4.2L Headers

[novajoe]

Originally Posted by efi-diy

Joe,

Are they leaving the rest of the exhaust stock to get a 1:1 comparison or is it getting an upgrade as well?

Yes the only thing that is being changed is the header and cat.

[efi-diy]

Good, then any change will be from the header/cat. Are you going to dyno it with after the headers are installed without touching the tune?

[novajoe]

That is what we talked about yesterday, and I was told that was the plan. The begining of next week the TB should be back to PCM of NC. They will use the information they collect to make the great tunes they are already known for. So if you have the headers on order you may want to give them a call so you can get the new tune and take full advantage of the headers. I will keep you up to dateas I get more information. I am very excited to see what PCM of NC can do with this set up. I may also have to get their electric fan conversion while they have it at the shop.

Quick video of the TB at PCM of NC.

http://s246.beta.photobucket.com/use...e9b79.mp4.html

[efi-diy]

Joe,

The VVT table has 0 retard at higher load (rpm/map) - most of the overlap is down low for EGR purposes. Taking that out will help low end torque, and adding it in up higher should result in HP increase.

You might want to mention this to them.

If you can consider getting a spare head and re-working the exhaust ports - there is 25+ HP bottled up. The 06 up exhaust valves are 1mm bigger and will help.

With the head reworked this becomes a 300+ HP engine - take out the TM and enjoy the ride. GM tuned this for socer moms not the race horse it really is.

[novajoe]

I would like to do the head swap down the road

[Nexus1155]

Maybe after getting the head reworked it might be better, but I noticed when futtsing around with the retard down low it felt like a Honda trying to hit VTEC. Lost a little low end for some reason. Almost a hiccup/hesitation. Advancing it in the higher RPM range though to 25* as you said a while back made it a lot more fun to drive.

I'm excited to see the results of the header though.

[novajoe]

A couple pics of the header build.

[XUVFISCH]

I was reading a bunch of threads on the manifold crack (after my Envoy just got really loud over the weekend) and found this thread on a header for the Envoy.

I'd rather put on a header for some more money then replace it with the same. + extra HP, is always needed.

How long till one is available for purchase and a final price on it? Will it come with bolts, gaskets and everything needed for direct install? I probably will not be doing the repair till spring, so I have some time. How does PCM of NC go about the "new tune".

Thanks for any answers you have.

[efi-diy]

4 days - no updates.. wonder if they found something on the dyno that they didn't expect...

[novajoe]

Nope it hasn't made it to the dyno yet. I talked with Chris at Kooks and there was a small set back they had to work out but I was told that they should be done this Friday. Then it should be off to the dyno.