Exhaust and Catalytic Converter


Replacing the vintage 1975 catalytic converter on a Corvette is a good way to improve performance by allowing your car to breathe better. Pictured here is a PFP (Products for Power) catalytic converter. Cost: $149.00.
This is a view of the inside of the PFP cat through one of the inlets. The inner structure looks like a fine mesh. The glow at the top of the picture is light showing through the cat from the opposite end.
The rear y-pipe is made of aluminized steel. Cost: $129.00
I found that putting the Vette on ramps gives plenty of room to do the work.
Removing the exhaust was quite simple. I had to remove the 4 bolts connecting the front of the cat to the front y-pipe, two bolts that held a bracket to the rear of the cat and the muffler mounts. The whole rear part of the exhaust dropped easily after removing a total of 8 bolts.
Once the exhaust was off, I found that one of the mufflers was rusted through in a place not easily seen with the exhaust on the car. The rear y-pipes metal was so fragile that it bent easily with my bare hands. Not a surprise considering the age of the car.
The old cat is big and heavy. Shaking it, I could hear rust and other junk banging around inside; a sure indicator that it needed replaced. You can see by looking at it that the car bottomed out a few times.
With new mufflers added (cost: $119 pair), I loosely assembled the exhaust before I installed it. Since I was working alone, I used concrete blocks and pieces of 2 x 4 to prop everything up to allow me to align the exhaust properly on the car.
Fitting an exhaust is not an easy task. It takes time and a lot of patience. One thing I would suggest having on hand is an assembly manual. An assembly manual graphically depicts the minimum tolerances allowed between the exhaust parts and the body parts. These distances are critical because they prevent banging, rattles, and melting fiberglass.

My verdict? A definite improvement. The car sounds better and performs better. I found during a brief test drive there is much more apparent power around 4000 RPM. After running a full tank of gas, the fuel economy improved by 1.5 MPG. An upgrade must.