Ok i got an 87 iroc 305 tpi, bone stock other that magnaflow exhaust. I was thinking about taking the cat off. Will this give me more hp and better gas mileage? and some of my friends say my car is too quiet, so would this help with all that? if i do decide to do it, can you just get a 2 3/4 pipe and just swap it out using the stock clamps so i can just swap it if i have to get it emissions tested? thx

 

Much louder

 

little off topic but on my grand prix gt cut cat off i gained like 2 mpg lol but i have no clue with your motor

 

It'll be louder and if it's the original cat you will likely see HP and MPG benifits. Older cats were restrictive (the reason the top of the line cars had 2) and they get worse with age.

You could invest in a quality replacement using newer technology and not lose any real HP or MPG but the straight pipe is the cheapest route if you done need to pass emmissions.

If you have to submit to a sniffer test then you might as well spring for a new cat since your older one will likely fail or be borderline at best.

If you ever run race gas or leaded gas be sure to pull the cat or it'll likely be ruined.

 

It should free up a few hp. Stock cats probably don't flow too well. However your engine might not be making enough hp so that cat is a restriction. When 350 v-8 cars received dual cats, they were rated at 10 more hp than single cat 350's. It's a low cost mod so I say try it out : )

A certain amount of air flow is needed to support desired hp level. Here is a neat article on cat flow testing for 99 LS1. I wonder if anybody knows what single stock cat flows for our cars?
http://www.installuniversity.com/ins...n11.122001.htm

 

I dont think youd notice a whole lot powerwise with a stock 305 + stock exhaust. It will be a bit louder. With a full 3" exhaust + aftermarket cat (or no cat), you would notice some gains. A single cat can be restrictive, depending on what engine you have. With my old 350, the full lenth 3" exhaust, flowmaster single inlet/outlet + single 3" cat would make around 8 PSI gauge of backpressure at 5000 RPM. Thats about 220" of water, or about 10x the recommended in that article. Needless to say, with a higher performance engine, they can be restrictive, and are best left off if possible. The other option is to run two large aftermarket cats, but space is limited under these cars.

 

I have a stock 89 camaro 305 tbi. i put duel flows with no cat and its was like music to my ears . i noticed some gains in power, but not a hole lot. but i advise if you let it breath at the back to need to let it breath at the engine. maby pick up a nice air filter and some comp headers

 

I like the smell difference. It's like a boat idling. And yes, it sounds different. A slight bit louder, but more... open mostly. It will have more of a throaty sound at lower RPM.

 

I agree Sonix, nothing's quite the same as that tang of raw fuel in the exhaust.

Could Camaro Man not just hollow the cat out with a broom stick and put it back on with all the catalytic material knocked out? That way it would pass a visual inspection. No good if your area does a sniffer test though.

 

Smells very different, smells like a lawnmower. A little louder with a little more resonance.