Maximizing 4.2 performance

smitty5150

Original poster
Member
Nov 18, 2011
1,069
The 4.2l has some potential, even with the limitations caused by our engine management systems. Ported heads, throttle bodies, e fans, exhaust, tunes, etc can all be done to help get the most from our motor. I thought this was a discussion that would be brought up sooner or later, so why not sooner?

I'm considering doing some of the above mentioned upgrades this spring. Well, either that or swapping in a 5.3. Let discuss what you have done, considered doing, or decided to stay away from. How have they benefited you, if at all?
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
Having the catback exhaust, the green filter and opened up stock box, plus the pcmforless tune really helped mine out and has let me maintain what seems to be better mpg than most lifted ones.
 
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smitty5150

Original poster
Member
Nov 18, 2011
1,069
I agree, my catback and intake did help a little. Still running stock tune, that will change when everything else gets sorted.

I am thinking along the lines of picking up an 06 head to part, a throttle body to port, as well as some porting on the exhaust side. Trans will get a shift kit. Thinking about converting to 2wd to kill the t-case loss, as well as an ss rear. Getting an off-road/foul weather truck from uncle Sam(not BOTIESS), so I can afford to go 2 wheel and experiment with adders. There's also the possibility of finding a low mile 5.3/harness/Pcm and doing a swap. All depends on cost vs benefit at this point. By benefit, I mean seat-o-pants meter.
 

07Blazerman

Member
Dec 4, 2011
102
pcmforless tune and supersparkz-which turned out to be a great investment-much smoother idle.
 

STLtrailbSS

Member
Dec 4, 2011
1,617
Swapping a 5.3 if your seriously considering I think over time if your going to put more in gradually after the swap is going to give you the best gain. The 5.3 just has more capability that vortec is more like an LS set up then the 4.2. Imo the 5.3 stock is a gain from a 4.2 but also if you then decide to take that further your going to get better gains from the mods on the 5.3 huge sleeper potential in the 5.3 that would be pretty mean.
 

ScarabEpic22

Member
Nov 20, 2011
728
If you wanna do a 5.3 swap, hit me up for how to run the PCM setup. Its a LOT easier than we all initially thought, remember the 03-04 LWB trucks came with 5.3s...run a 1MB LS1B PCM, flash the correct OS (a 5.3 TB OS), and do the wiring to match that of a LWB truck. Retain ALL creature comforts plus get a 5.3 (or whatever V8 you wanna throw at it, just adjust the PCM correctly. 4.8, 5.3, 6.0, 6.2, even a 7.0L ... :biggrin: [6.2, 7.0L need a converter box]).

For the 02-05 I6s, buy an 06-07 head (not 08-09 unless you wanna swap cams, defeats the purpose) and port it. If you wanna drop serious $$$, a custom set of cams is in order. Cams + ported head should be good for at least 50hp (plus a retune). Toss efans, intake, exhaust, and the 220rhwp I6 is probably close to 300rwhp.

But if you do a V8 swap, you can drop pretty much any power adder (Maggie, ProCharger, turbo, etc) in as well.
 

07Blazerman

Member
Dec 4, 2011
102
Steve A said:
I ordered my tune, and thanks for turning me onto the Supersparkz. I just read the entire thread about them and I am going to order them tomorrow as soon as my paycheck hits the bank.

Thank you.

Steve

You order those and I will order the filter.:wootwoot:
 

07Blazerman

Member
Dec 4, 2011
102
1st mod K&N drop in filter-performance gain=0 and later sold
2nd mod custom catback with flowmaster muffler-performance gain=very little outside of sound and later removed
3rd mod K&N CAI kit-performance gain=very little outside of sound and 1/2 mpg mixed driving and thats being generous and later sold
4th mod Jet mass air sensor-performance gain=0 and later sold
5th mod throttle body spacer-performance gain=0 but sound increased
6th mod removing the Jet mass air sensor and adding the Pcmforless premium tune-performance gain=best mod to date and over 1 mpg gained
7th mod intake resonator delete (Vortec 4200 box)-performance gain=0 but increase in sound
8th mod removing the K&N CAI and resonator delete and going back to stock intake and going with the Walker Quietflow exhaust cat back-performance lost negligible
9th mod Supersparkz-performance gain negligible, idle quality increased and easier starts, mpg not really any-second best mod performed
10th mod Pcmforless retune to remove options of catback and intake and also went with the 87 octane tune-gas is killing me
11th mod possibly Amsoil drop in filter just for better filtration than the Ac Delco paper in their now
12th mod possibly the ported throttle body from Supermodulation, but waiting to see if Pittdawg has his idle issues solved
No major engine work ie head ported or cams in the near future-getting a house instead, so that is my list and what my opinions are on the various mods.:twocents:
 

