With the new 5.7L Hemi engine on the horizon packing 345 hp and 365 lb-ft, the original 8-year-old 360ci Chrysler small-block is looking a little lacking with 245 hp and 335 lb-ft. Don't get us wrong, these are great truck engines that make power low in the rpm range where you can feel and use it. It's just that we know our readers are never satisfied with the power they have. But we also realize that many of you are afraid to tear into an engine that is still covered by a factory warranty. So with both these things in mind we set out to see if real power gains could be squeezed out of a 360 V-8 by bolting stuff on and plugging stuff in without breaking any smog laws or removing the engine's valve covers. Here's what we found out.
Open Element Air Cleaner
With the new throttle body in place, Turbo City installed its dual-inlet air tubes with twin 5x5-inch K&N air filters. We like the way this setup looks and sounds at wide-open-throttle, but we don't really dig the fact that the intake now draws heated air from the engine compartment. Turbo City recognized our concerns and explained that even though the hot air entering the engine is not as dense as what the factory cold-air intake provided, the added volume of air now available to the engine would more than make up the difference. We suppose it might, but Turbo City agrees that more performance gains are likely if you added ductwork in the engine bay to direct cooler air from the grille to the new filters.
Throttle Body Modifications
Our 360's first stop was Turbo City in Anaheim, California, to have its throttle body bored and blended to flow more air. You can see the difference for yourself when you compare the stock unit on the left with the reworked piece on the right. If you were air, which one would you rather flow through? Both throttle bores were increased to just over 2 inches in diameter, the shrouding around each bore has been shaved off, and the throttle shaft was milled down to improve airflow into the engine. The best part is the modified piece bolted in place just like the stocker, but for our tests we used a 3/8-inch throttle-body spacer for $49.25.
Price: $229 plus a $200 core charge
Tying It All Together
To help the factory computer compensate for the increased airflow on our 360, Turbo City developed a manifold absolute pressure (MAP) adjuster. This module plugs in series between the Dodge's MAP sensor and the engine's computer to alter the MAP output voltage in order to make the engine run richer. To install it you must splice the supplied weather-pack connectors into the factory wiring harness, and connect the extra white wire to a 12-volt positive source that is energized with the ignition key in the "On" position. Mount the MAP adjuster so that you can reach the test port and POT screw. Turbo City zip-tied ours to the throttle body.
Feeding More Fuel
The face of the MAP adjuster has a test port and POT screw that allows you to effectively enrich or lean the fuel mixture in the engine across its entire operating range. Using a voltmeter, Turbo City read the baseline voltage the MAP sensor put out with the key in the "On" position, and then plugged in its MAP adjuster and added 0.2 volts to the baseline MAP voltage. Don't try to make adjustments without a voltmeter, as a small turn of the POT can make a huge difference in fuel supply. Performance and economy can suffer if not adjusted properly. You can experiment with various settings to suit your engine's needs, and even bypass the system completely by plugging the two connectors into each other.