CaminoSS

As some of you might recall my 90 took a little love tap on the backend a couple weeks ago and my cat back is toast. I am still fighting with the insurance company to get my money, but I am not sweating that. I will get my money adventually.

But from the love tap and the exhaust getting shoved in, the main cat broke up inside and clogged up on me. I did my homework on this sight as well as some of the vendor's sights and came up with the most cost effective solution I could.

Since the L98's have 2 pre-cats and one large main cat, there is restriction with the original equipment. My pre-cats had been replaced right before I purchased the car in the spring. The main cat was still the original and even if the accident had not happened, it probably would have failed soon anyway. To repair it properly would have meant replacing the pre-cats and the main cat, since the pre-cats normally help contribute to the failure of the main cat. That would have been pretty pricey to say the least.

What I choose to do based on the collective knowledge from this sight and the vendors was to eliminate the pre-cats and replace the main cat. Someone posted on here that you would pick up about 40 horse just from getting rid of the restrictive old style cats. As to the validity of that statement, I have not seen any hard evidence. But by reducing the restriction, I could do nothing but pick up power.

I just drove the car home and what a difference!! Yes, she is louder, but louder is not bad in my case. Much more aggressive rumble out of the Flowmasters. And the car pulls so much harder!!!!! I do not know how many horses were freed up from the pre-cats gone or from the less restrictive new cat over the old cat clogging over the years, but what a difference.

Some on here will argue that the pre-cats extend the life of the main cat, and that I will not argue. But the less restriction definetly makes a difference. And if I lose a little time on the cat, but pick up power and gas milage, then that is a fair trade off.

I just wanted to share this with you all.

86PACER

Nice.

'86 and up cars got the two pre-cats on the front y pipe.

I eliminated mine with a hooker front y pipe and run a random tech high flow cat along with long tube headers.

65Z01

That could be just a tad hight... ...I would say 15-20chp gain plus another 15-20chp if you install FL headers.

Indeed our stock exhaust is very restrictive; I would say a great deal of the gain for the LT1 is from the much cleaner exhaust setup.

j-wireman

I have a '90 L-98 with the OE cats.
What are the symptoms of deteriorated cats?
How can I test them to see if they are getting clogged?
What effect does it have on your emissions test by eliminating the pre-cats and installing a high-flow main cat?
Is the A.I.R. pump and tube to the cat still required?

Thanks for any info.

jonecap

I had a '90 that went from 14.20's to 13.30's in the 1/4 mile and picked up 5 mph just by doing the same thing you just did. Mine were obviously clogged, but it's amazing what a difference it can make.

65Z01

One symptom of clogged cats would be loss of top end power.

For max benefit, install a 2 1/2" mandrel bent front Y w/o pre-cats. If your are near Trenton, NJ I strongly suggest you have Mufflex custom build you a good front Y.

If you eliminate the pre-cats and install a modern 3-stage main cat you will easily pass emissions. My Vette, with this setup, easily passes the OH E-Check dyno sniffer.

You will still need the AIR pump to feed the main cat.

Puna

When you eliminated the pre-cats did you use an after market pipe kit and are you still using the o2 sensors ?

cv67

You can have your muffler guy drill a small hole, tap it and install a gauge to measure backpressure..IMO if the cats have more than 80k on them throw them out.