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"GM High Tech", March 1, 2013





Nothing says hot rodding like dipping into the stock parts bin at GM, mixing and matching OEM components, and coming out the other side with almost 50 extra rear wheel horsepower and OE reliability. This trick, of course, is as old as the internal combustion engine itself, although it’s just recently that a couple hundred dollars worth of GM parts could add this kind of power. Seriously, the package we’re showing of here can be purchased for under 300-bucks if you shop smart (new parts, nothing used) and added 47-rwhp and 20 lb-ft of torque to our bolt-on equipped 2011 Silverado LTZ, through the factory automatic transmission. Besides the healthy power gains, we also drove away with a near stock idle, sublime under-the-curve drivability, long term reliability, and a stop light ready sleeper package that could surprise almost anything you’ll run into on the street. And the best part is, anyone can get this done with a couple hundred bucks and a 6.2-liter LS engine, which means the LS9 camshaft swap will work for a ton of truck guys, and fifth-gen Camaro enthusiasts as well. In fact, AntiVenom recently stuffed a 6.2 in our Ashy Larry project, with the same camshaft, and made over 400-rwhp!

So, what do you need to get this done? Let’s start with the LS9 camshaft (PN 12638427, $166.81), which is borrowed from the Corvette ZR1 and rather similar in specifications to the LS7 camshaft found on the Z06. With 211/230 degrees of duration at .050-inches of valve lift, the LS9 isn’t a tiny camshaft, but it’s also not massive like some of the aftermarket offerings we are accustomed to. Lift is also stout, with .558-inches on the intake lobe and .552-inches on the exhaust side. The smooth idle and tuner friendly drive comes from the large 122.5-degree lobe separation angle, but it is really the entire combo working together that makes this a great bumpstick. Along with the camshaft, would be modifiers will also need a set of LS3 valve springs (PN 12625033, $8.78/each) to handle the high lift, a 3-bolt camshaft gear (PN 12623754, $24.29) to get everything spinning, and an LS3-style front timing cover (PN 12600326, $45.41). If you’re doing this swap on an LS3 Camaro, well, you just need the cam, but truck and L99-equipped automatic Camaros will need all of those parts. Other than that, you’ll just need a weekend of your time and some garage space, or a competent mechanic, to get the job done. For our install, we turned to Greg Lovell at AntiVenom in Seffner, FL and he and his crew had the truck up and running in less than a day. With almost 400-rwhp in a brand new Silverado, it was all smiles in the bay and all tire smoke out on the street.

1 AntiVenom’s 2011 Silverado LTZ test truck had already been upgraded with a K&N intake and a set of long-tube headers prior to our arrival. Those modifications worked well with the stock 6.2-liter VVT-equipped L9H engine as it laid down 348-rwhp and 352 lb-ft of torque during our baseline testing.

2 While it’s not exactly warranty work, the LS9 camshaft swap can be done using all OEM GM parts that can be purchased separately at any GM dealership or as a complete package at AntiVenom. If you’re following along at home you’re going to need an LS9 camshaft (PN 12638427), a set of LS3 valve springs (PN 12625033), an LS3 timing cover (PN 12600326), and a 3-bolt camshaft sprocket (PN 12623754). We’re talking well under 300-bucks for the complete package here...

3 After removing the cold air intake and aesthetic engine covers, Greg jumped right in to the camshaft swap, removing the spark plug wires, coil packs, and the factory harnesses before loosening and removing the valve covers. Once out of the way, Greg pulled the factory rocker arms off and set them aside.

4 One great thing about working on a truck is just how much room there is, and for guys like us who are used to F-bodies and Corvettes, this was a major relief. With the stock belt removed and tossed aside, AntiVenom pulled the radiator hoses off of the water pump outlets and yanked the entire assembly off of the L9H.

5 Newer GM vehicles all feature an annoying “permanent” A/C compressor belt, which has no tensioner and should be cut to be removed... We’re not big on that idea, so Greg likes to carefully pull the balancer away with the belt still in one piece. The installation is a little tricky (good luck), but it saves buying a new belt.

6 With the stock balancer and A/C belt removed, it was time to take the factory L9H timing cover off of the engine. The LS9 camshaft conversion won’t reuse the factory timing cover, since it will no longer use the camshaft phaser or any of the Variable Valve Timing (VVT) system. Make sure you unplug the harnesses and remember the two lower bolts that run through the oil pan.

7 While excellent for fuel economy, OEM drivability, and power under the curve, many enthusiasts don’t necessarily need the variable valve timing found on the L9H and L99 engine family. We’re going to ditch it for the LS9 conversion, but the timing chain will be reused along with the tensioners.

8 Swapping the L9H valve springs for a stiffer set of LS3 units is a good idea, and at under $8 a piece, it doesn’t hurt the wallet either. With the spark plugs removed, Greg fills the cylinders with air pressure, compresses the springs, grabs the stock retainers, and removes the factory springs. The installation is just the opposite...make sure you don’t lose those little retainers!

9 Kyle Miller jumped in to help on the Silverado, draining the radiator, disconnecting the factory transmission cooler lines, and then pulling the beast to make room for the camshaft to come out of the block. The A/C condenser can stay in place, which is a nice touch.

10 Out with the old and in with the new. As always, be careful not to scratch the camshaft bearings or lobes on the way in or on the way out and use plenty of lubrication on the new bumpstick before you slide it in place.

11 The factory camshaft retainer plate gets reused, as do the bolts, but make sure you apply plenty of blue Loctite to these 4 bolts prior to assembling everything. You don’t want that camshaft walking around inside the block.

12 Slide the new 3-bolt timing gear over the camshaft dowel pin and bolt it down using a fresh set of bolts. For our installation, Greg lined the camshaft up dot-to-dot, and left it at that. Note the small tool holding the tensioner off of the chain, which helps get everything in place without a major struggle.

13 Before installing the new LS3-style timing cover, you will need to swap over the camshaft sensor harness. The L9H (above) features a five-pin connector, while the LS3 only uses 3. Swapping the harness over is no big deal, just leave the camshaft phaser plug disconnected and off to the side.

14 Using a GM alignment tool, AntiVenom dropped the LS3 cover over the front of the block and began to tighten everything down. If you don’t have an alignment tool like that one, make sure you get the lower oil pan to timing cover bolts lined up correctly before tightening everything down.

15 The factory rocker arms are more than capable of supporting the LS9 camshaft, and they simply bolt back down over the LS3 springs for a quick and easy swap. Now would be the time to add new spark plugs, if one were so inclined, and tighten down any header bolts that may have came loose over the years.

16 Water pump, belts, hoses, coolant, coils, wires, and a quick once over were all that remained. After that, Greg loaded a new tune file in the ECM, deleted the VVT tables, roughed in new timing and fuel tables, and fired the Silverado up. The idle was, well, stock, as was the throttle response, just what you would expect from a factory camshaft swap.

17 What you may not expect however was the power increase, with the LS9 camshaft picking up tremendous power and torque everywhere. Peak power was up by 47, and torque jumped 20.5 lb-ft. As one would expect, the gains up top were really impressive, with power climbing all the way to 6500, where the factory camshaft tailed of around 5800rpm. The final results were 395.29-rwhp and 372.95 lb-ft of torque.





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