The stock 4.0L exhaust manifold would not place well in an airflow test. On the other hand, aftermarket headers are tubular and designed for efficient air flow.
Take your pick. There are several vendors providing quality products in a variety of price ranges. Each has their advocates. Some advocate for ceramic coating. All agree on tubular construction.
I did a review of the various products available and selected the JBA Performance Exhaust header as a reasonable price option. JBA has long been respected for their aftermarket headers for improved performance with the Mustang. They now carry that reputation to the Jeep 2.5 and 4.0L engine market.
Installation is a matter of removing a lot of nuts, bolts, screws, pieces, and parts before you can access the bolts holding the header in place. Once the header is removed, the head mating surface needs good cleaning to remove the old gasket material and carbon deposits.
A new head flange gasket is provided. Use care when installing the header so as not to damage the gasket. With the header in place, the remaining pieces and parts can be reinstalled. The final connection is to the exhaust pipe. The JBA header does have a direct fit to the exhaust pipe without need of a collector gasket. New collector bolts, nuts and lock washers are provided.
The complete job requires attention to detail and no special tools. However, as the fuel line does need to be disconnected, allow time for the fuel pressure to bleed. And, it is easier to work on a cold engine.
Okay, does it really make a difference? If I were to brag about increased performance, I would have engine dyno tests to back up the claims. I don’t; but, I did note a significant performance improvement.
On a recent trip through the mud hills of Ocotillo Wells SVRA, I was pleased that I now have better throttle control at off-idle.
Overall, performance is a subjective determination based on intake, exhaust, and overall gearing. Having better off-idle throttle is a performance improvement and keeping the engine running smooth is important.
Work was done by:
Roger Daniel's Alignment & Brake
8517 Ablette Road, Shop F
Santee, CA 92071
BAR # ARD214109