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Whats the best header for a XJ and question on backpressure.

X

XJ96Classic

NAXJA Forum User
Location
Newport Beach, CA
Like everyone else my headers cracked. What is the best header to replace with.

I'd like something that increases power. But I am wondering at what point does too free flowing of a system start to reduce your power by not having enough backpressure??

Anyone know the answer to this?
 
Backpressure smackpressure... How much backpressure do you think there is on a top fuel drag car. ZIP, ZERO, ZILCH.

Show me a dyno chart that indicates a loss in horsepower as backpressure decreases.

That's my two cents.
 
I dont think there's a hands down "best" header...I've seen every make/brand have complaints of cracking. If it gets hot enough under there, any header will crack.

Less backpressure reduces your torque, IIRC...

Lots of people went the cheaper route and got APN headers....some go to the high end and go wtih Borla or Banks - I think the debate still rages on as to which one of those two makes the better "high end" header - they both use different grades of steel and both claim their steel choice is better for various reasons....
 
JNickel101 said:
Less backpressure reduces your torque, IIRC...

quote]

Then why would anyone ever want a high flow on a Jeep. They are all about torque. who cares what hp you get over 3000rpm



---- as far as drag cars go.... that a different engine set up... have you ever taken the exhaust completely off of one of your cars before and driven it???? huge loose of power. they are designed to require backpressure.

i just want to know at what point go past what backpressure you need on a jeep and get into a area that you loose hp/torque
Click to expand...
 
While I can't say I actually drove a car with no exhaust, I did run my Camaro with nothing but shorty headers, and let me tell you, when I put the 3" single exhaust with flowmaster on, I was pissed at how much slower it would rev. It lost a lot.
 
which header depends on what year rig.

Banks headers seem to crack the most. Borla seems to crack the least. APN are cheap. Stock do ok. Thorley are pretty but still crack. The newer OEM ones available from the dealership have a flex joint in them and are rumored not to crack at all.

Make sure your motor mounts are good or you'll crack again.
 
Love2Ride450 said:
While I can't say I actually drove a car with no exhaust, I did run my Camaro with nothing but shorty headers, and let me tell you, when I put the 3" single exhaust with flowmaster on, I was pissed at how much slower it would rev. It lost a lot.
Click to expand...

That was all butt dyno. Theres no way a small block chevy was choking up on 3" exhaust, even if you had forced induction and were pushing 5500 rpm's.
 
it's not about "backpressure" per se. it's a lack of velocity. don't go bigger than a 2.5" pipe with a decent muffler and you'll be fine. it'd be pretty tough to screw up the torque on a 4.0 with a header that flowed too well. the new thorley header i saw looked pretty sweet, but it's pretty spendy.
 
Eliminating the backpressure on a stock engine kills cylinder scavenging and therefore torque. Bigger headers are great if you have other mods to increase flow but are not a benefit on an otherwise stock engine. Honestly on a stock 4.0 you're better off with an APN and better engine mounts (often the cause of cracked headers) like the ones from M.O.R.E.
 
cal said:
That was all butt dyno. Theres no way a small block chevy was choking up on 3" exhaust, even if you had forced induction and were pushing 5500 rpm's.
Click to expand...

Keep in mind this was 3" single to flow with tailpipe. It DID rev slower with the exhaust than with uncapped. Full roller with Dart heads and it frequently saw 7000rpm. :thumbsup:
 
Last edited:
You're lucky to have lots of options for the 96....i have a 2000 and if I want anything other than stock exhaust manifold, my only choice is Banks.....$400....
 
Tenhigh and Jeeperjohn are both in the correct ballpark..a stock 4.0 will do well with 2.25" pipe. I run a 2.25" pipe with a dynamax and hi flow cat...the engine pulls strongly to redline...you dont need any more than that.

Save the trick exhaust for a stroker or other serious mod like a supercharger.
 
Last edited:
I like my Borla header/downpipe with my Dynomax hi flow cat and my 40 series Flowmaster muffler. I have run this for 6 years with no problems. It helped fuel economy and power. I gained about 1 mpg with this set-up. When I bored the taper out of my throttle body that was the icing on the cake.

Light throttle response and torque increased dramatically, the transmission no longer hunts between OD and D on hills. Top end power was also increased, and no fuel economy was lost unless I'm hammering on it.
 
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