Going in Tues for my exhaust to be done on my 08 5.7.

Just a few questions before I go. I am most likely going with a magnaflow SI/DO (either both out the back *or* one on each side behind the wheels...not sure yet).

Anyways,
I am figuring on going 2 1/2 pipes out. Sounds right, right? And a 18 inch magnaflow what most of you are running?
As for the y-pipe.....I read that many people said that they are restrictivce. I am unsure how much this place would charge to change it around, but I am basically putting on my exhaust for look, sound, and mild performance gain/mpg gain....should I really consider looking at getting the y done?

thanks

 

The stock exhaust is 3". Just remember that if you have a place custom bend an exhaust you will only be getting mild steel vs the Stainless that came from the factory.

 

Straight 3" Stainless True Duals

 

I'd leave the Y-pipe alone...it'll be expensive to have tru-duals put in or a X/H pipe fabbed. And if you're going to do that you'll want two SI/SO mufflers.

 

i wouldnt do straight pipe. it just make LOUD noise. it does give less restriction but sounds of straight will be horrible on hemis

 

right now iv got dual 2 1/2" straight pipes, but plan on dual 4" straights

 

Exactly.... and they look sweet

 

dual 4" straight pipes?? thats huge. i would think that would be way to big and the engine would loose from that, having little to no back pressure at all. I may be wrong. but.....

i personally went with a single 3inch in to dual 2.5 out flowmaster 40 series. custom fab exiting out the sides behind the rear tires with 3inch slash cut tips. It sounds awesome and is very loud. alot of drone on the highway but i love it and also had the resonators removed. leave the y-pipe alone for now. maybe down the road if you want to get headers then get a high flow y-pipe with new cats and so on......

 

Well given that your initial pipe diameter is only 2-1/2" at the flages and then opens up to 3", 4" is a little extreme. Besides the bigger you go and the less restriction you have past a certain point significantly reduces low end torque! Sure you gain top end hp, but it's not worth the amount you will lose off the line which is where you are most of the time. The only reason guys at the track do huge exhausts and dumps is to keep the head ports cool at higher rpms and keep the flow up because at the track your engine is mainly running from 75%max rpms to max rpms.. Not a good idea to go 4" duals.

 

so what would you say then 3" is a good choice, i would like a bit bigger then i already have