GMT900 6.2 PPV Build Log

[ls3_ppv]

April 2024, the PPV is chugging along. I am working on the back and forth revisions and datalogs with the remote tuner and trying to iron out some minor shifting issues during various throttle loads. But of course, you can't sleep on the deals. I was crusing FB marketplace and happened upon a VSracing 78/75 billet gen2.5 series turbo. .96AR T4....well uhh thats exactly the upgrade this PPV needs. That 64mm ebay turbski is choking this 6.2 motor out in the upper rpms, guy wanted $200 for it with less than a dozen 1/4 mile passes on it before he upgraded. He already tapped it for a boost reference push lock fitting at the outlet and oil fitting came with it. Even offered to deliver it to me, buddy how could I not!?

So anyways, its time to get serious about some power...



Also a good time to heat wrap that downpipe. This stuff really sucks to work with but its a big difference in under hood temps.


I also take a quick peak under the valve covers and make sure things aren't going sideways on me again. She's mint bud!

 

[ls3_ppv]

Retune the PPV and with a new motor and turbo I just want to rack up some miles on this thing. We head back to LSfest again in September 2024 as the PPV has been trouble free since April and about 8000 miles now. Some interesting match ups on the track at Beech Bend raceway lol


PPV makes the trip there and back but I'm noticing that the oil pressure is tending lower. About 18psi at hot idle now when it used to be closer to 30psi. I change oil and send out for a blackstone oil analysis, lead levels are slightly elevated.... for tracking here were lead levels all 8000 miles.

Mileage / Lead PPM
300 / 5
2200 / 2
5211 / 3
8039 / 7

Blackstone flagged the 5ppm and 7ppm reading which indicated it was higher than universal averages and we needed to keep an eye on it as lead is from bearings.

Disaster strikes....again in December 2024. Different failure mode, same headache. Before I pull the motor again its confirmed with a mechanical gauge. 14psi cold idle, 4psi hot idle.


Out she comes, yea PHQ is right lol.


Camshaft bearing #4 has left the chat...


I also mic'd out the oil clearance on the other bearings and they are all above the service limit of .005" and consensus is you really want something in the neighborhood of .002-.003 on new cam bearings. A little self-clearancing by the lifter on that #4 bearing.


I am not going to lie, I am pretty disheartened at this point. I consult with the machine shop on wtf has happened here but at 8000miles there is no warranty. If you have been following along, you will remember that the only thing I reused was the camshaft and while its journals were the proper size I didn't trust it any more. Also found that the rear oil galley barbel slid aft and an O-ring on it had failed. A momentary drop in pressure when this happened I suspect caused the mayhem. This oil pump was fighting for its life to save this motor, that camshaft bearing sliding aft but staying partially in place allowed oil to keep things lubricated enough to prevent a bigger disaster. Cylinder bores, lifter bores, all bearing surfaces otherwise have zero damage. I'm not excited to spend two Christmas seasons rebuilding this turd, its certainly not my preference. But the story doesn't end here...we must keep going!

 

[ls3_ppv]

Let's get after it, this PPV isn't going to whoop me. And that cam, don't trust that. It's also not suited for a heavy SUV and boost. Let's go back with a Sloppy Mechanics "The Best Cam" LOL

Shopping list:
Durabond coated cam bearings PN: CHP-25T
Summit racing main bearings PN: SUM-172310
Summit racing race series coated rod bearings PN: SUM-663HC010
Melling HV HP oil pump PN: MEL-10296
BTR LS9 Multilayer Head Gaskets PN: BTR22033-2
Sloppy 219/225 cam


If someone wants to calculate the compression now here's the info I know:
deck height: 9.240 in.
block decked .005in.
heads milled .001in.
Piston Volume +3cc
Combustion Chamber Volume 70cc
Gasket thickness: 0.055in
Gasket bore: 4.1

I am coming up with a 10.6:1 compression ratio.

Interesting set of ACL...er I mean summit racing rod bearings I got...


Staying organized



Going through the heads, all valves seal up. No repeats of last year's fiasco.



Freshhhhhhhhhh





Been fighting a pesky leak at the back of each exhaust manifold, found they were both slightly warped. Got those resurfaced and problem solved!

 

[ls3_ppv]

I am a big fan of "while you are in there" mods. If you look at my earlier post installing the turbo kit, you will see that the driver manifold is a stock truck manifold with the 3 stud flange. Lets v-band the whole exhaust, fix the crappy flex section in the cross over and make things a bit more blue.

V band welded to end of driver manifold



Screw it, new cross over build. Fancy double walled accordion style flex piece from vibrant performance.


My boy being a major help getting this fitted and welded up!



Beautiful new crossover, fits better than the one that came out and should leak from the new driver side v band or flex section ever again.



And lastly, lets add some color to this welded bung valve covers. These came out beautiful, my painter buddy was asked to make it something blue and came up with this from a mix of some Lemans Blue BMW paint leftover from one of my other projects and some colors he had. He killed it!

 

[ls3_ppv]

Time to drop it back in, I am so ready to put this thing back on the road and boil some more tires!



Dropped it in with other valve covers, didnt want to damage these freshly painted ones. Once it was in and bolted up to the bellhousing, I swapped them out.



Hell yea, we got oil pressure now boys!



Man does it feel good to have this thing back out on the road, temps and oil pressure are solid.

 

[ls3_ppv]

Christmas came and my wife...I mean Santa brought me some goodies. New Dashskin dash cover and headlights landed. She's seen the headache I've been through and also drives this car from time to time and wanted to get me a little something.


Like every GMT900 vehicle, the dash cracks. Luckily I had all the pieces still and plastic welded everything up to reinforce it the best I could before putting the topper on.




Installed and silicone setting up, I put about 20 books and tension rods on this thing to hold it down for 24 hours. The smell lingered around for about a week.


All cleaned up and out on the road, this turned out very nice. No more rattling!

 

[ls3_ppv]

Headlights are clapped out with some LED bulbs that blind everyone and the plastic is cloudy. These came from an amazon seller Auto Dynasty for $105, I opted for the OEM style halogens with clear reflectors, clear lenses and black housings. Also tossed the LED bulbs and installed some Sylvania silverstar ultra bulbs.

Before:


After:





At some point I replaced the missing front lip on this thing too, that was less than $40 delivered to my door and installed in 5 minutes. This PPV headed into 2025 with a newly rebuilt motor, new cam, new crossover, new headlights, new front lip and new dashboard topper. I get it retuned and work through break-in and tune revisions with the remote tuner again. This thing is getting dialed in and looking better and better. I snapped a picture during the snowday we caught here recently and it was looking good that day.