GMT900 6.2 PPV Build Log

[swathdiver]

This is good data, you will see further down the timeline soon that it was down on power with the cam before I went and put a turbo on it. BTR estimates something like 60-70bhp with the cam in a 6.2, I expected at least 400whp on the dyno and had a suspicion something was up. It ties in with the blowby I observed.

Stellar idea, don't fear the gear! I've not yet decided what gear ratio I'll settle on when replacing this 3.08, maybe a 4.10? Need to pick between a eaton trutrac or yukon dura-grip too.

The non-ppv wheels that came with the car were on 265-65-18 tires. If I wasn't on these 18s, I don't know if the 4pot brakes would have fit under them. Wheels are on the list however. You mentioned going down the track, what size rear tire have you run? Anything in the 28x12.5 or even 31x12.5 range? Trying to get a grasp for what would fit.

It is a billet 278mm converter, part number 07-09-07-2A. I think with my end goal of 6-700whp its a good addition to the build. Even better it came with the car when I bought it. I am glad that the 6L80 was gone through, rebuilt and some choice upgrades done like this converter and clutches. The horror stories I've read about stock converter/stock tune 6L80s blowing up is a bit scary.

Turbochargers don't like to pull on gears like naturally aspirated cars do. 3.42s or 3.73s at most would be my recommendation.

We run that size tire on my pickup that makes 375 horses. We run Michelin Defenders on both of them.

For those higher horsepower motors, the heavier billet converters are necessary for durability even though they cost a little more horsepower to turn. As for the JMBX, well, we're still running them without issue, half a million miles on 3 trucks so far.

 

[Joseph Garcia]

Very nice build thread, and I wish you the best of outcomes with your modded truck. It is an incredible thrill when you give it the throttle and the truck leaps forward like a bullet in response.

 

[ls3_ppv]

The problems continued with the ebay turbo kit and the tune. First up, I couldn't make more than 2-3psi of boost before the car starting cutting out and falling on its face. We messed with the tune and got it running good enough that I felt I could take it up to Kentucky again for LSfest East this year and have some pros look at it. TTS (The Tuning School) was at the event this year and we signed up for a dyno session to have some instructors go through the tuning process with us and work on getting the PPV to run better.

We have arrived at Beech Bend raceway for LSfest, don't mind the cracked dash.

Got a campground crib too:


And got to see some cool builds:





Unfortunately, the dyno session got cancelled and my hopes of getting a solid tune vanished. We did get the instructors to help fix a couple quick things and give us some pointers on what is needed to scale the MAP sensor properly, verify injector data was loaded correctly and fix this odd long crank startup that happens after each calibration flash. Beggars cant be choosers so itll have to do until I can get a pro to really dial this thing in. We were on the lightest wastegate spring at this point so I could peak maybe 4psi of boost on a crappy ebay wastegate after the MAP was scaled correctly. I took notes, talked to some more people smarter than me at all the vendor booths and made a checklist of things I needed to do.

1. Get a better wastegate
2. Get a better BOV
3. Hire a reputable tuner
4. Swap out the truck MAF for a better resolution LS3 card style MAF sensor

Time to head back home, we got work to do!

 

[ls3_ppv]

Its Thanksgiving 2022 now and we've made some progress on the checklist from LSfest.


Truck style MAF-------------------------------------------------LS3 card style MAF



Also discovered the rubber 90 degree boot coming off the throttle body was sucking in during operation so I took the opportunity here doing the MAF swap to rework this whole intake pipe with an aluminum 90 and the MAF bung welded into the straightest section of pipe here.



Also got the JDM bov installed. Things are looking good.


Also got this amazing shot helping to pickup this c6z from Utah and driving it back home.

 

[ls3_ppv]

Time to tackle the wastegate, this ebay one was coming apart. We are now in April of 2023 and work has been a bear so the PPV got sidelined for a bit until I could address the wastegate and tune.

Dang she thicc! Got me a turbosmart powergate 60mm



chopped off the 38mm wastegate flange, hogged out the hole



Should be zero issues now dumping boost and holding spring pressure with this 60mm. Its nearly as big as the turbo!



Also finally caved in and got a fancy catch can. After talking to the Might Mouse owner at LSfest two years in a row and asking all kinds of questions, I got the gen 5 XL can with -10AN fittings.
Let's call this PPV PCV rev. 4 and final PCV configuration. I love this, it works, its easy to drain and observe oil level and combines everything my rev. 3 setup did into a clean package with additional capacity. I feel likeI've made a string of good decisions to dial this PPV in up to this point now, things are looking pretty good!