TECH. If you liked our Danger Mouse and Major Mouse series of articles, you re gonna love this one.

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1 TECH Here Comes Modern Mouse! Following in the immortal footsteps of both Major Mouse and Danger Mouse is none other than Modern Mouse. Here Comes Modern Mouse! If you liked our Danger Mouse and Major Mouse series of articles, you re gonna love this one. By Richard Holdener Photos by the author If the past has shown us anything, it is that readers of Su p e r Ch e v y relish their small-blocks. Not that we don t show equal love to their big-block brothers, but there is something about a Mouse motor thumping out serious power that really gets the blood pumping. Loyal readers will remember the Major Mouse and Danger Mouse series that covered all manner of small-block performance. Though the original continues to fill the engine bays of countless performance machines, we decided to take an in-depth performance look at the current Gen III (and Gen IV) small-blocks, better known by enthusiasts as the LS engine family. Introduced to replace the original Mouse (Gen I) and LT1 (Gen II) engine families, the LS had tall shoes to fill, but came cocked, locked, and ready to rock. Ranging in displacements from 4.8 liters (293 inches) all the way up to 7.0 liters (427.5 inches), the impressive LS had plenty to offer, including cross-bolted blocks, high-flow cylinder heads, and even a factory windage tray. With so much to offer, we decided the current configuration deserved a series of its own enter Modern Mouse. The decision to start the Modern Mouse series was easy, but what exactly to start with somewhat less so. The wide range of factory displacements, configurations, and production power outputs made it difficult to choose a starting point. Given the current economic situation, we decided that (at the very least) Modern Mouse should start by embracing affordability. Sure, the series will eventually take us beyond the realm of low-buck bolt-ons, but they should still be covered in earnest. The combination of affordability and availability (the two are obviously interrelated) led us straight to the 5.3L (LM7) truck motor. Sure, the 5.7L LS1 and LS6, 6.0L LS2, or even a modern 6.2L LS3 will offer more power, but that extra grunt comes with a hefty price tag. Even the larger 6.0L truck motor commands a premium over the smaller 5.3L. The 5.3L (324 cubic inches) has become the small-block engine of choice, especially for cost-conscious buildups. Though down on displacement in stock trim, the 5.3L truck mill is high on performance potential (we look forward to punching this one out to 383 cubic inches). The Modern Mouse series will eventually take us through stroker cranks and boosted buildups, but for now we decided to concentrate on the basics. Knowing that many readers are looking at their 5.3L to serve as a daily driver, we decided to start Modern Mouse off with a few select performance upgrades, including heads, cam, and an intake. Before making any hardware changes, we took the software route by altering the factory tune. When all was said and done, we had a powerful, aluminum-headed small-block that would be perfect for any daily driver. Before getting Modern Mouse on the dyno, we took the liberty of making a few changes. After getting our 5.3L from a local wrecking yard (complete running motor for $395), we tore it apart to verify that it was indeed a 5.3L. The 5.3L and smaller 4.8L truck motors are externally identical. The internal differences included a change in stroke, connecting-rod length, and use of flat-top pistons on the 4.8L (The H.O. version of the 5.3L also runs flat-top pistons). The casting numbers identify the 4.8L (121 for rods and for crank), so make sure which engine you have. After ensuring our 5.3L was indeed a 5.3L (a 4.8L will respond to the proposed mods as well, just with slightly less overall power and torque), 048 / SUPER CHEVY /November 2011 SUCP MOUSE.indd 48 8/10/11 5:29:18 PM

2 Tech Here Comes Modern Mouse! The 5.3L may not be the most powerful factory offering, but the iron-block, aluminum-headed, truck motor was certainly the most popular, available, and affordable combination. Though our 5.3L was a running motor, we opted to upgrade to a new timing chain and oil pump from Speed Pro. Make sure to liberally coat the internal gears of the oil pump with assembly lube prior to installation. This will aid in priming the oiling system. 2 Since they are externally identical, we pulled the pan on Modern Mouse to verify it was in fact a 5.3L rather than the smaller 4.8L. The 4.8L features a shorter stroke (3.267 vs ) and longer connecting rods (6.275 vs ) than the 5.3L (identifiable by casting numbers of 121 and for the rods and crank, respectively). Unlike the original small-block, even the LM7 5.3L truck motor featured a factory windage tray. 4 With Modern Mouse already partially disassembled, we removed the stock heads and replaced the factory head gaskets with new units from Fel Pro. With boost and nitrous planned in the near future, we also opted to replace the factory head bolts with head studs from ARP. The factory gaskets and bolts will work fine on a stock or even mild performance application, but we had big plans for the little Mouse. 6 No stamped-steel rockers here, as the LS family was blessed with roller rockers right from the factory. In truth, the factory rockers featured roller fulcrums, but not rollerized tips. All testing was run through a set of 1-3/4-inch long-tube dyno headers. Headers are worth hp over the factory exhaust manifolds with measurable power gains through the entire rev range. 050 / SUPER CHEVY /November 2011 SUCP MOUSE.indd 50 8/10/11 5:29:20 PM

