Kook's I6 header installed


Original poster
Dec 17, 2011
Got around to installing the header this past weekend. Here are some things I noticed on doing the install. First, a big thanks to Fishsticks for his writeup in the vendors forum. Secondly a thanks to Kook's for resolving the fitment issue with 2006 and newer trucks. A few things to add to Fishstick's procedure:
1. If you have access to a torch, heat up the three nuts that hold the cat to the exhaust manifold and the two nuts the hold the muffler to the oulet of the cat pipe. These are usually rusted and siezed to their respective studs.
2. Before doing too much, make sure the oxygen sensors are not siezed. My front one wasn't but I destroyed the rear one trying to remove it. I had to drive for three days before I could get a new one with the cel on. Maybe just get two new ones and not worry about it. If you reuse the old oxygen sensors, make sure you put some antisieze on the threads before installing them.
3. Antisieze the slip joints where the Y pipe connects to the header collectors and also where the cat pipe connects to the Y pipe. Same for the bolts that secure the headers to the cylinder head.
4. I had to raise the back of the trans and lower the crossmember to get the cat hanger out to remove the cat from the truck. Maye 2006+ are different than the older ones???
5. The heater hose is a little too close to the #6 cylinder primary header pipe for my liking. I insulated it with some firesleeve. I don't want to take a chance and heat fatigue the heater hose causing a coolant leak.
6. There seems to be a lot of heat radiating off of the header as compared to the o.e. manifold. I also firesleeved the a/c hose that goes over the front primary header pipes. This may not be needed, but I fell better having done it.
7. After a few heat cylces, retorque the bolt that hold the headers to the cylinder head.

After a few days of driving, I hear a bit more engine noise. Not a louder exhaust noise, just engine noise. I attribute this to the header not having the sound absorbing properties that the o.e.m. manifold has. I've installed many sets of Kook's headers on C5 and C6 Corvettes, all without any issues. All in all, Kook's has made a great product that actually fits without any issues.

Maybe if I get bored, I run the TB on our dyno.....................


Original poster
Dec 17, 2011
Honestly, there isn't much to see after everything is in place. But I can take some this weekend after I do the retorque of the bolts.

Boricua SS

Nov 20, 2011
totally off topic... but love your avatar!!! I have a German Shepherd myself :yes:


Mar 16, 2013
I'm glad to hear you like it. I don't just recommend Kooks but I have them on my own vehicles as well, it's a nice quality product no matter what your platform.

And yes you definitely will notice more noise with the header than the stock manifold. The manifold is really thick and absorbs a lot more sound than the thinner steel of the header.

Definitely a worthwhile modification!

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