GMT900 6.2 PPV Build Log

[ls3_ppv]

Hi, I am car enthusiast or perhaps a professional idiot. Either way, I have a 2010 Tahoe PPV and I wanted to start a build log to share with the class my journey with this vehicle and perhaps shed some light on GMT900 ownership in the good and bad ways. I believe the forum format lends itself well to a build log and while I have had the PPV for a minute now, its in a place where I want to share the process.


In June of 2021, I was having some issues with my daily driver. At the time, I needed something with a hitch and decent tow capacity. Having two dogs to haul around and needing a hitch makes an SUV a logical choice for me. I happened across a dark gray PPV that was in decent shape exterior-wise with a very clean interior AND an LS3 already dropped in it. This really scratched that itch for me to have something fun and unique to daily. With an LS motor even souped up should make for a reliable daily. Here it is the day I bought it and brought it home.

Plasti-dipped stock wheels aren't my favorite but I bought this car for the spec and drivetrain. We can fix that later...

 

[ls3_ppv]

With the chassis having nearly 200k miles on it, a refreshed motor already dropped in and running was a welcome part of the purchase deal I made. Seller had pictures of the work and enough receipts that I was convinced and drove out of state with a buddy to bring it back home.

Proper LS3 shortblock w/flat top pistons
BTR 225/238 cam
BTR pushrods
BTR springs
LS9 head gaskets
Speed Engineering headers
Tick performance oil pump
5364 heads
Circle D converter
Upgraded kolene clutch pack
Corsa intake
AFP poly engine mounts
ARP head studs
Spintech mufflers

PPV goodies included:
Dual batteries
Uprated alternator
Integrated wiring for accessories throughout
Rubberized flooring
140mph certified speedo
Transmission temp readout in the cluster
26gal fuel tank
Lowering springs
Power steering oil cooler
no third row, no onstar and no tow mode button

But some of the cop red/white lights still worked so that's cool. This PPV only got a 3.08 rear gear open diff housed in a basic chevy 10 bolt rear end. I'd later come to realize how a hog ass cam, high stall coverter, LONG highway gear and heavy vehicle are not well matched together.

Documentation on the GMT900 PPV: LINK

Seller advised me that the 6L80 needed a tune, engine needed an upgraded valley cover and better catch can. (Oddly specific recommendations, hmmm...) He tried to do a burnout but with an open diff it just boiled one tire. I paid for the vehicle and headed back home 4 hours away without incident

Sweet idle video seller sent over:

Me behind the wheel somewhere near Atlanta on the drive home

 

[Joseph Garcia]

Very nice project truck. Time to put a blower on it.

 

[Marky Dissod]

This PPV only got a 3.08 rear gear open diff housed in a basic chevy 10 bolt rear end.
I'd later come to realize how a hog ass cam, high stall converter, LONG highway gear and heavy vehicle are not well matched together.

Time to put a blower on it.

Instead of a blower, far more value would be achieved as follows:
3.73 and whatever limited slip of your choice (3.42 if highway is that much more important than metro / urban / city)
NORMAL stall converter (6L80 w/ 4.03 1st gear makes a higher stall converter dumb in the context of better gearing)
Shifter with 'Tow / Haul' mode, for 2 different shift modes after you get it tuned, instead of settling for just one
(who doesn't want two shift modes?)

Before you put the engine in, is the LS9 gasket thicker than a normal (non-supercharged) gasket?
Because if the gasket is thicker than normal, not only does it take away from the quench and RAISE the minimum safe octane,
it also makes that hogass cam even more ill-suited to your heavy vehicle than it already is.

I'll always prefer an SSV. That said, your PPV proves that GM should have put a 6.0L or 6.2L in every PPV.

 

[kbuskill]

Instead of a blower, far more value would be achieved as follows:
3.73 and whatever limited slip of your choice (3.42 if the highway is that much more important to you than metro / urban / city)
NORMAL stall converter (a 6L80 with 4.03 1st gear makes a higher stall converter dumb in the context of better gearing)
Shifter with 'Tow / Haul' mode, for 2 different shift modes after you get it tuned, instead of just the one (who doesn't want two shift modes?)

Before you put the engine in, is the LS9 gasket thicker than a normal (non-supercharged) gasket?
Because if the gasket is thicker than normal, not only does it take away from the quench and RAISE the minimum safe octane,
it also makes that hogass cam even more ill-suited to your heavy vehicle than it already is.

I'll always prefer an SSV. That said, your PPV is proof that GM should have put a 6.0L or 6.2L in every PPV.

Just curious, why/how would a thicker head gasket "RAISE the minimum safe octane"?

