Abandoned, 2007 Envoy 4.2 Turbo Build

Traz

Well-Known Member
So after much thought and conversation with my fellow Roush employees, I have decided to enhance my envoy with a turbo charger. One of the guys here is something of a wizard with turbos, he's done one for the V8 now the next challenge is mine.

So far we have the turbo we will be using, a somewhat extensive parts list, and the beginnings of a layout for a custom intake, exhaust, and manifold for the Turbo.

No doubt it will be challenging but with the resources at hand, it will get done.

That being said, if there are any opinions on anything feel free to let me know. Parts, brands, tuning, anything, all advice is appreciated.

I'll do my best to keep it updated, although this won't pick up speed for another month or so.. Thanks
 

Capote

Platinum Supporter
I'll be watching this thread anxiously :cool:
What Turbo did you choose? I've got a GT37, going for a Rear Mount setup.
 
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Traz

Traz

Well-Known Member
HX35W for the 98-01 Cummins.

Everything else is laid out on paper and my drawing skills are lacking XD but we have a custom intake, and setup for the Turbo up front with the engine. Also included when the time comes are as many pics as possible of tear down, rebuild, and the custom work for everything
 

Capote

Platinum Supporter
Must be nice to have some Rousch brains helping you out. Just me and two other people in a small garage. But we've done some sweet stuff in there lol. How much boost are you planning to run?
 

Reprise

Lifetime VIP Supporter
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Traz

Traz

Well-Known Member
Oh yeah it's awesome.
I was told that the stock engine can hold up to 7-8, but then someone told me its more like 10-15. I figure with forged internals and shut like that I'm wanting between 8-10
 
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Traz

Traz

Well-Known Member
Really the primary goal is 400+hp. The few turbo envoys that I have seen have gone a bit above that. But I'll be happy with anything above 375
 

Capote

Platinum Supporter
Oh yeah it's awesome.
I was told that the stock engine can hold up to 7-8, but then someone told me its more like 10-15. I figure with forged internals and shut like that I'm wanting between 8-10
It is confirmed to handle 17Ibs stock. I'm aiming for 400+ as well. So you're gonna have some forged internals made up? I'm not going down that path, only due to how expensive it is, since nobody makes anything aftermarket for this engine (internally) unless requested by someone. It seems that these engines can handle mild boost without any issue anyway. Only time i'd ramp it up is when bringing it up to the strip. So perhaps once a month, when race season starts back up?
 
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Traz

Traz

Well-Known Member
See forged internals are definitely an interest. But looking at the cost it gets a bit ridiculous. Definitely new seals and gaskets, new intake and exhaust valves, springs etc.

Also a racing torque converter, servo and shift kits, new suspension, brakes, steering gear, spark, fuel systems ETc. Albeit my Envoy is an 07 and I just hit 81k miles, Im still going to swap in new stuff. And some custom head bolts to keep everything nice and tight. My first priority is the suspension, steering, brakes. Then by the time that's done hopefully the custom work will be under way
 

Capote

Platinum Supporter
See forged internals are definitely an interest. But looking at the cost it gets a bit ridiculous. Definitely new seals and gaskets, new intake and exhaust valves, springs etc.
Same here on parts & seals on my end. Melling, Mahle/Clevite & GM parts. :yes:
I do plan on doing another transmission rebuild. My current one will probably take a beating after the Turbo, even though it's got a bunch of goodies, vette servos, deep pan, etc., and an auxiliary cooler. I'll make it pretty much bulletproof this time. 5-pinion planetaries, etc. As far as head bolts, I've read up it's best to use OEM ones with this engine. What're your thoughts on this?
 
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Traz

Traz

Well-Known Member
That's what I've heard too. One of my buddies has the V8 envoy and had a custom set and he swears by them. A friend of his owns a custom shop I believe, 150$ and he spends a weekend hand crafting each one.

I was curious about swapping in a 5 speed manual or automatic because I feel the 4L60E is a little... Underwhelming. However that hasn't lead anywhere that I could find yet

I've noticed some tunes have "helped" but TransGo makes a shift kit, and you can order corvette servos for 1-2 2-3, and I've heard that makes a hell of a difference but a little nervous to try it.

