Cam shaft

Traz

Original poster
Jan 10, 2018
134
Michigan
Rebuilding envoy and slapping a turbo on it. First things first is new parts. Trying to find a performance camshaft that will work with my 4.2l. Any ideas? Not sure where to start looking. Thanks
 

Reprise

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I have the 5.3L in my Envoy, but (I think) I know a little bit about the 4.2L...here goes...

The 4.2L LL8 is a DOHC engine. To top it off, the exhaust cam is hydro-mechanically variable. That's one big reason why the motor has good power throughout its entire RPM range, down low and up high. It's damn near the equal of the optional 5.3L (which has a wee bit more TQ, mainly benefiting those who tow.) I have a lot of respect for the 4.2L as a result.

If you could find someone to make a custom grind for you, get ready to open your wallet.
I think Texas Speed and Performance (www.texas-speed.com) might be a good resource to check with.
PCM of NC (also one of our vendors) offers some packages for the 360s - but none include a cam upgrade.

Besides the cams, you'd need to adjust fuel / spark tables, so you're looking at dyno time, trial & error tunes...see where this would be going?

There are people here that have / are adding turbos to their 4.2L - at least one that I know of was running a ton of boost (it spends time at the strip). They may have some suggestions for you. Check the forum list for the right area to find them in. I know @Capote is just starting off a turbo project, btw.

Outside of turbos, there's not a lot of aftermarket support for the LL8 - as good as it was, the engine was orphaned when the 360 platform was retired (being an inline six, its applications were limited, mainly due to size constraints.) The Lambda platform that replaced the 360s is FF, as well.

The engine would fit in the full-size pickups & SUVs - but they already have good motors. Since the 4.2L is a bit thirsty (there's only 1-2 mpg difference between it and the optional 5.3L), it doesn't make sense to retrofit it in a Silverado, Tahoe, or Burb.

Depending on how serious you are about hopping up your Voy - you might be better to replace it with a Denali (5.3L standard) or a TBSS (6.0 LS2 plus 4.10 gear plus AWD). Both are available in the shorter wheelbase (SWB).

There's plenty of aftermarket support for the LSx engines. But transplanting a V8 into your current truck is more trouble than it's worth (it's been discussed several times). Easier / cheaper to get another truck, IMO.
 
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Traz

Original poster
Jan 10, 2018
134
Michigan
I see where you're going. I work at roush and have access to their equipment. One of the guys I'm working with is a wizard with turbos so we already knew about the fuel/spark etc. Thanks for being honest and to the point though. A more aggressive camshaft was talked about, but if the one already installed is pushing the limits of what it can do then there is nothing I can do about that.

There's a lot that going into making the 4.2 able to co-exsist with the turbo. It was more of a question of seeing anything else that could be added.

Anyway, thanks
 

Reprise

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No problem at all. Like I mentioned...there are people here who've done what you're about to undertake. Feel free to stick around and gather some info, have a laugh or two, etc. And we'd love to read about your progress / results, too.

Nice gig you've got there at Roush :thumbsup:
 

Traz

Original poster
Jan 10, 2018
134
Michigan
Oh yeah it's good stuff. Right now it's a lot of research and planning before I even attempt to start the build. (also waiting for that tax return lol) I'll be sure to keep everyone updated. Thanks again!
 

littleblazer

Member
Jul 6, 2014
9,265
I believe there was talks of some blanks being available. They were made by extending the 5 or 4 cylinder atlas blanks. Not cheap and I don't think they're around anymore. Texas speed or comp would be the ones I'd ask. Heck even gm performance maybe. They did have a old trophy truck or similar with the 6 cylinder iirc. Maybe they could point you in a direction...
 

Traz

Original poster
Jan 10, 2018
134
Michigan
I believe there was talks of some blanks being available. They were made by extending the 5 or 4 cylinder atlas blanks. Not cheap and I don't think they're around anymore. Texas speed or comp would be the ones I'd ask. Heck even gm performance maybe. They did have a old trophy truck or similar with the 6 cylinder iirc. Maybe they could point you in a direction...

Thanks I appreciate it a lot I'll keep an eye out and see if I can find something
 

Capote

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Jul 14, 2014
24,227
Atlanta, GA
@Traz

Over at Vortec4200.com there has been a lot of 4200 Turbo builds over the years, but almost none done in a GMT360. One in particular laid the old "A factory Atlas LL8 can't handle more than 7Ibs of boost" myth to rest, view the build here: Vortec 4200 Turbo engine swap into an IROC Z. At one point he had it running 17Ibs of boost at the strip IIRC.

I suggest you visit the site, it has a lot of info to offer when planning your build. But you're not gonna be able to sign up and start posting anything there. The admins are AWOL. @limequat and some members there are considering starting a newer forum. @limequat is also the man to go to with questions, being that he was a part of that Turbo 4200 IROC Z project.