A thinner head gasket would raise the compression ratio and require higher octane, wouldn't it?

 

[ls3_ppv]

Before you put the engine in, is the LS9 gasket thicker than a normal (non-supercharged) gasket?

Too late, the 6.2 was in it before I bought it. LS9 head gaskets are thicker than normal LS head gaskets. I didn't get the machine shop build sheet on this 6.2 rebuild from the previous owner, its hard to say what effect the LS9 head gaskets had. Block could have been decked, heads could have been milled down a lot. It ran and drove me home.

 

[Marky Dissod]

Just curious, why/how would a thicker head gasket "RAISE the minimum safe octane"?
A thinner head gasket would raise the compression ratio and require higher octane, wouldn't it?

Little known fact:
LS/Vortec combustion chamber shape depends on the piston crowns sticking out ever so slightly above the bore at Top Dead Center.
Reducing the compression with a thicker head gasket reduces the effectiveness of the 'quench'.

Our combustion chamber designs are made less effective by lowering the compression with a thicker gasket.

Quench: Unlocking Performance Squished Between the Piston and Head

Quench is the clearance between the piston and cylinder head at TDC. It can affect engine effeciency and performance, if you truly understand it.

www.enginelabs.com

 

[kbuskill]

Little known fact:
LS/Vortec combustion chamber shape depends on the piston crowns sticking out ever so slightly above the bore at Top Dead Center.
Reducing the compression with a thicker head gasket reduces the effectiveness of the 'quench'.

Our combustion chamber designs are made less effective by lowering the compression with a thicker gasket.

Quench: Unlocking Performance Squished Between the Piston and Head

Quench is the clearance between the piston and cylinder head at TDC. It can affect engine effeciency and performance, if you truly understand it.

www.enginelabs.com

So you are saying that the thicker head gasket, reducing quench/compression, will be less efficient at keeping the engine from detonation and therefore require higher octane to compensate for the increased chance of detonation, if I am understanding you correctly.

 

[ls3_ppv]

I had the PPV for about a month before I started to mod it. I found it needed some new front brake pads and well why not just do new calipers? Its got 200k on them, probably original anyways. From these forums I discovered the 4 pot bolt on brake upgrade from the 2019+ silverados. I ordered a set, powdercoated them and put them on along with a new oem brake booster. Very nice improvement in pedal feel, definitely more confidence inspiring than the "heavy duty" gmt900 ppv brakes. Not bad for less than $500 all in!

2019+ 4pot brake upgrade

Brake Swap List
Caliper Front Right 13536580
Caliper Front Left 13536579
Splash Shield Left 84080138
Splash Shield Right 84080137
Front Rotor 13514522 ....13.5" rotor
Front Rotor 13514522
OEM Pads 84847749
Disc Brake Pad Pin Kit 13513399
Disc Brake Pad Pin Kit 13513399

As I previously mentioned this thing was on tow duty, brake upgrades are always a good idea for a tow pig.

And towing a trailer to go collect another shitbox.

 

[ls3_ppv]

I sadly cannot find pictures of the exhaust that came on the PPV but what a pile of crap it was. I smelled fumes big time from day one driving it anywhere and initially chalked it up to the headers, aftermarket mufflers and piping. Turns out the flanges at the collectors of the speed engineering headers were chopped off for some reason and the previous owner had some crazy ideas for booger welding in a crossover pipe and the spintech mufflers. The chopped off collectors were fiberglass wrapped after booger welded to try and get them to stop leaking on the top side of the collectors because the PO welded the entire exhaust together in the car. There were no sections and I realized any further exhaust mods meant cutting out what I had and starting over. This was the first indication that the previous owner was not the performance guru he was trying to convince me that he was.

Well its getting into the end of August now and I wanted to take this thing to LSfest East. So I chopped off the section after the header collectors, swapped the spintechs out for some magnaflows to quiet it down and take out some rasp. Here you can see the spintechs with the turndowns have been replaced with some straight tips off the magnaflows. I also replaced the rear trunk emblem that was missing and hit it with a few coats of black and clear. Off we went to Bowling Green, KY!

I get a timeslot for the dyno and got some data on where the car stood.

I though this seemed low for a 420bhp 6.2 with a big cam but maybe that 6L80 really is sapping a lot of power. I expected at least 400whp with the cam and exhaust.

Cleet even made an appearance at this LSfest, I was stoked!