ieatglue

Member
Nov 20, 2011
152
Quite honestly, just proper maintenance would be the best you could do. If you want more power, trade it in for an SS :raspberry:
 

Shdwdrgn

Member
Dec 4, 2011
568
I hope someone does a how-to thread on head porting. This was easy back in the day with my 74 Pontiac - just pull the intake and use the carbon as a guideline for the mis-matched areas. Can you still do this by hand, or does it require some kind of fancy machinery these days?

Some questions about porting the heads...
  • What's the expected HP increase with just the ported heads?
  • Does the HP increase come at the cost of mpg?
  • Why are the 06-07 heads recommended?
  • What needs to be adjusted in the tune? Does the pcm4less tune account for the differences, and if not, do they have the right tables to make this change?
  • Anyone have a rough breakdown of costs?
 

Jkust

Member
Dec 4, 2011
946
Agree with the above. You are 10 years old now. Off load it and upgrade to something with a 5.3 if you like to mod. It is easily modable to more hp and tq than the SS with off the shelf parts. The 5.3 given how common they are in trucks just scream to be modded. Even stock, you will be suprised at the performance increase over a 4.2 even a modded 4.2.
 

06Envoy

Member
Dec 4, 2011
419
Jkust said:
Even stock, you will be suprised at the performance increase over a 4.2 even a modded 4.2.
Ah, hold on there tiger...
Please read THIS THREAD from the OS.

The short version of that thread is that when I raced 0-100kph(0-60mph) my stock 5.3l vs my modded 4.2l the race was much closer than I expected it to be. Nose of 4.2 to Tail of 5.3 every time.
For those who like to keep all things equal, here are the stats of each truck based on RPO codes.
Both have the G80 rear end.
Both are EXT/XL.
Both have 3.42 gears.
Both are 4x4.
Both running stock sized tires/rims. (17")
We swapped out drivers.
Multiple runs in both directions of the divided highway.

Now that being said, I'm getting closer to rerunning that race. Since then, I've added a K&N CAI and a tune to my 5.3. Now I'm expecting to kick my wife's butt!
So I don't have to listen to her 'Why did you buy a v8? It's the same as my V6." I don't even try to tell her it's not a v6...:rotfl:


But I agree with everything else you mentioned. Sell off the older truck and get into a newer one if you can. The 5.3 is easier to mod than the 4.2.

As for trying to stay ontopic, I'm going to try those Supersparkz on my wife's TB. Can't hurt and it's a cheap mod.
 

Jkust

Member
Dec 4, 2011
946
06Envoy said:
Ah, hold on there tiger...
Please read THIS THREAD from the OS.

The short version of that thread is that when I raced 0-100kph(0-60mph) my stock 5.3l vs my modded 4.2l the race was much closer than I expected it to be. Nose of 4.2 to Tail of 5.3 every time.
For those who like to keep all things equal, here are the stats of each truck based on RPO codes.
Both have the G80 rear end.
Both are EXT/XL.
Both have 3.42 gears.
Both are 4x4.
Both running stock sized tires/rims. (17")
We swapped out drivers.
Multiple runs in both directions of the divided highway.

Now that being said, I'm getting closer to rerunning that race. Since then, I've added a K&N CAI and a tune to my 5.3. Now I'm expecting to kick my wife's butt!
So I don't have to listen to her 'Why did you buy a v8? It's the same as my V6." I don't even try to tell her it's not a v6...:rotfl:


But I agree with everything else you mentioned. Sell off the older truck and get into a newer one if you can. The 5.3 is easier to mod than the 4.2.

As for trying to stay ontopic, I'm going to try those Supersparkz on my wife's TB. Can't hurt and it's a cheap mod.

