offgrid

Hello all

We are just setting a mostly stock for know ls1 in our 82 blazer 4x4

I have short tube headers up front

I went down to my local muffler shop today and he told me not to go with duel 3" with x pipe as I will loose all bottom end output.

He told me either duel 2.5" with x pipe or Go with a 2.5" duel in duel out Thru a MagnaFlo that has an x pipe cross over built in it.

I have decided on using Magnaflo as I like its sound on several of the rigs I have seen.

I just do not know the configuration to go on the pipes.

Thank you all in advance.

leon phelps

make your choice then live with it.

asking here what we should do with your car is foolish.

asking the pros and cons of a setup is different, but you didnt do that.

Toddoky

His advise to you is valid and follows the laws of physics that we are all forced to live by. The size of your tubing should be sized to meet the mass flow requirement of your engine and no larger. Bernoulli's Principal clearly explains the inverse relationship between velocity and pressure inside a pipe...the higher the velocity the lower the pressure of the fluid traveling in it. Or, the smaller the diameter of the pipe is, the higher the gas velocity will be and the lower the pressure will be inside it. There is obviously a balance point here as you can't make the pipe too small or it will become a restriction to mass flow at peak power. A dual 2.5" system will easily support 400HP with much better low-mid rpm power making potential on your LS1 than a dual 3" system can offer, which is especially what you want with the type of heavy vehicle you're putting the engine in. Gas speed also decreases/increases with temperature, so systems without cats will suffer even more loss of velocity by going to 3" tubing than a system with cats will. You will be more satisfied with the end result I can assure you.

STEVE PWC

Dual 2.5 pipe will be more then enough for or motor. Good for 400hp. 3inch pipe 500hp

89gmcs15

iTrader: (7)

You talkin whp or crank hp?

offgrid

Toddoky and Steve PWC, Thanks for the help. Just wanted to know before I went to big. 2nt shop confirmed the same 2.5 is all that is needed.
Offgrid

Ian Johnston

I have a 5.7 LS1 in my 1978 C20, and am running headers with twin 2 1/4" pipes into a single 3". Only reason I went that way was the truck already had single 3", and the rest I got for nothing, and it matched up to my cats(from same type of car.)
If I ever redo it, I would go twin 2 1/2" all the way.
Got any pics offgrid?

the_merv

iTrader: (88)

I'd go dual 2.5"..nothing more is needed. If you do the math a dual 3" system is 44% larger than dual 2.5".

Dual 3" will easily support more than 500hp to the wheels..

offgrid

Hello Ian

If I could figure out how to I would like to post some as it is torn down
with only the cab on, ready to go to the sand blasters Sat. then over to the paint shop on Mon.