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Mandrel Bent Downpipes?

JoeyBottles

NAXJA Forum User
Location
Fall River, Ma
I'm having anxiety about finding somebody who does mandrel bent stainless downpipes. I just bought a header with a 2.5" outlet... I want to run 2.5" all the way out the back... But it seems no one in New England does Mandrel bending? Hell I can't even find anyone who does 300 series stainless... Any suggestions? And websites that will custom build?
 
No local shops have mandrel benders?
 
Muffler shops don't buy mandrel benders. They are very expensive. The only way to get a custom mandrel bent pipe for a Cherokee, is to buy an aftermarket one, or find a shop that will weld one together out of pre-bent mandrel bends, from a place like Summit Racing, or an exhaust parts specialty supply house like Columbia River mandrel Bends ( http://www.mandrel-bends.com/catalog/ )
 
I'm having anxiety about finding somebody who does mandrel bent stainless downpipes. I just bought a header with a 2.5" outlet... I want to run 2.5" all the way out the back... But it seems no one in New England does Mandrel bending? Hell I can't even find anyone who does 300 series stainless... Any suggestions? And websites that will custom build?


What year is your XJ? Mine is a 2001 so not sure if your downpipe is the same but I just bought a 2.5" clifford performance header and used the walker downpipe/cat assembly (has two converters inline) which was 2.5" also and worked perfectly.

http://www.amazon.com/Walker-52304-Certified-Catalytic-Converter/dp/B000VKYCQM

As far as the front pipe (piece that attaches to the downpipe and snakes around to the back), I had a shop bend that.
 
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I totally understand why you want 2.5" stainless straight out the back, mandrel bent & full of win.
Let me make a couple counter points, though:
If you remove every last bit of the Jeep's exhaust restriction, it still won't be much faster than stock. On the low end of noticeable. Ask me how I know.
At stock height, a 4wd jeep will turn it's front pinion & driveshaft into exhaust-maulers.
The restriction at the header pipe isn't such a bad thing, either - it tunes the exhaust flow to start scavenging around 900 RPM. remove restriction, move that figure higher (as well as increasing peak). So your off-idle gets slightly weaker even as your peak goes higher.
Looking back at all the PITA I've had with header pipes on this rig, I wouldn't have bothered if I'd known. The cat & rearward, sure : but I'd leave the header pipe alone.
 
My xj is a 99;

So you're saying that the regular walker down pipe would be sufficient? I plan on upgrading to a stroker which is why I wanted the 2.5 Mandrel etc.
 
If I'm remembering my numbers correctly, always a gamble,
the factory exhaust is 2.25" all the way from header collector to tailpipe but with some crimpage in the down pipe that necks it to like 1.75", this was done to clear the driveline. With lift, you don't need the crimp in it.
With a stock 4.0 (bolt ons, no internal work) I mated a 2.25" down pipe to 2.5" cat & cat-back. From cat rearward, this should support up to ~250 HP without undue restriction. A 2.5" down pipe is going to net you a few more ponies on the top end but through most of the power band I don't think it's necessary.
If the walker piece is 2.25 and isn't crimped, I'd take it, then go 2.5" for the cat & rearward.
 
OK... Well I'm really confused now... The header I bought from crown seems to be 2 1/2" but states it will bolt up to facTory pipe? I'm just afraid the aluminized pipe will rot out quickly...
 
If you are building a stroker and will have extensive head work done then a larger exhaust pipe may help. I believe if you do not do extensive head work then a bigger pipe will hurt your lower end as was stated.
 
I plan on doing a stroker when this motor dies... Or in two years... So I wanted to do this in one step so to speak... I think I'll just end up going with the pressure bent 419 stainless. Although I really want 304 mandrel...
 
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