Ok now hook my boat up to each and let's try it again. Then lets take the 5.3 modded, a 4.2 modded and try it all over. We'll add a supercharger to each then add up how much it cost in time and money to add it. I don't care much about 0 - 60 but 0-to 60 with a heavy trailer I do. I could come up with iterations all day as to why 2 extra cylinders is going to be or can be made to be higher performing.

I do want to hear how your 5.3 runs out with the tune.
 

smitty5150

Original poster
Member
Nov 18, 2011
1,069
As far as trading is concerned, no thanks. I am mailing my last payment this month and will enjoy the freedom associated with outright ownership. I already have Intake and exhaust. I think I am going to do e fans, tune definitely, and a shift it for the trans. As far as porting an 06+ head, or any spare head, deciding against that one. It'll easily run me over $2000 to do a ported head, tb, and stainlessworks exhaust. For that price I could start working on a v8 swap in an s10. Better yet, an older full size that already has a v8 and just mod the shit out of it.
 

zyvoy

Member
Feb 6, 2014
1
ScarabEpic22 said:
If you wanna do a 5.3 swap, hit me up for how to run the PCM setup. Its a LOT easier than we all initially thought, remember the 03-04 LWB trucks came with 5.3s...run a 1MB LS1B PCM, flash the correct OS (a 5.3 TB OS), and do the wiring to match that of a LWB truck. Retain ALL creature comforts plus get a 5.3 (or whatever V8 you wanna throw at it, just adjust the PCM correctly. 4.8, 5.3, 6.0, 6.2, even a 7.0L ... :biggrin: [6.2, 7.0L need a converter box]).

For the 02-05 I6s, buy an 06-07 head (not 08-09 unless you wanna swap cams, defeats the purpose) and port it. If you wanna drop serious $$$, a custom set of cams is in order. Cams + ported head should be good for at least 50hp (plus a retune). Toss efans, intake, exhaust, and the 220rhwp I6 is probably close to 300rwhp.

But if you do a V8 swap, you can drop pretty much any power adder (Maggie, ProCharger, turbo, etc) in as well.



I have a 2002 Envoy SLT (4.2 Inline 6) and I was wondering what the process would be to drop a V8 (Probably a 5.3) in it? Any help would be appreciated. Thanks
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
zyvoy said:
I have a 2002 Envoy SLT (4.2 Inline 6) and I was wondering what the process would be to drop a V8 (Probably a 5.3) in it? Any help would be appreciated. Thanks

Best and cheapest option is a different truck with a v8 stock. In all honesty, it is not worth swapping one in when the 5.3 and 6.0 can be had stock.
 

xj2202009

Member
Mar 27, 2012
105
When I had the transmission rebuild, the shop did a servo upgrade and that made significant difference best felt when towing.
 

bobdec

Member
Apr 19, 2013
233
smitty, you may get some ideas over here ' vortec4200.com • Index page ' also as far as tuning a customized setup this place is Vortec specialized Home . I personally would rather build a faster car than buy one so I understand your question.

Question in post #11 , why 06-07 heads .. The 06-07 4200 heads had larger cams and valves, HP was up to 291 they also used MAF fueling above 3600 RPM.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
More than one mod was just forced to clean up some off-topic and divisive posts. We hate to do that, but this isn't the kind of forum that goes down that path. :frown:

Please keep GMTN at least ten times as collegial as congress, willya guys?

Thanks. :thumbsup:
 

Mike534x

Member
Apr 9, 2012
994
Was the EXT the only one with the 5.3? All the ones I've seen for sale were 4.2's. Can't find one with a 5.3.

5.3's are rare hence the reason why you see so many 4.2's. The 5.3 was offered in the SWB Envoy Denali 05-09, and 03-06 in the EXT only. 06+ SWB Trailblazer models received the optional package to get the 5.3.

One downside to the 5.3 is the lack of documentation, the info available is nowhere near as plentiful as the 4.2.... well when pertaining to this platform. Thankfully the LH6 they used is pretty much an LS engine so most guides and such are at least applicable to it.
 

Capote

Supporting Donor
Member
Jul 14, 2014
24,227
Atlanta, GA

Capote

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