5.3L LS Small Block Build - Modern Mouse, Part 7

Sucp 1206 000 3L Ls Small Block Build Part 7

From day one, the idea behind Modern Mouse was to subject the 5.3L LS to all manner of testing, including everything from bolts-ons to blowers. Nitrous, a stroker upgrade, and even old-school carburetion helped round out the battery of tests, but the LM7 (now stroked to 383 cubic inches) emerged not only unscathed, but begging for more.

Subjecting Modern Mouse to all this abuse helped demonstrate the gains offered by various modifications. This in turn helps readers make informed decisions about which route to take when it comes time to modify their own ride. The impressive power output offered by the stock and modified 5.3L also makes a compelling case for choosing the little LM7 for your Chevy-powered hot rod in the first place. You might think that after six different installments, we would run out of things to test, but we have just scratched the surface. This month, we decided to introduce not just Modern Mouse, but a pair of LM7s to turbocharging. Confused? Read on!

Test 1 Single Turbo: Stock 5.3L LM7

Though Modern Mouse was currently sporting no less than 383 cubic inches, we decided to take a step back and illustrate the gains offered by turbocharging to two different 5.3L combinations. We were lucky enough to secure a second stock LM7 to run our first test this month. We figured running both stock and modified combinations would help our readers--after all, not everyone is going to build a duplicate of Modern Mouse.

The stock 5.3L was purchased from a local wrecking yard at an exceptional price, but we soon found out why. The LM7 take-out was advertised as complete, but was actually missing the throttle body and exhaust manifolds. It also had a cracked oil pan.

We cured this situation with an Accufab throttle body and a Moroso F-body pan we had from a previous test. The stock motor was run with a set of QTP long-tube headers and an electric water pump. For the single turbo, we got a set of JBA shorty headers. Tuning was provided by a FAST XFI/XIM management system and a set of 36-psi injectors. Run in stock trim (after optimized tuning), the 5.3L produced 361 hp at 5,400 rpm and 386 lb-ft of torque at 4,600 rpm. Torque production exceeded 350 lb-ft from 3,200 rpm to 5.400 rpm.

The 5.3L was then subjected to boost from a single turbo kit from HP Performance. The kit was designed for a Chevy truck, but it illustrated the potential of boosting a stock 5.3L perfectly. The kit included a dedicated Y-pipe that hooked directly to the stock exhaust manifolds (or our shorty headers). Though available with different turbos, we chose a 67-mm T4 HPQ turbo from Precision Turbo. It was capable of supporting nearly 800 hp on the right application, so it had no trouble on this otherwise stock 5.3L.

The kit from HP was available with and without an intercooler, and we elected to try it both ways. Run on pump gas at just under 8 psi in non-intercooled form (with a safe tune), the turbocharged 5.3L produced 510 hp at 5,400 rpm and 521 lb-ft of torque at 4,700 rpm. Adding the intercooler allowed us to increase the boost pressure to 11.3 psi, where the turbo 5.3L pumped out 608 hp at 5,700 rpm and 641 lb-ft of torque at 4,700 rpm.

Test 2-Twin Turbo-- Modern Mouse

Unlike the stock 5.3L, we built a custom twin turbo system for Modern Mouse. Though custom, the system illustrated what is possible with properly- sized turbos on an already powerful normally aspirated LM7 combination. The twin turbo system featured a pair of 76-mm turbos combined with a twin-core, air-to-water intercooler that featured dual 3-inch inlets and a single 3.5-inch outlet all from CX Racing.

