Installing A Performance Exhaust For A Ford Mustang - Exhausting The Possibilities

The headers are in place on the engine. It's up to Dan to create collector cones because we lost the originals. Although the Hedman catalog calls for a C4 transmission only, it's nice to see the headers also clear an AOD without a problem.

With all of the needed components fabricated, Dan proceeds to weld the whole system. Two complete exhaust changes in two days have kept our guy pretty busy, and other cars are beginning to pile up.

We like these results better. The headers gained us 10.26 in horsepower and an even better 14.69 lb-ft of torque. But the underlying lesson to all of our dyno work on a basically stock Mustang is this: Don't expect big horsepower and torque gains unless you're willing to enlarge the rest of the exhaust sys-tem along with whatever goes onto the side of the cylinder head. In our estimation, adding a 2-1/2-inch exhaust system with some free-flowing mufflers would make either the K-manifolds or the headers do much better. We would expect the K-code castings to be worth 10-12 hp, while the headers in front of a bigger system should be worth 25-30 hp or more. We've also tested long-tube headers on popular stroker engines in the past, and have seen even higher gains on these healthy, deep-breathing engines.

The last connection is mechanical, with the lower flanges being secured to the new pipe with cap screws, lock washers, and nuts. Check out the weld quality on that header cone, and it's easy to see the mark of experience. Now it's off to the rollers at Superior one more time.