What's the point of upgrading to that much power if I can't get it to the wheels
 

Capote

Platinum Supporter
I'm just gonna stick to OEM head bolts, GM upgraded the bolt as the years went on (and others like Fel-Pro followed suite). I think the 4L60e is a great transmission, a lot of aftermarket options and people running them. Yeah I've got the TransGo kit and pinless accumulators. The Vette servos make the shifts nice and firm, my tune also has the shift pressure bumped up as well. They have a manual valve-body for the 4L60e, but I don't see the point. in converting it and then using a ratchet shifter. You could always upgrade to a 4L80e if you want a beefier transmission Traz.
 

Mooseman

Moderator
And don't forget the rear diff. The stock 8.0 in the shorties have trouble surviving behind the stock 4.2 and a little abuse. At the very least, you'll have to upgrade at least to the 8.6 from an EXT or V8 truck with the rear ABS sensors (06+). If you want truly bullet proof, you would have to source out an SS 9.5.
 

Sparky

Moderator
I think the weakest part in the 8.6 would be the G80 if it has one as they don't like abuse. If you go with the 8.6, get a different, stronger carrier.
 
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Traz

Traz

Well-Known Member
I was looking into the SS diff. Can you buy aftermarket assemblies? We have plenty of spares here in Michigan but not loving the idea of putting a diff with 150k+ miles into a vehicle that has 81k. Just me though.

I'll try out the head bolts and let you know what I think. Did you install the trans kit and servo yourself? I've heard the process is pretty easy and doesn't take long but I've never tried it.

I don't hate the trans, if the shifting was firm and to the point it would be nice.

My biggest issue is when I'm getting on the highway and I put my foot down, the engine says LETS GO MATE! and the trans says "well hold on let's think abOUT LETS GO TOO!!!
 

Sparky

Moderator
Between a shift kit and updated programming the trans could respond very quickly too. I just wonder about long-term longevity of it.

There are aftermarket parts available for both the 8.6 10 bolt and the 14 bolt from the SS. Not sure about the axle shafts (though I think Moser will make axle shafts for just about anything?), but the carriers, gears, etc yes there's stuff for.
 
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Traz

Traz

Well-Known Member
I would hope as long as I'm not trying to gun it all the time (which I'm not) that it would hold up for a decent amount of time.

Thanks I appreciate that I'll definitely look into it.

Side note: I absolutely love the 4.2, I honestly don't think people give it enough credit. Nice power, smooth, it's an absolute joy
 

HARDTRAILZ

Moderator
Get a 9.5 from an SS for sure. Everything is available aftermarket so just buy one cheap and swap in the upgrades the SS guys do.

I dumped the stock g86 carrier and did an open with a lunchbox locker for my offroad use, but you may want to source a better traction aid for your needs.
 

HARDTRAILZ

Moderator
The G86 prolly would be decent for you. Otherwise a Truetrac or Eaton Posi would be what I would look at.
 
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Traz

Traz

Well-Known Member
No I hadn't, I didn't know that either XD
I wasn't dead set on the HX35, it was just the one I liked the most. And with a price of 250$ It was a nice deal too.

I'll check out the 40 though, definitely don't want anything giving up on me when I'm goin
 
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Traz

Traz

Well-Known Member
Update: Going with the HX35, one of my fab friends is starting mock up of my custom intake, tax return has been sent and approved, ordered an exhaust manifold to start work on the turbo mount, started sketching the layout of everything from the custom fuel pump, all the way up to mounts and manifolds. Time consuming stuff XD
 

Capote

Platinum Supporter
Update: Going with the HX35, one of my fab friends is starting mock up of my custom intake, tax return has been sent and approved, ordered an exhaust manifold to start work on the turbo mount, started sketching the layout of everything from the custom fuel pump, all the way up to mounts and manifolds. Time consuming stuff XD
Any reason you're not using the stock fuel pump? Just curious. Being that your HX35 has a T4 flange, you could go with one of Jeremy's Turbo up-pipes on Lime-swap.com that are ready to mount to the stock manifold.
http://www.lime-swap.com/products
 
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Traz

Traz

Well-Known Member
It's going bad now so it's just a matter of timing, figure I'll get something nice. My friend has the V8 envoy and swapped in a larger tank from the Sierra (after some modifications) so I hope to do that too. Really? I didn't know that was out there. Seeing as there doesn't look to be a lot of aftermarket support I just figured I'd have to do everything custom.