1 Before putting boost to Modern Mouse, we decided to illustrate what turbocharging can do to a stock 5.3L. The new boneyard 5.3L was first run normally aspirated to establish a baseline. Running long-tube headers and an Accufab throttle body, the LM7 produced 361 hp and 386 lb-ft of torque.
1 Before putting boost to Modern Mouse, we decided to illustrate what turbocharging can d
2 Don't count out the stock truck intake for turbocharging, as the impressive torque production helps spool up the turbo.
2 Don't count out the stock truck intake for turbocharging, as the impressive torque prod
3 The turbo kit from HP Performance was first run in low-boost mode without an intercooler. Running 7.8 psi of boost, the turbo 5.3L produced 510 hp and 521 lb-ft of torque. The Ford MAF was used as a reducer to attach the 3-inch discharge tubing to the Accufab throttle body.
3 The turbo kit from HP Performance was first run in low-boost mode without an intercoole

4 Adding the intercooler allowed us to increase the boost pressure to 11.3 psi. This increase in boost pushed the power output of the stock 5.3L to 608 hp and 641 lb-ft of torque. Not too shabby for a junkyard mill.
4 Adding the intercooler allowed us to increase the boost pressure to 11.3 psi. This incr
5 After running the single turbo on the stock 5.3L, we turned our attention back to Modern Mouse, You will remember from previous installments that Modern Mouse was now sporting 383 cubic inches.
5 After running the single turbo on the stock 5.3L, we turned our attention back to Moder
6 The 383 stroker was plenty stout thanks to a set of forged pistons from Probe Racing, a set of Fel Pro head gaskets, and ARP head studs.
6 The 383 stroker was plenty stout thanks to a set of forged pistons from Probe Racing, a

7 Back in part four, we swapped out the milder grind for a Comp hydraulic roller cam. The healthy Comp cam offered a .617/.624 lift split, a 231/239-degree duration split and 113-degree LSA.
7 Back in part four, we swapped out the milder grind for a Comp hydraulic roller cam. The
8 For our turbo test, we installed a set of CNC-ported LS1 heads from Procomp Electronics. The 220cc intake ports flowed over 320 cfm.
8 For our turbo test, we installed a set of CNC-ported LS1 heads from Procomp Electronics
9 The CNC work on the LS1 heads from Procomp Electronics included the combustion chambers. A portion of the impressive flow figures can be attributed to the 2.055/1.60 valve package.
9 The CNC work on the LS1 heads from Procomp Electronics included the combustion chambers

Additional components included a pair of 45mm Hypergates and a single RacePort blow-off valve all from Turbo Smart. The exhaust system featured shorty truck headers from JBA connected to the turbos using short tubing sections designed to adapt the stock exhaust flanges to the T4 turbos. The Turbo Smart Hypergates were positioned inline on the adapter tubing, while the single RacePort blow off valve was welded to the single 3.5-inch aluminum inlet tube.

CXRacing also supplied the necessary 3-inch aluminum tubing, couplers and clamps to connect the turbos to the intercooler as well as the 3-inch stainless tubing, v-band flanges and clamps used to complete the exhaust. In addition to offering complete kits, CXRacing was a one-stop source for our do-it-yourself turbo kit. The final upgrade was to replace the 36-psi injectors with a set flowing 75 lbs per hour.

With Modern Mouse ready to rock, we first dialed in the air/fuel mixture at just seven psi before working our way up in power. Even at just over 7 psi, Modern Mouse produced nearly 750 hp. Eventually the boost was increased to nearly 13 psi (12.8 to be exact), where Modern Mouse pumped out 963 hp at 6,500 rpm and 868 lb-ft of torque at 5,000 rpm. Torque production exceeded 800 lb-ft from 4,650 rpm to 6,300 rpm, but never dipped below 700 lb-ft.

Being so close to 1,000 hp, it took all of our will power to stop from cranking up the boost. In the end, we decided to limit the boost to a reasonable level.

