4.0 header cracking answer

[aaronkeiser]

After I tore down my motor in my YJ it was no surprise that the header was cracked at pretty much every joint. I bought a new APN header to go with the new stroker and just yesterday I had a muffler shop chop off the 2.25 collector and weld on a nicer 2.5. While I was there he told me the reason the jeep headers crack so much is because of torque. The header is so stiff and the exhaust pipe it's bolted to is also very stiff that under hard throttle it flexes the header causing it to crack. He suggested, from is experience that I cut some of the welds on the header flange to help relieve the tension. Possibly the reason I just stated and heating and cooling would cause the stock headers or any header to crack over time. Possibly building these engines to produce even more torque isn't helping either.

[Flash]

I agree........................Except for the cutting of the welds.............


My used Borla Header came with a collector(goes from header to cat,) and a clamp that goes around the header and mounts to the tranny bolt. this eliminating the eng TQ from pulling on the header.


Flash

[BADASYJ]

Ya, I would not cut any weld, they are there for a reason. They do make a flex fitting for exhust pipes. That would stop the cracking.

[5-90]

My approach would be:

1) Make sure all of the engine mounts are in good condition. All three of them. (Most header cracks that have been reported to me have been accompanied by engine mount failures - often noticed after-the-fact, when I bring the subject up.)

2) Install a flex joint of some variety in the downpipe. Yes, this probably means just getting a new downpipe bent to make room for the flex, but it's money well spent. Especially if you're lifted - you can also get rid of that OEM crimp in the OEM downpipe, and open up your exhaust just a touch more...

[stogie25]

I recently fixed my Banks header that was in the same shape. We welded on a flex pipe in line with the exhaust to hopefully stop it from cracking again. 1 month, so far so good.



Good luck,

[stogie25]

Sorry about the moved image.