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Discussion Starter · #1 ·
The Gen 1 SBC 350 in my K25 has one cracked stock exhaust manifold, and as a replacement I’m considering the Hooker iron manifolds (Hooker 8525HKR). Probably not that much better flow than stock, but I want something durable, and these do have bigger 2 1/2” outlets. If I used headers I would probably need something like the Hedman Elite with thicker flanges and tubes, and they are a lot more expensive.

In a couple reviews the posters mentioned difficulties with getting these to stay tightened down to stop leaks where they bolt to the head. I’m confused because it seems Ike it would work the same as the old stock manifolds. I also have aluminum heads and want to avoid tightening them down too much and stripping anything.

Could it just be poor gaskets are supplied with the manifolds? I use off-the-shelf gaskets from Autozone with my stock exhaust and have never had leaks.
 

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I’ve run the same set of Sanderson headers on my 350 for 25 years. Seems like pretty decent durability to me and not my first long term durability exposure to headers. Except for the rigors of racing I haven’t experienced any long term durability issues with headers at all either personally or with my customer builds.

Things I’ve noticed is when first mounted they may take upwards of a couple years to stop blowing gaskets unless further installation action are performed. In regard to leaks the choice of gasket makes a difference where the fiber or fiber in screen are the most failure prone and need to be replaced when they do blow. Stamped soft aluminum and better yet copper are more resistant to blowing or burning when a leak does occur. To fix these usually just relieving the fastener clamp load then retorting them puts the problem to rest for a long time before needing to to it again. Like I said above this eventually goes away as the headers restructure their internal fabrication stresses with repeated heat cycles. The thick carbon, carbon gaskets are pretty much bullet proof regarding periodic leaks almost set and forget.

I have found that including a flex section in the connection of the collector to the head pipes works wonders in reducing to eliminating thinks like cracked cast manifolds or header flanges and tubes as well as pretty much eliminating gasket sealing issues. Observation indicates to me that a major cause of these cracking and sealing problems is the combination of heat cycles with differential movement of the engine on its mounts to the exhaust system hung from the chassis. I found that this works equally well with a section of about 2-4 inches of cheap flex exhaust pipe as a bridge to the head pipe with screw type exhaust system band clamps or the showy and expensive stainless overbraid flex joints.

Bogie
 

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Discussion Starter · #3 ·
You bring up a good point about including a flex section in the system. My head pipes are bolted solidly to the stock exhaust manifolds and the only flex in the dual exhaust system mounting is the relatively short rubber hangers. The balance pipe adds even more rigidity to the system because both sides move as a unit.

My truck has straight axles, heavy duty springs and 10 ply rated tires, so the unloaded ride is fairly rough. I'm not worried about full length headers actually failing/leaking, but assume good 3/8" flanges will be needed to keep it all tight during the rough ride. Any leaks in the flange area really screw up the readings for my wide-band AFR gauge, and I rely on it to make sure everything is working right on the engine. Those Hooker cast iron manifolds seemed like an intermediate choice that might work well.
 
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