At LSfest, I approached one of the guys at the HPtuners vendor tent and had some questions. I knew the PPV was running like shit, would die sometimes coming to a stop and had some general drivability issues. Guy asked if the PPV was at the campground, grabbed his laptop and walked over. A literal quick & dirty campground tune would be flashed and run on this vehicle for about 10 months more. Drivability and shifting was much improved, still only 6-7MPG though. Yikes! But I craved more, LSfest gave me some ideas that i couldn't shake and they were followed by some poor decisions. Ideas were great but the execution was bad.

 

[Marky Dissod]

So you are saying that the thicker head gasket, reducing quench/compression,
will be less efficient at keeping the engine from detonation,
and therefore require higher octane to compensate for the increased chance of detonation,
if I am understanding you correctly.

Purpose of quench, especially in a wedge combustion chamber, is to enhance mixture motion.
During the squeeze, the 'flat' area of the piston rises to nearly meet the 'flat' area of the head.
They may not be truly flat, they're shaped so that combustion canNOT take place in those areas.
They instead push the air/fuel mixture toward the largest part of the combustion chamber in motion like bellows.
The further apart the 'flats' are, the less mixture motion is induced.

Other ways to avoid ping / knock are to choose the cam carefully, to write the spark tables carefully,
to choose the correct octane, and to achieve finer fuel atomization, which GM combined with more quench.
Compare the Gen5 pistons to the Gen4 pistons, then compare the Gen4 pistons to the Gen3 pistons.
As the piston chamber has evolved, so has the static compression ratio.

 

[ls3_ppv]

I noticed the PPV was burning oil and needing topped up about every two weeks. This motor didn't live an easy life, it was loud but slow and I had places to be. It came with an ebay catch can on the passenger or PCV clean side and i did what any professional idiot would do and remove that to upgrade to an even bigger catch can! As a master level internet sleuth I set to reading about catch cans, how they work and why they are needed. Since I was catching oil here but burning more oil than was caught I tried to vent to atmosphere from both valve covers based on what the internet told me. (lol)

Here is the catch can the PO put on the car. He mentioned I should upgrade this and the HPtuners guy commented it was weird to only have a can on the PCV clean side instead of the dirty and clean side or just the dirty side. Blue line connected the corsa intake to the can and provided a filtered fresh air feed. Green line routed to the PCV connection on the passenger valve cover. Let's call this PPV PCV rev. 1

Anyways, lets throw that away and install another ebay catch can! Spoiler: it didn't work BUT I did learn how to make AN lines even if they are scuffed up. Actually it did work to catch crankcase vapors, problem was it simply saturated the filter and oozed oil simply venting to atmosphere. Oh and there is no vacuum on the crankcase which helps to seal up piston rings, maybe prevent oil loss. I'd come to learn the err of my ways even if the internet told me this is the way. Lets call this PPV PCV rev. 2

 

[ls3_ppv]

I went back to the drawing board, there was improvements that needed to be made to the PCV system on this car. So I came up with this terrible drawing and this contraption of a PCV catch can setup.

I didn't realize until now that I had come up with a viable PCV system for a naturally aspirated LS motor. We have vacuum at all times pulled through the crankcase via the top connection of intake manifold, blowby cannot push into the intake tube, the catch can is now on the PCV dirty side of this motor and we can still vent excess to atmosphere after going through the catch can. Let's call this PPV PCV rev. 3

This worked, it worked well I might add. This was installed in April of 2022 and used for about 5 months. Bit of foreshadowing here but the only change needed to make this suitable for boost is an additional check valve on the connection between the intake manifold. Easy day! And unfortunately this idea of boost was also poorly executed....

 

[RooTBeeRthe1st]

Got to say, I'm interested to see what the next 2.5/3 years of your ppv's life consists of.

 

[swathdiver]

My bone stock 6.2 L9H puts down 372 rear wheel horsepower through the traps in the quarter mile.

Before you mod the motor to try and bring the power up, change the gears.

You can put a trutrac in the 8.6 or you can get a 9.5" 14-bolt out of a RWD Escalalde/Denali with 3.42 gears and then re-gear it. A P265-70-17 tire, being taller than stock PPV, will help a little in keeping the tires planted. Of course, the choice of tire is important in this endeavor. Michelin Defenders serve us well at the drag strip and on the street.

Those LS9 head gaskets by themselves would have dropped your compression ratio. We don't know if the block and heads were milled down and what pistons are in it to know for sure. L9Hs require high octane gasoline or E85.

Drivetrain losses on my 5.3 and 6.2s are just under 8%, the 6L80 and 9.5" axles are very efficient. If your circle D torque converter is a billet type, it will sap a bit more horsepower to turn it with the extra rotational weight.

Fun stuff!

