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215 Posts
Discussion Starter · #1 ·
Starting a build thread on my Shop Car, the Box Caprice. Going on it's third LSx based combo since I have owned it (5th motor combination overall if you count the SBC builds).

I will try my best to keep this updated in between shop work. It's hard to squeeze time in to work on it, but I have 90% of the parts to button this thing up and finish the fab work.

In addition to the updates, I am also keeping a running tally here on the bottom of the first page of what I have spent so far. Hopefully this will help anyone out who is looking to duplicate a similar combination.

Last Year:

Here are the highlights of last years mess of a build haha.

2004 4.8L LR4 200k Miles+
Comp Thumpr Camshaft
Brian Tooley Springs, Trickflow Pushrods
Holley Modular Mid-Rise
Garrett/ Precision Ancient 70MM
Turbonetics RG45
4" Fender-Exit
4L80e Manual Shift with a Brake

3rd Gear Burnout Turbo LSx Caprice Classic - YouTube


Few pics of the current mock-up ;)

Quick run-down of the combo...

-2007 Aluminum 5.3 Just Freshened (rings, bearings, decked hone and line bored. OEM Rotating assembly).
-243 Heads Resurfaced w/ BTR Platinum Spring Kit
-Cometic Gaskets and ARP Studs
-TBSS/NBS Intake Manifold
-EBAY China Headers Forward Facing
-Twin VS Racing China GT45s (69mm compressor, 1.05 divided exhaust)
-Turbosmart 45mm Hypergates
-E38 PCM & Re-Worked Harness from 2008 LY6
-DBW 87mm Stock Throttle Body
-Built 4L80E (TCI 300m Input & Reverse Pattern Full Manual Valve Body w/ Brake)

In order to get the turbos to light, I am going to experiment with blocking half the divided housing entrance to reduce the housing a/r. If on the back-pressure log it appears to be hurting up top. I will play around with slowly opening it back up. Similar to a manual "quick-spool valve" if you can imagine.


Running Tally of Cost to Build:

-2007 5.3 LC9 -200.00- (aluminum block, 243 heads, complete intake w/ 87mm throttle body; had a skip & no coils included)
-Modified TBSS/NBS Fuel Rails -100.00- (welding labor and parts on modified OEM stainless rails with welded -8AN fittings for return system)
-Ford Racing 80lb Injectors -300.00- (purchased used. Previously installed for dyno time only)
-2008 LY6 Harness & ECU & TCM -25.00- (paid 100.00 & sold TCM for 75.00)
-ZR1 3Bar Map Sensor -Free- (previously used on another project)
-New DBW Pedal From GM -45.00- (used vin from harness/ ecu donor vehicle)
-Custom Grind Cam from Geoff @ EPS -420.00- (222/226 .604/.605 113+2)
-BTR .660 Lift Platinum Spring Kit -220.00- (steel retainers)
-VS Racing GT45 Clones x2 -600.00- (including gaskets and downpipe v-band & clamp)
-Turbosmart 45mm Hypergates x2 -675.00- (7psi spring black)
-Ebay Forward Facing Turbo Headers -180.00- (bought used from mock-up motor with hardware, v-band & clamp)
-Schedule 10 Reducers x2 -44.00- (304 stainless 2.5"x2" for headers to hot side)
-Schedule 10 45* x2 -15.20- (304 stainless 2" 45*)
-Schedule 10 Straight -Free- (scrap 2" from previous build)
-GMPP Valve Covers -263.28- (two left hand side w/ grommets)

Current as of 4/9/2015: 3,087.48

· Registered
215 Posts
Discussion Starter · #3 ·
This will be good, what are your power goals with the twin hairdryers?
However much I think the motor will safely take at full boost. Just going to ramp into it easily. Really not sure what to expect. I am going to be on E85 again, so the 80s will be the limiting factor until i step up to some Injector Dynamics.

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215 Posts
Discussion Starter · #6 ·
Wastegates are mounted up on the hot side. Not sure if I am going to run the dump tubes separately or if I am going to dump them back into the downpipe. We'll see once the motor is sitting back in the chassis.

Compressor covers are clocked and painted with the Rustoleum industrial flat black. I love that stuff! Also shot the hot side with some Rustoleum grill paint, which works equally well. No reason you can't make junk look good! haha


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4 Posts
Very cool build! I do have a question about blocking off the exhaust housing to reduce the a/r. If you block it off wont you be restricting flow which helps maintain a smooth boost graph. Kind of the argument that the n/a guys have about a small diameter header vs a large diameter header. I guess if all the exhaust was funneled down it would move your torque and hp numbers lower in the rpm range but it would also put a lot more stress on the motor. From my experience too much low end boost bends rods and really plays hell on the valve train.

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770 Posts
What happened to the original setup? Did something fail or was it too slow?

I'm looking to do a single turbo setup in the future

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