i have heard from a few people they thought getting headers on a 4.0 sohc motor is kinda a wasted. They say it took away some torqe.
I am debating on getting some. I had 3 cats taken out and left the two with the o2 sensors on them. It runs through a 3 inch pipe to a flowmaster dumped. I also have done the air box mod. I really would like to get a bama chip but i am debating wethere to get the headers or not before i get the chip. I am running 35 with 456 gears and a posi. I dont want to lose to much torqe since i need it for the dirt. I feel if i let my truck breathe more then it is right now, i won't get enough back pressure just from that flowmaster. No back pressure equalls no good. What do you guys think

 

i would think that you lost more by removing the 3 cats. why would you do that and why would it help?

headers are gonna help more then removing the cats like you did. i havnt heard of anyone loosing power because of the JBA headers. they are a good product, its just they are not hte biggest bang for your buck like the Bamachips programmer.

if i had the money i would get them, and i prolly will get them. sooner or later.

 

his biggest mistake was running 3" pipe and a flowmaster...then dumping the three cats...

go to JBAs website and look at the dyno sheets. that'll tell u what u want.

 

on a stock motor...not so much..

 

im sure they help, but i always thought that they are a little expensive.
and i agree, im thinkin you have lost a ton of back pressure
takin off the cats and the three inch pipe. that may have been a little much

 

wow you had 5 cats? wtf? Buy JBAs and if u want a set lemme know!!!!!!!

 

no no no...

backpressure = bad
removing restriction in exhaust = good
going to large in pipe diameter = bad

backpressure is not good, at all. its when u up the pipe diameter to much u loose the exhuast velocity. that is what causes low end power loss. modern day cats are a fraction of restricition as they once were so removing them is silly.

 

For modular engines backpressure is imortant!!!! BACKPRESSURE!!!! u need a somewhat restrictive exhaust, whether its two high flow cats and a magnaflow muffler or two stock cats and a borla. If you run it out in front of the tire(eliminated exhaust over axle) you will absolutely love the results!!!!

 

and why is that apply for modular engines and not pushrod engines?

 

well it does apply for pushrods as well, but the torque curve on mod motors is more up top and if u lose resriction down low, you have no torque until about 3500-4k rpms...

Look at it in this perspective... Motorcycles (Yamaha for example) have an exhaust valve called EXUP. It is closed until the rpms are in the middle of the power band to allow the backpressure to build torque. You cant have no backpressure at all and gain from it unless you live in a perfect performance world!!!

 

Get the cats replaced, drop the pipe to 2.5" and then get the header's and you will be good.

 

Exactly

 

 

why did i gain by not enlarging from stock, but coming out infront of the tire and losing two cats? how many of these comments are backed by realtime dyno charts?

 

uh, if i understand u correctly, u are saying what i already posted. stock or one size larger then stock size and no restriction = power gain.

 

on my mustang they recommended i got a bigger pipe from the 2 1/4's to 2 1/2's. Is that good or bad???

 

how is it gunna be ran? with an X-pipe?

 

http://www.veryuseful.com/mustang/tech/engine/exhaustScavenging.pdf#search='backpressure%20in%20 exhaust' Here you go.

 

I dont think you are reading my post right. What I am saying is that backpressure is a must for modular engines. I removed only two cats(meaning still two left) for better flow but still have backpressure. It is important!!!

 

i think we agree to disagree. u cant get away without any restriction in an exhaust. there is always some present untill u run a straight piece of pipe off the header.

in the ideal world, the exhaust system would change diameter to meet engine rpm. smaller at low rpm and larger at high rpm.

im still unsure how backpressure would help a mod motor, unless the cam profiles are such that they need it. just like a header is supposed to help scavange the ehaust gas from the combustion chamber and equal out the exhaust tone pulses, a properly sized exhaust system does the same.

bottem line is:
-ack pressure isnt good.
there is always some form of backpressure in a legal exhaust system.
increasing pipe diameter more than one size over stock on a stock or mild engine yields torque loss down low, why? because the velocity and scavanging is throwin outta wack.

until u can prove to me how a modular engine needs some back pressure, i stand by my guns. not saying ur wrong or right...

back to the initial question, headers are definatly worth it. they are basically tuned pipes to allow the engine to efficently expell the exhaust gases by improving scavanging.

 

im still debating whether i wanna run an xpipe or h pipe which is better?

 

yea whatever, i ran true duals into a magnaflow true-x muffler. it has an x-pipe built in

 

idk some say its good some say its bad, i dont understand it, even after reading this post.

my truck 03 ranger with the 4.0, i had a SI/DO magnaflow, 2.5 in dual 2.25 out i lost alott of low end power(sure did seem like it). i changed from that to flowmaser but then to borla which is my current setup. SI/SO 2.25 and it runs great. good low end, mid and high, i have no complaints with it.

id maybe i didnt have my "ratio" right or something.

 

I know on my old 4.0 OHV, when my muffler fell off (read, rusted away), I lost alot of getup and go. When I put a muffler back on it, it felt alot quicker.

 

What about on a 3.0L is a single pipe 2.5 inch from the cat back decent? Still going to be running some type of muffler. I was looking at the JBA evolv stainless system.