceiling on our useable rpm.
Air FiltrationOur first test was with the stock dual snorkel air cleaner and a replacement paper filter. Replacing the air filter involves spinning one wing nut, so this was to be our first mod. We decided to change the whole dual snorkel filter box and go to a 360-degree open element air cleaner-the typical 14-inch chrome air cleaner with a K&N filter. The outcome is recorded in Test 2. It shows that the dual snorkel is not enough even with a stock 440, with a maximum gain in our test of over 10hp at the rear wheels and more power throughout the rev range.