I haven't started any psychical aspects of the build yet, just collecting parts I need (like you, tax return will give me a push lol). Pretty much new internal parts, forged parts, fuel related, '06/'07 PCM, etc. for the donor engine at this phase. I'll be keeping my original motor in my truck and swapping in the refurbished/beefed up motor once it's all done. Then we'll move on to phase two which will be installing & running everything for the Turbo and lots of tuning. I'm hanging on to the original motor, just in case something goes wrong down the road. By the way are you going for a normal Turbo setup or rear mount? And by all means feel free to PM me and keep me up to date on your project, we could probably help each-other out.
 
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Mooseman

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Dec 4, 2011
25,257
Ottawa, ON
@limequat comes around here once in a while. We could start a turbo section under the 4.2 section if there is enough interest (with approvals).
 

Capote

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You know I'm down for that.
 
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Mooseman

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Dec 4, 2011
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We would have to get enough interest in it and have more than two or three threads in there. Dunno if @limequat still does a lot of stuff on the 4.2.
 
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Reprise

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You know I'm down for that.

Same here. I'd even suggest a Forced Induction section, and split it into turbo / supercharger (V8) subforums
(because when I win the lottery, I'll be slapping a blower on the Voy) :tongue:
 
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limequat

Member
Dec 8, 2011
520
I'm still doing the tunes, but gave up on hard parts in the way of cams or turbo stuff.

emtechmotorsports can hook probably hook you up with cam blanks. As was mentioned, be prepared to open your wallet. Marc's prices are fair, but...the cams are long, you need two, and THEN you still have to pay for the grind.

For the money, I don't see the point. How much time do you spend at redline anyway?

Turbos on the otherhand....go with a slightly smaller turbo that matches your stock cam profile, and you'll have all the torque you ever wanted, and you'll never again think about the extra 50 hp you could get at 7000 RPM with custom cams and head port.

That said, if you have the time and the money, there is a lot of power bottled up in the exhaust ports and cams. If somebody wants to be the guinea pig, I'll help develop a tune that would go for the same price as all the other tunes ($99 mail order or $200 road tune).
 

Capote

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I've read up about how much some guys spent on the blanks. Crazy expensive, remember reading on some inline 6 forum that one guy spent $1700 on the pair. I'm not trying to squeeze every ounce of power I can get out of a 4.2, I'm not loaded by any means. Just doing this for the fun of it, for more power in general, and something unique instead of doing a 5.3 swap. @limequat I have a small frame GT37 Turbo.
 
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littleblazer

Member
Jul 6, 2014
9,265
So a really good grind couldn't help total area under the curve on a turbo i6 or is the vvt that good?
 

limequat

Member
Dec 8, 2011
520
^ In my opinion, no. The TB is already setup for low end torque. The tiny exhaust ports and exhaust cam attest to that. Going bigger means gains past the existing torque peak of ~4500 rpm.

The VVT is good though. Try driving for a few days with the VVT solenoid unplugged!
 

littleblazer

Member
Jul 6, 2014
9,265
^ In my opinion, no. The TB is already setup for low end torque. The tiny exhaust ports and exhaust cam attest to that. Going bigger means gains past the existing torque peak of ~4500 rpm.

The VVT is good though. Try driving for a few days with the VVT solenoid unplugged!
See I have never actually looked at a dyno graph of these trucks so I can't really say anything but if the peak is around 4500 I would have to say the torque curve is pretty broad then no? And if that is the case then it would be beneficial to simply increase air flow in the head rather than worry about the cam like was said right? New stuff is foreign to me. I'm used to redlines in the 5k rpm range with peaks around 3k for torque. :rotfl:
 

Traz

Original poster
Jan 10, 2018
134
Michigan
Thanks for all the info everyone, it's pretty dead at trailvoy so it's awesome to see all the responses in such a short time. If that's the case I'll just stick with the turbo. It'll probably be a month or 2, but I'll keep everything updated as best I can
 
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Capote

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Thanks for all the info everyone, it's pretty dead at trailvoy so it's awesome to see all the responses in such a short time. If that's the case I'll just stick with the turbo. It'll probably be a month or 2, but I'll keep everything updated as best I can
Make a build thread for the Turbo, i'll be doing the same once I get to tearing down the spare motor I have.
 
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07TrailyLS

Member
May 7, 2014
423
Toledo ohio
Very curious to see how these turn out. @Capote and @Traz do you guys plan on getting a good amount of pics for a “how-to” for tearing down and rebuilding the motor? I feel that’s one thing we lack on this site is an actual “how to teardown and rebuild the 4.2” thread
 

Traz

Original poster
Jan 10, 2018
134
Michigan
Very curious to see how these turn out. @Capote and @Traz do you guys plan on getting a good amount of pics for a “how-to” for tearing down and rebuilding the motor? I feel that’s one thing we lack on this site is an actual “how to teardown and rebuild the 4.2” thread
Oh yeah I plan on documenting absolutely everything. Or rather as much as I can. I hate that I can't find enough out there
 
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07TrailyLS

Member
May 7, 2014
423
Toledo ohio
Oh yeah I plan on documenting absolutely everything. Or rather as much as I can. I hate that I can't find enough out there
Great news man! Can’t wait to see all the info. Most of these trucks are 10+ years old. Pretty soon people are going to have to start tearing there motors down at one point or another and they’re going to head here for guidance.
 

djthumper

Administrator
Nov 20, 2011
14,950
North Las Vegas
Thanks for all the info everyone, it's pretty dead at trailvoy so it's awesome to see all the responses in such a short time. If that's the case I'll just stick with the turbo. It'll probably be a month or 2, but I'll keep everything updated as best I can
Trailvoy has been dead since 2011 when most of us left there and came here.
 

