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Bad Cat! Good FYI


Well-known member
Jul 3, 2001
Auburndale, Florida
1969 Killer Shark
Just some quick FYI. I am new here and I am sure this has been covered 1,0000000 times.

Anyway, my wife has a 90 six speed coupe. We bought it back in 98 from Sunshine Corvettes in Central Florida. (very nice people)

My wife drives the car 99.9% of the time. I noticed that it did not have a whole lot of pep over 4,000 RPM. However, it is typical for the T.P.I. to whimp out a little on the upper RPM band. She complained to me that it was not as fast as her 89 six speed and kept urging me to do something. Okay, I ignored the situation as long as possible.

She recently decided to auto cross the car. It became glaringly clear to me that we had a problem. We installed a pair of Flowmaster mufflers and it barely made any more noise and did not seem to gain any performance.

Long story short, I slipped underneath and found the center cat to not only be bad, but it was coming apart and working its way through the rear Y pipe. At least one of the two Pre-cats was broken up internally. Her first SOLO II performance, the car really struggled and the engine was getting too hot too fast. In fact, it never overheated, but had a habit of getting too hot for comfort in the past.

Now the exhaust system has a clean bill of health---and whoa Momma--the fun is back. It revs smooth and strong, the flow master rumbles and she is able to push it to the limit in SOLO II.

So, if your Vette is a little sluggish, makes any strange rattle underneath, and does not have that zoom zoom, check out the CAT system. The middle one is easy to check. The pre-cats are not visible inside to the naked eye and would require a temp drop test, rattle test, or just replacement if you have a lot of miles on the car.

I know the feeling. Taking off the cat unleashed my car. The sound is awesome too! If you dont have emissions check. Go for it. :upthumbs

I ran into the exact same thing on my '85. I replaced the cat with a test pipe and ran with it for about 6 months (in combination with my 2 stage racing Flowmasters and headers. Needless to say, the sound was deafening. I removed the test pipe and replaced it with a hi-flow Random technologies cat and I kept the performance and lost the noise.

It mad a huge difference running the test pipe, but the headaches were not fun. The Randon Tech cats did not take away very much performance. I even removed the headers because of the noise, and replaced it with my GTS Coupe.:s :Twist :gap

I am happy with both cars now.


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