24yrold&86conv

Hey guys. So I have a 1991 Corvette that's pretty modded and the Random Technology Catalytic Converter that has been in it since 1996 has kicked the bucket. At this point I was wondering if I should put another Random Technology Hi Flow Cat in that costs $350 so it's modded the same as when I bought it a couple years ago or if I should just eliminate it since I no longer have inspections in the New Jersey area since I will be getting classic plates cause it turns 25yrs old. The pre cats are already gone from when I got it with the below mods:

Cold Air Induction with K & N Air Filter

TPIS 52mm Throttle Body

TPIS Mini Ram Intake Manifold

TPIS ZZ9 Full Roller Cam and 1.5/1.6 Full Roller Rockers

New Bosch Flow Matched Fuel Injectors

New O2 Sensor

New Fuel Pump

New Fuel Filter

New Die Hard Battery

TPIS Headers

TPIS 3” Cat Back Exhaust

Random Technology High Flow Catalytic Converter

3” Flowmaster Mufflers

MSD 6AL Ignition

New Taylor Spark Plug Wires

DUI High Performance Distributor

Custom Burned TPIS EPROM (that is dialed in to absolute perfection)

Smog Pump Eliminator

antfarmer2

by by kitty.

dizwiz24

Hollow it out

24yrold&86conv

I was thinking of just KISS (Keep it simple stupid) eliminating it and putting just a pipe there lol. I wouldn't lose power or gain any, just save $350 and not worrying about the new cat breaking in the future...

John A. Marker

Even with the words HI FLOW.....they are still restrictive. Just try looking through a cat.....
If you hollow out or replace with a straight thru pipe...you WILL GAIN some HP.

24yrold&86conv

It will still be restricted by the weakest link cfm unit, which I think will be at the mufflers with this setup. What do you all think?

softwarejanitor

I don't think that's exactly how it works. To test this hypothesis try breathing through a tube that is 3/8" diameter and 6" long... now try one that is 2" diameter all but one 1" long section section that is 3/8". The one that is fat with just a small restricted section will flow better than the one that is skinny the whole way...

So eliminating one restriction will show some improvement even if ther are other restrictions. But in order to optimise it of course you need to remove every restriction possible.

24yrold&86conv

So I'll take that as another vote to delete the cat...

John A. Marker

The flows will not restrict you at all.

On my 85 when I started to mod the car. I put March underdrive pulleys on it and removed the single cat (in the center of the exhaust system) and replaced that with a straight thru pipe for 1/4 mile track racing. I took it to the track. Shocked myself. The car was turning 14.1 before these two modifications.......13.6 after. I don't think the underdrive pulleys helped that much, but there was no way to tell since I had not made the pulley mode....tacked it and then the cat mod with track time. BTW....the cat was a new HI FLOW Magnaflow cat.

24yrold&86conv

This car already has the under-drive pulleys from March Performance, part of the smog pump elimination kit. So what's your vote, replace with another hi flow like it was or put a pipe there to eliminate the only cat on the car?

patriotpa

gut it, run a pipe through it so it LOOKS installed. All they do is trade one waste gas for another, more harmful gas.

24yrold&86conv

I don't get inspected with Classic Plates, so I'll just run a new pipe without gutting.

WVZR-1

I don't know why if you're changing you wouldn't just do a "true dual" exhaust and be done with it.

antfarmer2

aklim

I'll bite. How much will you gain? If I were racing professionally and my next endorsement check was riding on the win today, that cat will have been long gone. OTOH, for a street car, it will make it noisy as all hell. So once again, what is the gain that would justify that racket?

aklim

I would say it is much easier to do a cat replacement than a true dual with X or H pipe. Without those pieces, you would probably lose scavenging. Even if you don't lose much at the lower RPM range, what is the appeal of the true dual for a street car? Besides the nostalgia of the old days when that was the way to improve performance?

WW7

I replaced the stock cat on my 89 with a magnaflow high flow cat . I don't have mufflers so the cat serves to quite the noise down on my 383 motor to at least a reasonable level..I tried it without the cat and the noise was way to much...The magnaflow cat only has 2 fine screens inside , and is so nonrestrictive you can look through the tube and see birds in the sky...really...Plus the magnaflow is less then half the cost of a random tech cat...WW

24yrold&86conv

My goal is just to fix the issue at the least cost, I don't race this, it's my only car and just driven twice at week tops. In fact, it is about to be stored for winter. I will still have mufflers so it shouldn't get to loud, right?

dizwiz24

Just bust that stuff up and shake it out.

Unless you have emissions to worry about.

Unfortunately i do, so i dont have that luxury! All my stuff is intact : (

WW7

with dizwiz above...For the cheapest fix just drive a rod or dowel down through the cat a few times to remove the guts..At least it will still look like you have a cat, and all it will cost is a little time.....If you still have mufflers it should only get a little louder....WW