Cat-back...worth it?

brian12c · September 18, 2006

07 classic 4.8 reg cab - would a cat back system for my truck give me much power over a muffler swap?(single in dual out) I've heard mandrel bends really aren't necessary unless youre going to really soup it up.

Also, how difficult is it to install shorty headers on the 4.8? Thanks, Brian

thecraft · September 18, 2006

I can't help you with the headers, but I will tell you that a cat-back system will give you little or no power over a direct muffler swap. Mandrel bent piping is more of a marketing gimick than anything, you don't need new pipes unless your exsisting one's are damaged, rusted, etc.

And... if you are replacing a single-in/single-out exhaust with a single-in/double-out system, you will lose power rather than gain any, because your engine will have to push extra air through the system.

Indy · September 18, 2006

A cat-back system is definately worth it. I have a single in dual out system and it works great. I also have shorty headers. They are a piece of cake to install especially on a new truck. All the bolts haven't had time to seize up from heat and rust.

superbee · September 18, 2006

I can't help you with the headers, but I will tell you that a cat-back system will give you little or no power over a direct muffler swap. Mandrel bent piping is more of a marketing gimick than anything, you don't need new pipes unless your exsisting one's are damaged, rusted, etc.

And... if you are replacing a single-in/single-out exhaust with a single-in/double-out system, you will lose power rather than gain any, because your engine will have to push extra air through the system.

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How exactly would that work? The extra air part...

thecraft · September 19, 2006

Well, if you used really small output pipes, you might be fine (but then I'd bet it would sound like a rice burner). It's just that many of the aftermarket exhaust systems are like Single 3" In & Dual 2.5" Out. 2.5 + 2.5 does not equal 3, it equals 5. So it's like going from a 3" pipe to a 5" pipe. When that happens, the air slows down, and creates resistance to the fast moving air from the 3" pipe.

If you looking for great sound & looks and don't mind any possible power losses, a single-in/dual-out will be fine.

hyper7driver · September 22, 2006

Most of yout restriction is from your cats up atually. It's best to do an entire exhaust system. You probably won't notice much, if any gain from just a muffler alone, or even a cat back system. The same goes for the cats up, if you leave the stock pieces behind it. You'll need a good tune with your new exhaust system too. With the inceased air flow, you'll a little extra fuel too.

OnyxMAX · September 22, 2006

mainly for sound

you can gain over the stock muffler, but it's like 5-15 on a dyno. you won't lose power you can lose some low end, but it will be shifter higher in the rpm range. you won't realy notice it untill you run straight pipes or something. but your shorties would fix any lowend loss.

i hear some people complain to no end on smallblock header swaps others get it done in a hour or so.

95Sierra2500 · September 22, 2006

Well, if you used really small output pipes, you might be fine (but then I'd bet it would sound like a rice burner). It's just that many of the aftermarket exhaust systems are like Single 3" In & Dual 2.5" Out. 2.5 + 2.5 does not equal 3, it equals 5. So it's like going from a 3" pipe to a 5" pipe. When that happens, the air slows down, and creates resistance to the fast moving air from the 3" pipe.

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It's not quite that simple. It's not a direct add of the diameters, it's adding their cross-sectional area. If you work the math, a 3" pipe has an area of 7.07", and twin 2.5's have an area of 9.81". A 5" pipe has an area of almost 20".

That said, single in/dual out doesn't really create alot of resistance (most of that is taken care of inside the muffler, if it's a good system), and any torque loss (which is typical) is pretty minimal. The HP gain on newer trucks is pretty minimal too (as said above, 5-10 hp) because stock cat-backs are pretty free flowing, and most don't have to be altered/tweaked until you've got significant power gains over stock.