07TrailyLS

Member
May 7, 2014
423
Toledo ohio
It’s a shame that trailvoy is the first link on google search for anything trailblazer related. I have a hard time finding ANYTHING from this site on the first page. Is there a way to make searches point toward this page rather the trash page?
 

djthumper

Administrator
Nov 20, 2011
14,950
North Las Vegas
A lot of it is because that site is so established. Some of the articles were moved over here but trailvoy getting the first hits is due to the activity since it shows there first and people go there first. You can narrow things down to this site by adding site:gmtnation.com to the end of your search.
 
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Reprise

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Most of these trucks are 10+ years old. Pretty soon people are going to have to start tearing there motors down at one point or another and they’re going to head here for guidance.

Given the age of the platform, it not being made any longer, the rep that the 360s had, rust issues, etc. - I'm guessing that only the hardcore owners would even consider doing that - and most of them are already here. :biggrin: Depending on the mileage the owner got out of the original, they might grab a JY engine for cheap, and run that while they're rebuilding the original motor, since it lasted so long. Or vice-versa.
IMO, most of the people who show up now as 'new' owners are here b/c they bought the truck cheaply, it's often their only vehicle, and they don't have a ton of $$$ to shotgun it with parts (although many could probably use them!) So they're not 'invested' in the truck, like we are - they'll likely cut their losses and move to another 'beater'.

Trailvoy has been dead since 2011 when most of us left there and came here.

I wonder how much the original owner got paid by the buyer. Hope he made out like a bandit. Meanwhile, the company who bought it probably keeps it up just for the ad revenue (e.g.; 'who cares if the site is dead? We're still making $$$').
There's certainly a bunch of ads every time I access the site b/c (only) something from over there came up in my search results.
 
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Traz

Original poster
Jan 10, 2018
134
Michigan
Hell, mines an 07, 1 owner before me, just hit 81k miles and I paid 8k$ for mine. But it's in beautiful condition, the only reason I'm doing work is because I can XD

2/4

3/4

4/4
 

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limequat

Member
Dec 8, 2011
520
See I have never actually looked at a dyno graph of these trucks so I can't really say anything but if the peak is around 4500 I would have to say the torque curve is pretty broad then no? And if that is the case then it would be beneficial to simply increase air flow in the head rather than worry about the cam like was said right? New stuff is foreign to me. I'm used to redlines in the 5k rpm range with peaks around 3k for torque. :rotfl:

Yes, it is a broad curve! There is certainly power to be had by porting the exhaust ports.
 
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efi-diy

Member
Dec 9, 2011
32
The stock exhaust port flow stalls at 160cfm @28" water pressure. This occurs close to 0.300" exh. valve lift. The exhaust port needs about 5 hours work per hole to get it to flow. This brings the exhaust flow up to 210/230 cfm depending on the the work done.

The intake port has a real bad sharp edge at the end of the short turn. In stock form it stalls @ 220 cfm. Reworking the intake port to remove this edge gains 100 cfm.

These mods should net about 30 hp - more with a high flow exhaust.

Some links to the original 4200 performance group.

stock head

ported head

ported exhaust cast

There are sources to get 1mm OS intake/exhaust valves/seats, performance valve springs/retainers. Good rods/pistons are also available.

The opel chassis dyno'ed @ 425 HP in 2nd gear - we were losing about 25HP - but no choice otherwise we would have over speed the dyno. 4th gear @7400 rpm was good for 208.9 mph on the salt. Go look it up e/gms. They spun the engine as high as 9200 rpm on a few runs - it was a wicked sound that I won't forget - open headers.

A fully prepared turbo'ed 4200 has made 1300HP - 2005 hot rod drag week. That 67 nova wagon went deep into the 8's @ 145 ish mph.

The fundamentals are there - they just need some help.
 
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Reprise

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They spun the engine as high as 9200 rpm on a few runs - it was a wicked sound that I won't forget - open headers.

That's amazing (well, for a GM product, anyway - OHC will rev higher / more efficient over OHV/pushrod).

Such a shame that the 4200 is limited in what it can fit into (from an OEM standpoint.) and that it's a bit thirsty, given current CAFE rules. I know there have been discussions on how the 4200 could otherwise work in the 1/2 ton pickups & the Tahoe / Yukon (as additional options, not as the only offering.)
 

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