Our subject for this experiment, a Rat-powered '69 Z/28, started out with a wasted exhaust system.
The mufflers had touched down at least once, the packing long gone. The tailpipes had also been hacked off, givng the exhaust note a gargling, raspy tone. We responded by installing one of MagnaFlow's new American Muscle crossmember-back systems. The exhaust note grew sharper and cleaner, taking on a growling sense of urgency the discarded pipes lacked. The veteran Z sounded leaner and meaner--and leaner was just what this ride needed.
Looking to reduce backpressure without sacrificing exhaust gas velocity, MagnaFlow's Richard Waitas picked a 2.5-inch setup for this mild-396-powered F-body. So just how much was flow improved? According to readings during our pre-install pull on MagnaFlow's Dynojet chassis dyno, this fat-block was running rich, registering an air/fuel ratio of 11.5:1. With the new tubes in place, our mixture was almost a half point leaner, checking in at 11.1:1. Accordingly, we picked up 13.5 hp and 14 lb-ft--with more to be had. "This car could stand to lean out to 12.0-12.5," Waitas told us. "Typically a solid 1-point change would be good for another 5-10 rear-wheel horsepower in a big-block Chevy."
The whole job only took half a day, and MagnaFlow recommends that a professional install its products, but a layman who can handle a bit of welding can do the job. Either way, the payoff-- both to the ears and at the pedal--is well worth the effort.
Click on the links below to see and hear the before and after installation of the Magnaflow American Thunder exhaust system
Quicktime Movie Before Windows Movie Before
Quicktime Movie After Windows Movie After