Headers/Exhaust....point me in the right direction

**ElAlacran2010** · 04-13-2011

Ok. So i'm about to install my speed daddy headers. My issue is that i have a slightly modified exhaust, resonator/u-bend delete, but where do i reduce to the stock exhaust pipe size. I believe it's 2 1/2in. The downpipe exits at 3in. If i dont install a hi flow cat and use the stock cat, will the restriction now be at the cat? If i delete the cat and do straight 3in pipe and reduce after the o2 sensor, will this be my best bet. I only ask because everyone has a different opinion on what to do. I really dont have the money, but i've had these headers in my closet for almost a month, and im gonna do whatever it takes to install them by saturday! I just wanna know what would be the most efficient way to do this.

**matt5112** · 04-14-2011

well if you had the flange deleted then you're in for some fun.

stock cat isn't worth putting back in.

They clog.

**machinegunsquid** · 04-14-2011

Umm...If the cat-back flange is gone, you'll probably end up having to install the headers, and run it open downpipe until you can get to a shop that will weld it up for you.

Dont reuse the stock cat..sell that *****.

And if you're state doesnt have emissions, go catless, if it does, then well..get a cat...

**BillBoost37** · 04-14-2011

Orrrr ya could just pick up the parts you need to connect it .....ahead of time.

The headers you have in your hand, so finding out if it's 3inch OD or ID is really easy. You likely can't find a reducer to the stock 2.25inch size pipe from a 3". Some exhaust shops will make one for you super cheap. But that's a large difference. Another idea is to get two adapters. From 3 to 2.5, then 2.5 to 2.25. A couple of clamps and some planning and it'll be fine until you get a different catback or have more work done.

One of the three installs the other week had this issue. An extra 30 min of parts hunting and it was cleared up.

**ElAlacran2010** · 04-15-2011

Well I just removed my stock manifolds. Got everything prepped to put in the new headers. Except yeah i need to cut the pipe now since i removed the flange. I decided to go with straight 3'' pipe no cat. Im gonna reduce after the O2. Thanks BillBoost for the idea to reduce from 3'' gradually to the stock pipe size. I just hope i can deal with that catless exhaust sound. If not i guess im gonna buy the cat ASAP! Broke but content....

**BillBoost37** · 04-15-2011

That works. Keep in mind that dropping the back of the subframe allows you to wiggle the rear header into place. Get it held on and then lift the subframe, mark where the O2 will hit on the tunnel edge. Pull the header back out and make the firewall/tunnel edge move and put the header on for good.

Coming from the Bonneville world is nice because nothing was made for that car. There's no catback flanges to bolt up to.. it's all make your own, think outside of the perfect situation box and come up with solutions.

When someone says can't, my mind starts to think and look at the problem. There's an answer for every question, the challenge is finding it.