2001 Ford F150 - Project Sinatra Part III: A Matter Of Breathing

All of this rusty garbage would soon be a thing of the past.

Some broken catalytic converter chunks were found in the original aftermarket exhaust's muffler, which accounted for the rattling noises we heard. This miniature MagnaFlow muffler is actually a resonator from one of its Mustang kits. We pulled the entire prior-aftermarket system and straight-piped the exhaust with this small muffler and it was surprisingly quiet until the throttle was mashed, which was a testament to MagnaFlow's design.

To remove the OE Y-pipe, the transmission crossmember needed to be removed, as well. A jack was used to support the transmission while the crossmember got the ol' heave-ho.

It's hard to even imagine that rusted hulk next to the MagnaFlow catalytic Y-pipe could even have worked properly anymore. The chunks we found in the exhaust and a flow test confirmed that this system was garbage. Taking no chances, MagnaFlow installed all brand-new O2 sensors, instead of attempting to use the stock ones first.

The all-stainless catalytic system should now last longer than we'll be able to drive the SuperCrew. Every weld was professional in appearance and the O2 bungs were exactly in place as they are on the factory part, which made this system a smog-legal replacement.

With the fresh Y-pipe and catalytic converters in place, and the transmission crossmember reinstalled, our project looked to be headed in the right direction. The all-new hardware was used because of the aforementioned rust problem.

Moving on, the MagnaFlow after-cat exhaust was next in line. With the brand-new Y-pipe installed already, the after-cat went on faster than we could photograph. There were no more problems from here on out!

Our technician fed the rear portion of the tailpipe over the axle and hooked it to the muffler's outlet, But then we ran into another problem. I guess we had spoken too soon.

The rearmost exhaust hanger was missing from our truck. No dealers near us had one, so the proper solution was to just weld a MagnaFlow one onto the frame and call it a day.

Finally completed with all of the intake and exhaust modifications, we headed to the rollers of the dyno to see if we had gotten somewhere.

Our anemic 4.6L turned out an unimpressive 237.34 hp and 268.63 lb-ft of torque with the blower and after-cat exhaust filled with broken catalytic-converter internals. After the intake and exhaust modifications, the truck scraped together 251.94 hp and 273.84 lb-ft of torque at the wheels. The computer has never had any adjustments or programming, the consequence of that was timing that bounced all over the place as the stock computer tried to make changes it couldn't make. Our A\F ratios were all wrong to boot, and that accounted for the minimal 14.6 hp and 5.21 lb-ft of torque gains.