2008 GMC Envoy Denali

[n8in8or]

Well I guess getting old is well.... Turns out it might have been the Barra engine I was reading about

I saw something recently….I think it was Hot Rod? They wanted to build a Barra because the Aussies said it could stand up to any engine out there. They couldn’t get their hands on one so instead they built another 4-ish liter, overhead cam, inline 6…..they built the 4.2 that comes in the GMT360 (Trailblazer, Envoy, etc). They built two of them. I’m having trouble remembering now, one was turbo for sure and I think the other was NA? Or maybe one was cheap turbo and the other was more sorted, can’t recall for sure. They only got to run the lower end one and I think they got 400hp and 400tq out of it at the crank. The other one was locked up before they got it on the dyno so they couldn’t run it for that episode. Not sure if they’ve tried running it again or not. Cool story, I know. I with you on the memory thing….

 

[ak diesel driver]

The 3.6 I just rebuilt is called an Alloytech over there. Reminded me of a baby ls like the Corvette uses

 

[n8in8or]

I was going to wait until I really started working on this before I started posting, but I decided it would become tricky to go backwards to find what I've done so far and it made sense to instead lay the foundation for the next phase now and post as small things happen.

I had always had in the back of my mind that when I got the itch for some more power out of this thing that I would build myself a turbo kit. One day this year I was giving it some thought and came to the conclusion that a turbo kit wouldn't be the best power-adder solution for this truck. Since I daily drive this, and take it on trips, I didn't like the idea of all of that heat under the hood, the cramped engine bay for doing repairs and how the kit would get exposed to winter weather/roads. I reasoned instead that a supercharger made more sense, and an LSA supercharger would be right up my alley as I could gather the parts for that over time and it's a nicely packaged unit. So I started doing research - there's a lot more to it than I realized, but still certainly achievable.

The biggest challenge I've found is figuring out the belt drive. There are kits you can buy, some cheap and some quite spendy. The cheap kits run the supercharger off the same belt as all of the accessories. I have read many success stories from people using these kits, so I think they work fine if you get a good one, but there are some limitations: in order to change your boost, you have to change the pulley size on the supercharger, which isn't a big deal, but you can only go so small on that pulley before you start having belt slippage issues. The other way to increase boost is to install an oversize harmonic balancer - this is costly and there's only so big you can go before you have clearance issues. The other thing I don't like about this route is that you're adding more stress to your accessories by having all of that drive tension in the belt that the supercharger adds. While this can be a workable, and relatively cheap solution if planned correctly, I don't love how much it costs to upgrade in the future and the potential stress on the other accessories over time, so I'm going a different route. I'm going to do a belt drive more like the factory CTS-V and ZL1 where the supercharger is driven off of its own belt. To accomplish that, I need to change the accessory drive belt system so it's on what they call "Corvette spacing" - the accessories for Corvettes are further back than truck accessories are, therefore allowing the 2 belt system. The alternator and power steering are pretty easy to figure out because all you need to do is get a bracket for the driver side of the engine to run the alternator and power steering pump and then change at least the power steering pump. The air conditioning is more tricky. Because of where the AC compressor is (low on the passenger side), there are some clearance issues to contend with. For the GMT360 chassis, an easy solution is to buy a bracket that Holley makes and switch over to a Sanden SD7 compressor. This gets a little pricey and I don't love the idea of changing to a different style of AC compressor on this vehicle. I THINK I adapt the original AC compressor so it runs on the same belt as the alternator and power steering instead of the dedicated 4-rib belt the way the factory does, but only time will tell if I'm right.

So here are some pics of the things I have collected so far.

First thing I grabbed for the swap was a set of rectangle port heads. You can get adapter plates to adapt the LSA's rectangle ports to cathedral port heads, but I wanted to change the heads at the same time because it would be an upgrade and it would keep the supercharger lower, helping to avoid possible cowl clearance issues. I also want to add a lid spacer in the future, so this will give me more clearance for that as well. I was lucky enough to stumble on a truck 6.2 that was already pulled and on the ground at the local yard so it was easy to zip the heads off of it. $50 each and they were mine. Score!



Then a few weeks later, an LSA supercharger popped up on Marketplace in my town for $600! I couldn't believe it! Most have been 3 hours away and $1200-ish. I made plans to meet with the guy first thing the next morning and it was mine. It felt so great to have this in my possession! One of the hard parts to get at a good deal was off the list.



Then a few weeks after that, I found a great deal on a CTS-V lid (which is the one I wanted, not the ZL1 lid) that had the intercooler brick already reinforced. Another part that was hard to find at a good deal in my possession!!



I decided since things were starting to get more serious, that I needed an LS short block for mockup purposes. There wasn't anything cheap on Marketplace so I roamed the jumkyard. I found a 6.0 in a van that someone had removed the heads off of so it was crusty.......it also had a grenaded piston. I got that and the 4L80 that was attached to it for $150. The trans will show up in another thread soon....



I found a decent deal on a water pump that was removed from a wrecked G8 GT (same belt spacing as a Corvette) with the belt tensioner already installed, so I snagged that up. It's good enough for mockup purposes at the very least and I could probably install it and be ok, but I'll probably play it safe and just buy a new water pump at the time of installation.



I have 2 AC compressors off of GMT360s, one from a 5.3 (4-rib belt) and one from a 4.2 (6-rib belt). I think swapping the 6-rib pulley to the 5.3 compressor is going to get me pretty close to having this line up with the other accessories, but I won't know until I get things mocked up.



This side project has been a bit of a distraction from other projects, but the prospect of more power and speed is just too sexy to ignore. More to come as I make progress/gather more parts.

 

[smokymtn65]

Nate, have a work colleague that may have 2 new water pumps and no car. Lol he will send me some pics of the items to verify p/n and manufacturer. I will send when i get it.

 

[n8in8or]

Nate, have a work colleague that may have 2 new water pumps and no car. Lol he will send me some pics of the items to verify p/n and manufacturer. I will send when i get it.

Thanks!

 

[n8in8or]

I got some new summer wheels and tires for the Envoy. I’ve been wanting a set of these for about 3 years and I found a set 2 hours away with tires and TPMS sensors already installed for less than half the price of new. These are a copy of GMC “Y-spokes” in a 20” x 9” size, that have the 6” x 5” bolt pattern of the GMT360. The tires are 275/45/20, which is the same OD as the stock 245/60/18, but with more tread width. I need to lower the rear of the truck about an inch to get the overall stance better. In the future I’m planning to get 295/45/20 tires so there will be a little more rubber to fill the wheelwells plus gain some additional tread width. I went for a quick drive after installing them and they ride nice and smooth. I’m happy.

 

[n8in8or]

This is for sale now for $8800. New wheels aren’t included because I sold those to my brother.

 

[n8in8or]

Sold it today. The new owner loves it, so that makes me happy.

 

[Will L.]

Nice to know the next person will enjoy your extra efforts that went into something.

 

[Husker6.5]

So, Nate, next "project" a diesel Escalade?

 

[n8in8or]

So, Nate, next "project" a diesel Escalade?