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!

 

[ls3_ppv]

Its now July 2023, been driving it for a few months and partying with this little 62mm turbo. It's on spring pressure at about 6-7psi at this point and I am racking up miles as much as I can and saving up my pennies for a regear and trutrac. Unfortunately, I start hearing a tapping noise and dig in to investigate. I got these carnage pics to share, its a major heart break.







Yuppp thats valve contact on that underside of the exhaust valve there, rockers destroyed every single valve tip, there's metal EVERYWHERE!

 

[ls3_ppv]

I was left scratching my head here but had a good idea to reach out to BTR since the pushrods, rocks, springs, retainers are all BTR and maybe they can work through some root cause analysis with me.



What you are looking at is an email from Kyle@BTR telling me that THE Brian Tooley was able to identify that I had 1.8ratio LS7 rockers in these LS3 heads. The second picture is the LS7 rocker on the left sitting next to a stock LS3 rocker on the right. 1.8 ratio rockers no worky in 1.7 ratio heads. Notice the wear pattern on both. WOW!

Well, problem identified. I can fix this but I do not trust this block anymore. It's coming out and getting sent to the machine shop for some work and a rebuild.

Its now October 2023. Assembly after a rehone, crank turned .010 and balanced, block decked .005, ARP rod bolts, new piston rings w/ upgraded steel top ring gapped to .024 and .026. All new bearings. Re-used the camshaft.



Some choice upgrades while its apart. -10AN turbo oil drain bung off the oil pan and another -10AN bunch for the driver side PCV connection.


I have already popped an AC line from being too close to the turbo hotside and extended that line away. I also extended the heater core lines and relocated the passenger side battery ground from the front to the rear of the passenger cylinder head. I was in heat management mode, this stuff sucks to work with and I probably should have wet the fiberglass but under hood temps are down and I haven't had any more issues with lines around the turbo T4 flange. Next time I'd look at cerakote or some high temp paint perhaps.

 

[ls3_ppv]

PPV is back together, running smooth. Guess what, there's no more idle blowby! I have vacuum at the oil fill cap, its no longer sputtering coming to a stop too! I think its time to get something better than an LSfest campground tune on this thing. I reach out to PCM Of NC at a friend's recommendation for some help to start turning the power up and get a remote tune. I didn't have easy access to a dyno session and liked the ability to send logs back and forth a few times to get the tuning dialed in. My buddy's recommendation was great, this shop is easy to work with and very flexible as I've worked through these issues and made various upcoming upgrades.

Its now December 2023, the PPV has some miles and is out of break-in. I stumble across this thread: 9.5SF Swap and source a $120 denali rear end. I decide to rebuild it with all new races, bearings, seals, brake hardware, rotors, pads, everything but new suspension bushings and in she goes.












Big upgrade going from an open diff/1310 yoked/8.5"/3.08 gearing to g80 locker/1350 yoked/9.5"/3.42 gearing rear end. I think some of the other people in this thread will be pleased I finally did a re-gear, and frankly so am I. It helped tremendously with drivability, converter flashing, gave me some traction control and I don't need to worry about breaking this heavy duty 9.5" semi-float axle adding any more power. A++ would do this mod again!