After putting on heads and cam on my car with Hooker cat-back, the car was really loud and raspy. I just added a hi-flow 3" cat on Saturday, and it's definitely a lot more liveable now. It sounds really good. I would guess it's a bit louder than the car was without the heads, cam and headers. I was just tired of the noise and not wanting to rev the car for fear of getting pulled over.

I live in California, so removing a cat is a bigtime fine here. They had a big sign on the wall at the muffler place saying that removing or tampering with the cat is subject to a fine of $2,500.

The strangest thing was that the car feels stronger on the low end with the cat on there. I guess adding a bit of backpressure helps the torque. It still feels the same on the top end, though.

My only concern is how long the cat is going to live. With the cam, it's going to run rich at low RPM. I don't know that there's much that can be done to get it to the right AFR at idle. I am getting a bit of a sulfur/rotten egg smell at idle. Anyone else have this? Is this going to cause the converter to fail?

BRAD

 

I had a new high flow cat clog up after 9 months (heads, cam, blower). I ended up hollowing out the cat. I had the cat flanged and have a new cat that I use at smog time. I'd rather not do this but I'm not going to replace the cat every 9 months. The hollowed cat "looks the part" under a visual inspection.