3 we took the liberty of making a few changes. Knowing that the future held both boost and nitrous for Modern Mouse, we elected to replace the factory head gaskets and bolts with upgrades from Fel Pro and ARP. Not necessary on this normally aspirated application, the upgrades were simply done in anticipation of future abuse. After reassembly, the 5.3L was installed on the engine dyno using a set of 1-3/4-inch headers, a Meziere electric water pump, and the FAST XFI engine management system. For the baseline test, we programmed the FAST to provide the factory timing and air/fuel curves (2003 truck application). Run with the mild factory tune, the 5.3L produced 343 hp and 372 lb-ft of torque. Letting our fingers do the walking over the keyboard, we tuned the XFI management system (more timing and less fuel) and dialed up the power output to 363 hp and 385 lb-ft of torque. To put these numbers into proper perspective, we ran replicas of the original 1970 LT-1 (370hp 350) and 1965 L76 (365hp 327) and neither of these muscle-car small-blocks eclipsed the power output of our stock 5.3L. Satisfied with our baseline numbers, it was now time for bolt-ons. First on the list of performance upgrades was a camshaft. This should come as no surprise, as nothing wakes up an LS motor like the right cam profile. The reason the 5.3L (any LS, but especially the newer 6.2L LS3s) responds so well to cam changes is that the motors offer such impressive head flow right from the factory. Stock LS heads (including the 706 heads on our LM7 5.3L) flow 225 cfm, or enough to support over 450 hp right out of the box. It takes a fully ported fuelie head to eclipse those flow numbers. With plenty of airflow, all the stock LS motor needed was more aggressive cam timing. For part one, we elected to cater Modern Mouse toward the daily-driver end of the spectrum, but fear not, as even wilder cam timing is on the way. To start, we chose a mild Comp XR265HR grind that offered a 0.522/0.529 lift split, a 212/218 duration split, and a 114-degree lobe separation angle. The XR265HR cam was just a step or two above the stock / 051 SUCP MOUSE.indd 51 8/10/11 5:29:21 PM

4 Tech cam, though the 5.3L offered the mildest production cam profile of the LS family. Power improved through the entire rev range with the XR265HR Comp cam, as the 5.3L belted out 385 hp and 412 lb-ft of torque. The cam improved the power output by as much as 30 hp at the top of the rev range. Happy with the results of the cam upgrade, we focused our attention on the cylinder heads. Like the original Mouse, aftermarket cylinder head choices abound for the LS engine family. Rather than splurge on a set of new heads, we decided to take the less expensive route and send the factory heads out for porting. The stock heads were removed and shipped out to Total Engine Airflow (TEA) for the company s Stage 2 port job. The heads were treated to full CNC port- 7 8 The 5.3L truck motor featured a composite, long-runner intake designed to optimize torque production lower in the rev range than the production LS1, LS2, or LS6 intakes / SUPER CHEVY /November 2011 SUCP MOUSE.indd 52 8/10/11 5:29:21 PM

5 8 ing, larger intake valves, and a valve spring upgrade that provided sufficient spring pressure and clearance to safely run lift cams and rev cleanly to 7,000 rpm. The TEA 5.3L heads flowed nearly 300 cfm, or enough to support over 600 hp on the right application. They were obviously more than sufficient for the needs of our mild 5.3L, but we liked the fact that they had plenty of potential should we elect to increase cam lift and/or cubic inches (we plan on both). The head upgrade improved the power output to 424 hp and 423 lb-ft of torque but (best of all) did so while maintaining idle vacuum. The power gains offered by the cam swap resulted in a slight drop in idle vacuum (less than 2 inches), but the head swap suffered from no such trade-off. The final performance upgrade Before the installation of our basic bolt-ons, we had to establish a baseline. The 5.3L was run in stock trim using factory timing and fuel curves supplied by a FAST XFI management system. The conservative factory tune certainly limited power production, but the 5.3L pumped out 343 hp and 372 lb-ft of torque. The factory tune minimized total timing and kept the air/fuel ratio on the rich side. After increasing the total timing to an indicated 29 degrees (up from 25) and leaning out the air/fuel mixture, we were rewarded with peak numbers of 363 hp and 385 lb-ft. These are right in line with what could be expected from a good tune on a late-model 5.3L truck. / 053 SUCP MOUSE.indd 53 8/10/11 5:29:22 PM

