Performance concerns

From: jim miller (
Date: Sat Jun 13 1998 - 19:54:08 EDT

Jim Miller writes;
I am still not satisfied with the way my new truck runs. It is a 98 reg cab swb 5.2L auto, 3.92 sg Mopar headers but stock exhaust behind it with 400 miles on it. Today I put the Mopar FABM on it and tried a couple of 0-60 runs. I was quite
dissapointed. The truck actually seems to loose power with the FABM on it compaired to the factory air cleaner and filter with a fresh air duct opening beside the radiator in the grille area. Here are the results.
With FABM 0-60 first try 9.98 seconds no power braking. second try 10.03 seconds.
With stock air cleaner and filter with fresh air duct 7.99 seconds and 8.01 seconds.
Outside air temp 102 degrees and 39% humidity and 600 feet above sea level elevation.
There is minimal wheel spin with stock air cleaner and no wheel spin with FABM.
Also with fabm the engine almost quits pulling totally about 4800 rpm, with stock filter it quits about 5k.
I seem to loose a lot of torque with the open filter and gain no top end either.
Could my problem be putting headers on with the stock exhaust is a very bad combination?
I am waiting for a catback system I ordered but the dealer installed the headers when I bought the truck. Am I expecting too much from a 318? My 89 Shelby Dak ran better than this truck does.
That truck would smoke the tires 50 feet but had no high rpm performance. Of course I know it was only 175 hp but was a little lighter than the 98. I still believe the 98 should have more hp per pound. where am I going wrong. Can I put a K&N
filter in the stock box and help myself. The underhood temp is just too hot in Texas summer for underhood air input.
BTW I am running 87 octain gas, no ping at all and it cost 90.9. 93 octain is 100.9 here.
Jim Miller

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