I have a 92' firebird with a 305TBI - I recently purchased some hooker headers with a 02 sensor hole. I have been asking around work and a older mech. said that my 92' has to have back pressure to start.
My plans are to put headers on and run dual exhaust eliminating the catalytic converter to assure un-restricted flow. I plan on using the stock 02 sensor.

so my question is what do I have to do or change to install headers???

 

Your plans sound fine to me. There are thousands of these cars out there with headers, and they all start fine everyday....can't see why yours would be any different.

- Justin

 

He mentioned that because if you run shorties with no Y for a while its possible to burn up a valve. I would seriously rethink your idea of duels. For a 305 TBI a regular catback is MORE then enough.

Is your headers for thirdgens? what make and part number?

 

I'm planning on doing roughly the same thing, headers, no cat, and to save money for a while, no mufflers. It isn't a daily driver, only gets taken out on a nice day for less than 100 miles. Will that burn up valves?? I was going to go with the shorties. What can be done to prevent valves from burning up? Sorry, not trying to steal the thread

 

You don't need back pressure to start. You don't need back pressure for anything.
You won't burn a valve.

 

1) I'd stay away from "the older mech."
2) I'd do lots of reading/searching on here and see what others have done etc.
3) If after reading and searching you still want duals for your 305 or you don't want a 350 start at #2
I think you'd be fine with a nice set of headers and a quality 3in. catback with the 305....now then if you plan on building a 305 for the track like some on here have done....and had good results with then that is different.Or if in the future you see a high horse power engine of anykind,but if a mild 305/350 is all you will be doing to the car then duals are no better (as far as flow) than a nice cat back and headers.
Good luck,
Mike

 

If you're removing your cat then you dont care about emissions, but you should know the TBI cars use a normally open EGR valve, and uses the backpressure from the exhaust to keep the valve closed. With a wide open exhaust, the EGR valve could be hanging open a bit, causing a code 32 SES light, and other such maladies.
Dual exhaust is not worth the hassle and cost on a thirdgen street car, as there is very little room in there to begin with. Yes, many people have done dual exhaust and it does sound better. But, an aftermarket 3" exhaust and 3" cat is more than enough flow for a TBI 305 engine, and less expensive than a custom dual exhaust setup.
Lastly, I always have to say that removing your catalytic converter and other emissions devices on a street car is a FEDERAL offense, regardless of your state's emissions testing laws. If you're caught (and that is a big if), you could face a hefty fine, and/or jailtime. It also tells clueless politicians that we hot rodders dont care about laws and emissions so they make up more restrictive laws, like what is currently happening in Pennsylvania.

 

Is there any kind of performance gain if I take off the Catalytic Converter vs. leaving it on.

how much does a cat-back system cost?

After reading the replies I am thinking about not going for the duels--

I am always reading about how people go with duels and catback systems.

Question- Would my stock exhaust system be adaquate for my headers??
What if I went with stock and eliminated my cat. convert?

Thanks for replies -

 

removing the cat does this;
better flow = more hp
better sound (like a boat, nice....more throaty)
smells cooler too, again, like a boat
It's slightly better than using a high flow cat, but more importantly, it's a heck of a lot cheaper. Up here it's not a "federal offense", so I can recommend it, but i'm wary about suggesting it to you, lest a group of angry tree huggers pelt you with pine cones....

Look up different cat back exhaust systems, check summit, price it out for yourself. The headers are the big HP gainer, then the rest of the system follows closely. The whole piping system is weenie small, if you can, go headers & catback, and you choice for the "catalytic convertor".

edit; check out urbanhunters sticky on cat backs - THANKS URBANHUNTER, rock on!

 

would the stock 2 1/2 in. stock exhaust with no cat. with stock muffler be good?

Would changing the stock single to dual muffler help with better flow? With cat removed

Is a single 2 1/2 pipe adaquate for a stock 305 with headers

 

Just keep the cat, it will make very little difference, cause you hassle down the road in terms of emissions, and IMO exhausts sound worse cat-less. More popping and raspiness.

As others have said, stick with 3" piping, a high-flow cat, and a muffler of your choice. Mufflers do little except change the sound of your exhaust; personally I like Spintech for a not-too-loud but throaty sound.

 

I'm in Michigan. I have headers, y-pipe, and 3" "straight" pipe on my TransAm. I love the sound. Only problem is...unless your doing this yourself, is trying to find a place to put the exhaust on with no CAT. I went to Maxi muffler, bought a factory 3" pipe, bought 2 18" stainless steel tips, & a flowmaster muffler.
Then I had a friend who works at a muffler shop put it all up for me. I already installed the headers and Y pipe. So I drove it to him like that. (Yeah it was loud.) Everything bolted right up. All he had to do weld in a 3" pipe to take the place of the CAT and I was good to go. Oh and make duel pipes coming out and weld my new tips on. But it sounds great!