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2008 gmc envoy_denali
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75 Posts
Discussion Starter #1
New to me '08 Envoy Denali with a 5.3. New FloPro 3" in/3" out muffler, resonator delete and a dual wall stainless exhaust tip. The truck sounds good. Nice throaty rumble at idle and the sound ramps up as the RPM's get up around 1800-2000. Makes you look when stomped on from a light. Just what I wanted.. Only three problems. Broken manifold bolts... 2 on the drivers side and one on the passenger side. Time for headers? That's what I'm thinking...
Mark
 

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2006 chevy trailblazer_lt_ext
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197 Posts
Broke at the flange (exhaust) or at the manifold (engine)?

If at the flange, those are threaded studs that can be removed. You may find that MIG welding a nut to the stud may help break it loose. The heat from the welding should start to break down any rust. Use some penetrant to help. I’d try to avoid destroying the OEM manifold. I’ve not had a lot of success finding OE exhaust manifolds. Aftermarket is basically junk in my experience.

If you’ve broken the bolts off on the manifold side in the head, you’ll want to use a bolt extractor and re-chase the threads. You can also try the MIG method above. Next time just get an OA torch and cut the bolts off the studs. Then chase the threads with a die set and you should be good.
 

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2008 gmc envoy_denali
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75 Posts
Discussion Starter #3 (Edited)
Bolt heads are broken off on the manifolds. They've been like this for while, I didn't do it... Manifolds need to come off to get the bolts out. Good chance the manifolds are warped as well. If I have to take everything apart AND by new manifolds I will do long tube headers for an upgrade.
Thinking going with the Patriot brand (painted) and sending them to Jet Hot to get coated...
Mark
 

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2006 chevy trailblazer_lt_ext
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197 Posts
Bolts broken in the head casting huh? Those are fun. MIG a nut on is about the only option due to accessability.
 

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2008 gmc envoy_denali
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75 Posts
Discussion Starter #5
Yup, that's the plan. Won't be fun but it'll need to be done. I am looking into headers and a Y. Does anyone know what the difference is between the '05 & '06 5.3 engines as far as the headers are concerned? The only difference I see is the '05's have the hook up for the EGR on one side. Am I correct?
Mark
 

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2008 gmc envoy_denali
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Discussion Starter #6
https://www.ebay.com/itm/192509162448Taking a bit of a leap here.
LT's, Y, clamps, gaskets and bolts... $220 bucks for the whole kit, I had to give it a try.
I will get them test fit and, if there are no issues , I will send the package out to JetHot for coating. I also picked up a pair of Hi-Flo cats off Amazon. $88 dollars for both. I will have to add the downstream O2 bung though. I am also looking at this cam from PCM of NC.PCM of NC Rob Style Jr Cam 217/221, .60x/.560x, @ .050?, 112 LSA ? PCM of NC, Inc. That, with a nice tune and a trans reprogram should make this truck scoot pretty good...Any thoughts? Any input on cam selection?
Thanks guys
Mark
 

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2008 gmc envoy_denali
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75 Posts
Discussion Starter #9
Just an update. I did a little port work on the headers to clean up some tall weld beads and shipped them off to JetHot. They should have them today. I'll get pics when they come back.
Mark
 

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2008 gmc envoy_denali
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Discussion Starter #10
Cleaned up a few boogerie welds in the exhaust ports and straightened some bent areas on the collectors before sending these to JetHot.
Before.

After.

There were a couple of these tall welds on each header. They cleaned up great.

Both collectors had "shipping issues" as well. When they are shipped in a big box and not very well packed... This is what happens.


I straightened them up as best I could.


All wrapped up and ready to go.
 

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2008 gmc envoy_denali
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Discussion Starter #11
Got them back yesterday and they look great!
JetHot's shipping people know how to pack these right...

You wouldn't think these were the same pipes I shipped out a week and a half ago...



The nice thing is these will last for a long time. I had a set done for my '95 in 2001 and they are still in excellent shape!
Thanks for looking.
Mark
 
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