10 All testing on the NA and turbo combinations was run with the FAST XFI/XIM management system. Fast also supplied the necessary 75-pound injectors for our turbo motor.
10 All testing on the NA and turbo combinations was run with the FAST XFI/XIM management
11 We ran Modern Mouse normally aspirated prior to the installation of the twin turbo system. Obviously the heads from Procomp Electronics worked well, as the 383 responded with peak numbers of 539 hp and 516 lb-ft of torque.
11 We ran Modern Mouse normally aspirated prior to the installation of the twin turbo sys
12 The custom turbo system utilized JBA shorty truck headers feeding custom tubes to adapt the stock header flange to the T4 turbo.
12 The custom turbo system utilized JBA shorty truck headers feeding custom tubes to adap

13 CX Racing supplied a pair of 76-mm turbos. In truth, these were more than we needed for Modern Mouse (they also offer smaller 67-mm and 72-mm versions), but we had them on hand. Each of the T4-based, 76-mm turbos featured a 4-inch compressor inlet, a 2.5-inch discharge and 3-inch exhaust outlet. The exhaust system consisted of a pair of 90-degree, 3.0-inch stainless steel elbows.
13 CX Racing supplied a pair of 76-mm turbos. In truth, these were more than we needed fo
14 To ensure proper boost control, TurboSmart supplied a pair of Hypergate45 waste gates. The trick threaded collar design not only decreased overall size to improve fitment, but facilitated easy spring swaps. The waste gates were secured to the dedicated waste gate flanges using V-band clamps.
14 To ensure proper boost control, TurboSmart supplied a pair of Hypergate45 waste gates.
15 TurboSmart also supplied one of their RacePort blow off valves. A high-flow blow off valve is a necessity on high-boost/power applications. The blow off valve opened to provide pressure relief during shifts or lift-throttle applications. Without the valve, the pressure wave that flows back after slamming into the closed throttle body would try to escape back out the turbo. Attempting to instantaneously stop or reverse the flow of an impeller spinning upwards of 100,000 rpm is not a good situation! The RacePort shared the threaded collar design with the new Hypergates.
15 TurboSmart also supplied one of their RacePort blow off valves. A high-flow blow off v

16 Keeping things cool was a dual-inlet, single outlet, air-to-water intercooler from CXRacing. Capable of supporting over 1,500 hp, the dual-core system was supplied dyno water for this testing. CXRacing also supplied the necessary 3.0 and 3.5-inch aluminum tubing, couplers and clamps to complete our custom kit.
16 Keeping things cool was a dual-inlet, single outlet, air-to-water intercooler from CXR
17 With everything finally assembled, we were finally ready to run Modern Mouse under boost. We started at the lowest boost setting (7-psi waste gate springs) and worked our way up to just under 13 psi. Even at 7.3 psi, Modern Mouse pumped out nearly 750 hp, but things got really interesting once we cranked it up. Running 12.8 psi, the turbocharged 383 produced 963 hp and 868 lb-ft of torque.
17 With everything finally assembled, we were finally ready to run Modern Mouse under boo
18 Stock LM7 5.3L-NA vs HP Performance Single Turbo (8 & 11.3 psi) The stock 5.3L was run with a set of long-tube headers, 36 psi injectors, and FAST XFI/XIM management system. Run in normally aspirated trim, the 5.3L produced 361 hp and 386 lb-ft of torque. Running with the Precision turbo on the single turbo kit from HP Performance resulted in 510 hp and 521 lb-ft of torque at just under 8 psi. Adding an intercooler and increasing the boost pressure to 11.3 psi resulted in a jump to 608 hp and 641 lb-ft of torque. At this point, the stock combination would benefit greatly from a cam swap.
18 Stock LM7 5.3L-NA vs HP Performance Single Turbo (8 & 11.3 psi) The stock 5.3L was r

SOURCES
Comp Cams/Fast 3406 Democrat Road Memphis TN 38118 800-999-0853 www.compcams.com	Procomp Electronics 605 S. Milliken Avenue Unit A Ontario CA 91761 909-605-1123 www.procompelectronics.com
Holley/Hooker 1801 Russellville Road Bowling Green KY 42101 270-782-2900 www.holley.com	L&R Automotive 13731 Bora Drive Sante Fe Springs CA 90670 562-802-0443 www.lnrengine.com
Probe Racing 2555 West 237th Street Torrance CA 90505 310-784-2977 www.probeindustries.com	CX Racing 626-575-3288 www.cxracing.com