Originally Posted by
27mtaylor
Mine has a Borla exhaust system on it, but I still need to give it a K&N filter. I have thought many times about the ignition system. So you noticed a big increase in power with the MSD and HyFire system? What are your opinions on the Throttle body spacers? Its a cheap upgrade, but I've heard mixed reviews.
The K&N kit made a noticeable difference in seat-of-your-pants torque and upper RPM HP.
The ign upgrade helped idle quality, torque, and cut down on spark-knock under loads. I think it helped with fuel mileage, but never actually did a before & after to see. I pulled a 16' flatbed with my '57 Chevy on it.
When I was racing, spacing the throttle plates from the manifold would create upper RPM horspower at the expense of low RPM torque and I was not willing to spend the $70 to try it on the Jeep. (that was with carbs, though)
I talked to a guy in Denver that did the TB spacers as part of an upgrade pkg. (with Airaid filter kit) and he said the results were minimal at best and that I probably would not notice any difference.
The Mallory was $99 from Jegs and the coil was $35. I put an 8.8mm wire set on at the same time. I use only Champion plugs in Chrysler products. They are the only cars I use them in. They don't fire worth a crap in anything else I've screwed them into, and nothing seems to work as well in a Mopar.
According to JP magazine an air filter kit, exhaust kit w/ header, oversize throttle body and Hypertech software program combined are worth 20 hp and 20 ft lb gain at the rear tires. That would put a stock 4.0 at roughly 150 hp and 200 ft lb torque.