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Old 08-03-2013, 03:12 PM   #1
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Cast exhaust manifold or tube type header? 98TJ 4.0

maybe a silly question but is the factory exhaust manifold a cast iron casting-or- a tube type OEM header?. My 98 TJ w/4.0L engine has a steel tubing type header. The origional owner was not into alot of the performance parts. maybe the OEM cracked (if is was cast iron). The gasket at the intake/exhaust on head looks like it was replaced. The head was not. Did the OEM have crack problems?

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Old 08-03-2013, 06:15 PM   #2
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Tube type and yes they have cracking problems. Mine did but it's a 99. I believe it is the same as your 98.

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Old 08-03-2013, 07:49 PM   #3
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your 98 came with a tube style exhaust manifold, it is known to crack. late model (00-06) manifold are a 2-piece cast design and eliminate the problems for the most part.
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Old 08-04-2013, 04:23 PM   #4
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You can find headers on ebay for relatively cheap. Try to spend the few extra bucks though and get the stainless steel, and the one with the flex tubing in it so it less prone to cracking.
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Old 08-04-2013, 09:22 PM   #5
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Where does the crack happen at? I can weld any steel and stainless. Is it a support problem-or stress from expansion/contraction? Or is it "better to get an updated header" thing?
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Old 08-04-2013, 09:27 PM   #6
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It's better to get a revised header, one that includes flexible steel joints at either side as shown below like you can buy on eBay or Amazon.com

Welding the cracks will only help temporarily, the header will simply crack again right next to the welds. Engine torque is the root cause of the cracking which is common for '97-98 TJ 4.0L engines. Jeep fixed it in mid-'99 or so by adding the below-shown expansion joints.

The flex joints added in later designs to prevent cracking are highlighted in red.
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Old 08-04-2013, 09:49 PM   #7
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Quote:
Originally Posted by kawzak View Post
Where does the crack happen at? I can weld any steel and stainless. Is it a support problem-or stress from expansion/contraction? Or is it "better to get an updated header" thing?
it's an expansion/contraction thing. cracks usually occur at the collector where there is the most leverage from the head expanding/contracting.

the best idea is to convert to a late model style cast manifold. you can grab the two piece-cast manifolds off an 00-01 XJ or WJ, then use Walker Exhaust #52317 to adapt it to your cat.

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