Topic: Purchased new header for the YJ

[Bikerjr1]

I ran across thiese on Ebay and the price seemed good. (http://cgi.ebay.com/ebaymotors/Jeep-Wrangler-YJ-Headers-91-92-93-94-95-2-5L-88741-/300471780737?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AJeep&hash=item45f5838581).  I couldn't justify the cost of all the others that I've seen.  Dynomax makes the Blackjack headers.  I've run them on a Ford 360 with a bunch of 390 parts and they worked and held up great.  If this one works out as good I'll be happy.  There are 4 left right now.  Down from 10 a week ago.  When this gets here I'm going to change the cat and muffler.   Hopefully I can get my bigger injectors cleaned out and running by then, using the stock ones for now.  And finally put my CAI breather and tube back on.

My main concern is the cracking of all the other headers.  I read the posts about high exhaust temp causing it.  If that was truly causing it wouldn't the factory 4.0l "header" be cracking with the same regularity?  just thinking off the top of my head .  Could vibration and flexing on the motor mounts be causing it?  I'm basing this on some I've seen of 2-1 Harley-Davidson headers.  I know the bikes were running very lean, no carb changes,  rubber mounted motor and hard mount at the tail.  Same problem crops up on Gp bikes.  I know that the exhaust pipe is rubber mounted but that is still a lot of weight to be flexxing around.  I'm looking at posibly a short flex pipe before the cat and a brace at the collector to the block to take the strain.  I'll try and remember to take some pics when I install it.
JR

[st.chevrolet]

It's very common for factory 4.0L headers to crack, I have changed a few of them. That's probably why they changed to a cast iron exhaust manifold around 2000.

[dwtaylorpdx]

Yea but the 2.5 had cast iron and they crack all the time.... 

almost 12 years on my Thorley Header and no cracks.////  So far.

Went through two stock manifolds.

I do break the read header stud off about once a year...
Last time IN used a jam nut and kept teh torque light on the studs so far so good.

Dave

[sharpxmen]

I ran across thiese on Ebay and the price seemed good. (http://cgi.ebay.com/ebaymotors/Jeep-Wrangler-YJ-Headers-91-92-93-94-95-2-5L-88741-/300471780737?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AJeep&hash=item45f5838581). 

that's a pacesetter header although they list it as Dynomax - i can bet you there are stepped washers in that kit and had a 1 piece intake/exhaust gasket (that's what my pacesetter came with). Good price though, nice find.