 

[ls3_ppv]

Fast forward to August 2022, I've spent a bunch of time reading the advantages of a blower vs a turbo and for me it boiled down to a couple things. I like the torque of a positive displacement blower but seemingly every LSA swap suffers from belt slip and you'd be reworking the factory accessory drive which was not cheap, pinning the crank, going to an 8 or 10 rib crank pulley, etc. Remedies were out there but I wasn't a fan of spending 4-8k for a boostdistrict LSA or magnuson package and needing to put a few thousand more into it potentially. The huge upside to a supercharger kit is that its bolt on, remove the stock intake manifold, slap on injectors and change your accessory drive bits and you are pretty much done. It's fully reversible and retains a good bit of value used if I ever need to sell. Install is a weekend ordeal and you are back on the road.

HOWEVER (lol) a turbo, well that's a value proposition for my lizard brain. Sure you gotta rework the exhaust completely, come up with intercooler piping custom for the vehicle, create a provision for the turbo oil drain, tap in somewhere for oil feed to the turbo. Unless you have some experience doing turbo installs in general or spend a lot for a well put together kit (huron speed, fahler maybe?) this is NOT a bolt on affair. So I did the only reasonable thing and bought about the cheapest kit I could find on ebay, it says it fits my year and model vehicle and they wouldn't lie about that would they? After all, I hate the exhaust setup still on this vehicle and installing a turbo would allow me to cut it all out so the additional hurdles are worth it to me.

I stumbled across MMI speed shop, hoo boy. On sale for less than half the cost of a basic LSA supercharger package and free shipping to boot! Wow what a steal, I couldn't hit the buy button fast enough. This place was offering a "complete" single turbo kit and I am here to tell you that I threw most of that damn kit in the trash. Their hotside and downpipe are decent but the intercooler, intercooler piping, turbo, brackets, wastegate and BOV are all dog water. I hadn't realized the headache I just bought myself.

Parts delivery and inspection:

Install day and removing this amateur hour exhaust system, you can see here I'm noticing that the AC and heater hoses are going to get crispy when that turbo goes in:

 

[ls3_ppv]

I didn't even try and use the MMI turbo kit intercooler, it was TINY! But I did have this unit sitting around, so it'll have to do. Had some spare exhaust piping and eyeballed the angles, fabbed a bracket to the core support, hit the intercooler piping with some black paint and put it in place. This intercooler was at least twice as tall and slightly wider than the one that came in the kit.

I am sure some of you will be right along to tell me how small this turbo is trying to feed a hungry 6.2 liter motor. And I would completely agree with you. It was a 62mm smol boi and with this big cam that wanted to breath up top in the RPMs it was also not matched well. Seems to be a theme for this vehicle.

Completely installed, base tune loaded to get it back home and if you'll notice there is also a Mighty Mouse breather on the passenger valve cover now. It is check-valved and I put it into place to be able to visualize the blowby, I noticed I was having some at idle now. But this is my first LS turbo and I thought maybe that's normal? (spoiler: no its not.) But damnit I have a boosted LS3 now and its making all the right noises that my pants stay tight starting this thing up and driving it around.

Turbo PPV first Cars & Coffee, I'm riding high on my sense of accomplishment and ran into another souped up gmt900 PPV. He had a 6.0L iron block and LS3 heads swapped in his. I took it as a sign of good luck!

 

[ls3_ppv]

When you add more air, you gotta add more fuel. So I made probably the first in the line of good decisions for this build and selected a drop in, bucketed 415LPH fuel pump and some 900cc injectors from Deatschwerks. I've been involved with a couple more LS motor builds and tuning since then and I cannot stress enough how important it is to select a reputable injector company that has responsive support and provides good injector data. Deatschwerks gets two thumbs up from me, I even got to chat with some of their engineering team at LSfest East. Great company to deal with!

DW400 pump 9-401-7015

I also picked up fuel pressure, boost and wideband gauges from AEM and installed them into a Glowshift triple gauge pillar. Very happy with these part choices, all of which are still in use. The serial and analog outputs from the AEM wideband work natively with HPtuners and can be used to activate things like lean safety controls too. Top notch products, quality and fitment from AEM and Glowshift here too.

 

[ls3_ppv]

Got to say, I'm interested to see what the next 2.5/3 years of your ppv's life consists of.

Going back over the saved photos and reliving this is more exciting that I expected it would be. Appreciate the kind words!

 

[ls3_ppv]

My bone stock 6.2 L9H puts down 372 rear wheel horsepower

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.

Before you mod the motor to try and bring the power up, change the gears.

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.

P265-70-17 tire

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.

If your circle D torque converter is a billet type

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.