It's always nice to look at something and say yeah that's one of a kind, however.. Money dictates everything XD
 
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Traz

Traz

Well-Known Member
Any reason you're not using the stock fuel pump? Just curious. Being that your HX35 has a T4 flange, you could go with one of Jeremy's Turbo up-pipes on Lime-swap.com that are ready to mount to the stock manifold.
http://www.lime-swap.com/products
Just looked at the link, that's awesome! Especially the injectors, I was worried I'd have to investigate and find the perfect fit from something else, then buy adapters and that mess but that's awesome. The pipe is a bit on the expensive side but hell, I'm up to 1800$ already, what's 375$? Thanks for the heads up. You guys are the best!:loveintheair:
 

Capote

Platinum Supporter
Just looked at the link, that's awesome! Especially the injectors, I was worried I'd have to investigate and find the perfect fit from something else, then buy adapters and that mess but that's awesome. The pipe is a bit on the expensive side but hell, I'm up to 1800$ already, what's 375$? Thanks for the heads up. You guys are the best!:loveintheair:
Glad to help, I've got the fuel injector harness already. Amazon has 60lb & 80lb Siemen Deka's for the cheapest prices from my searching. Haven't bought those yet. Yeah pricey just for an up-pipe, but its a perfect fit and positioned just right. Plus the money goes to Jeremy, who's been quite a help to a lot of us here over the years.
I have quite a lot of parts bookmarked, so I might have some more things to share with ya bud.

Ohh and just to add, are you using a 2008/2009 exhaust manifold? GM improved the design and exhaust flow with that redesign. And it won't be as prone to cracking as much as the older design was. You can find it pretty cheap on EBay.
 
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Traz

Traz

Well-Known Member
Yeah the 2009 manifold. Hell yeah I'll take any and all info I can get. I'm just going to buy the pipe.
 

Capote

Platinum Supporter
What plugs are you going to run?
 

Capote

Platinum Supporter
No idea actually..
Okay, thought i'd ask because I haven't looked into that myself either.
Upon researching I learned that for every 75-100hp gained when using forced induction or Methanol/N2O, you need to go down two steps in spark plug temp as well as gap the plugs 0.028"-0.032" for low boost under 15lbs. If there's still a mifire issue or plug blowout, you need to decrease five thousandths at a time until it's resolved.
 
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Traz

Traz

Well-Known Member
Gotcha. Well it's going to be a slow day at work today so I guess I know what I'll be doing XD
 

efi-diy

Member
If you have the head off ..

port the exhaust and intake

Then convert the head to run a 3/4" reach flat gasketed spark plug - there is a much wider variety of heat ranges available. This is easy to do on a bridgeport type mill using a suitable 4 flute end mill.
 
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Traz

Traz

Well-Known Member
Hey everyone, any idea about a better trans that bolts into the i6? Or just have to stick with the 4L60e?
 

Capote

Platinum Supporter
Hey everyone, any idea about a better trans that bolts into the i6? Or just have to stick with the 4L60e?
4l80e, but IMO you can just stick with a 4l60e. You can easily make them bulletproof with aftermarket clutches, forward and rear 4 or 5 pinion planetaries, and all the other goodies you'd add to upgrade any level 4l60e.
This site has a massive inventory of parts and upgrades for the TH350, TH400, 2004R, 700R4, 4L60E, and 4L80E.
https://www.700r4l60e.com/store/home.php
 
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Traz

Traz

Well-Known Member
Thanks! You've been a major help with this and the work hasn't even started XD I appreciate it
 

Capote

Platinum Supporter
Thanks! You've been a major help with this and the work hasn't even started XD I appreciate it
No problemo, I like to help out others as much as I can on the forum. I've learned a lot of things here over the years and from hours of researching into various things on the net. I'm especially interested in your build because i'm on the same path.
 
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Traz

Traz

Well-Known Member
How's it going so far? I followed Conekiller on YouTube, exchanged some emails and got ideas from how he worked his. But man it's still a challenge. I'm super picky about trying to find every way to do something, reviewing it a bunch of times and trying to find the best way. And that's for every little thing. It's great to have the money but I feel it's better to plan out every detail that you can before I spend a cent
 

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