6 Tech included a new induction system from FAST in the form of the company s 102mm LSXR intake and throttle body. Possibly a tad on the large side for the mild 5.3L, we were still anxious to replace the truck intake to see what would happen. We tried a larger (aftermarket) throttle body on the stock truck intake during testing but saw no power gains at the lower power levels. The stock LS1, LS6, or LS2 intakes might be an affordable alternative to the FAST, but will not likely produce as much maximum power. We may look at the stock intakes in the future, Though cylinder heads abound for the LS engine family, we decided to start things off by shipping our stock heads to the flow experts at Total Engine Airflow. Already considerably better than any production 23-degree small-block head, the 5.3L LM7 heads could be made to flow some serious numbers with proper porting. 054 / SUPER CHEVY /November 2011 SUCP MOUSE.indd 54 8/10/11 5:29:23 PM

7 but Modern Mouse was ready for action after receiving the FAST intake, throttle body, and billet fuel rail. The induction upgrade improved the peak power numbers to 445 hp and 434 lb-ft of torque, but the FAST intake did suffer slightly lower in the rev range. After the upgrades, Modern Mouse was now officially a performance motor, and a good one at that. How do you argue with the combination of smooth idle, a broad torque curve, and 440 hp? Check back with us next month as we cam up, then put the squeeze on Modern Mouse. j Cam swaps on an LS motor are a breeze compared to a conventional small-block. Rotating the cam pushes the lifters up into the plastic guides so it was unnecessary to remove the intake or cylinder heads to perform the cam swap. For our first adventure with Modern Mouse, we chose a mild cam profile. The XFI RPM cam from Comp Cams offered a 0.522/0.529 lift split, a 212/218 duration split, and a wide 114-degree lobe separation angle. Equipped with this cam, the idle vacuum dropped by less than 2 inches while the power output jumped to 385 hp and 412 lb-ft of torque. The mild street cam improved the power output through the entire rev range. 13 The intake ports were given the full treatment to increase the airflow to nearly 300 cfm. That is enough flow to support over 600 hp on the right application. / 055 SUCP MOUSE.indd 55 8/10/11 5:29:23 PM

8 Tech Here Comes Modern Mouse! 14 The exhaust ports were given the same treatment, increasing the flow by nearly 70 cfm The TEA heads also featured a valve spring and retainer upgrade. The double springs allowed us to safely run a cam with as much as lift and rev the motor to 7,000 rpm. Though we would not take advantage of these attributes in part one, look for wilder cam timing in the near future. 17 Equipped with the CNC-ported heads from Total Engine Airflow, the mild 5.3L pumped out 424 hp and 423 lb-ft of torque. The ported heads improved the power output by as much as 40 hp and had plenty of flow left in reserve. 1 Power Numbers Stk Tune Cam Heads Intake RPM HP TQ HP TQ HP TQ HP TQ HP TQ 2, N/A N/A N/A N/A N/A N/A 2, , , , , , , , , , , ,300 N/A N/A N/A N/A Max Equipped with the FAST LSXR induction, Modern Mouse produced 445 hp and 434 lb-ft of torque. The FAST intake shifted the power curve higher in the rev range, but the top-end gains were impressive. The factory LS6 intake would be a low-cost alternative. 056 / SUPER CHEVY /November 2011 SUCP MOUSE.indd 56 8/10/11 5:29:25 PM

9 The combustion chambers are a key element in airflow. The 5.3L heads from Total Engine Airflow also received an increase in intake valve size from 1.89 to 2.0 inches. Cost for the complete set of upgraded heads is $1, The final modification involved the installation of a FAST LSXR induction system, including the 102mm intake, throttle body, and matching billet fuel rails. The factory rails are more than adequate at this power level (we ve run them on motors approaching 1,000 hp). All testing was run with 36-lb FAST injectors, though the factory injectors will work fine at the lower power levels. TEA head flow lift in. ex SOURCES Comp Cams 901/ FAST 877/ Total Engine Airflow 330/ / 057 SUCP MOUSE.indd 57 8/10/11 5:29:25 PM