In the February '08 issue of Super Chevy ("Totally Exhausted") we began our quest to gain or exceed Z06 power output from a stock LS1 with just bolt-ons. After the flawless installation of a complete SLP exhaust system and some tuning, our '99 Corvette test vehicle pumped out 338 hp and 348 lb-ft of torque at the wheels, which resulted in a gain of 25 hp and 24 lb-ft of torque. With an estimated 398 engine horsepower, we were only seven ponies shy of gaining factory-rated Z06 power.
What to do next? After putting in a call to Dr. Jamie Meyer at GM Performance Parts, we decided to bolt on a set of GMPP's LS6 CNC-ported cylinder heads (part #88958665) and LS1 Hot Cam (Part #1248003). In order to install these components atop our LS1, we would have to change the intake manifold over to an LS6-styled unit (part #88894339). Once again, what were our options? We had plenty, but we decided to stick with components from within the GM family. By keeping with the General's front line, we were damn near guaranteed a proper fit, ease of installation, and excellent power gains with total streetability.
Shown here is the LS6 CNC-ported...
Shown here is the LS6 CNC-ported aluminum cylinder head as received from GMPP. These cylinder heads have received the same CNC-port job as the LS6 race-only cylinder heads, the only difference being that the units we are installing maintain a 65cc chamber-resulting in a pump-gas friendly 10.5:1 compression ratio. The LS1 head has a noticeable hump (slowing flow) within the intake port, while the LS6 unit has a more direct, smoother design.
In order to keep with the program we called upon Mike Morgan, Parts Manager at Lattof Chevrolet in Arlington Heights, Illinois, for our incidentals such as cylinder head gaskets, cylinder head bolts, valve cover gaskets, exhaust header gaskets, timing cover and water pump gaskets-all of which were GM production style components. Lattof Chevrolet has been in business since 1936 and selling GM Performance Parts for approximately 15 of those years. Whether you need something small like a gasket or something as large as a crate engine, Lattof can provide.
After filling the hatch of our C5 with the aforementioned products, we headed south to South Amboy, New Jersey, to visit Crazy Horse Racing-a well-known shop within the Ford racing world. Following a recent discussion with Chris Winter (owner of Crazy Horse), we were pleased to hear that he would be entering the Chevrolet fray as well. What better way to kick it off than with our '99 Corvette project car.
Let's get it on!
ConclusionNeedless to say, we were extremely happy with the results of this two-part project-the Dynojet read 411 hp and 385 lb-ft of torque-that's a gain of almost 100 hp and 62 lb-ft of torque from our initial baseline of 312hp and 323 lb-ft. Estimated flywheel horsepower checks in at approximately 475 hp, which is 70 more horsepower than the C5 Z06 ... something we'd like to call total annihilation. Due to impeding deadlines and bad weather we were unable to get the C5 to the strip for some after numbers, but we figure we should see times in the 11.90s on the street tires, at around 115 mph.
That being said, with a little over $5,000 in parts for both installations on the project, we've turned out a C5 Vette that will slaughter just about any Z06 it encounters.
 In order to be sure we have...  In order to be sure we have the best comparison possible, Chris Winter performed a couple of baseline dyno pulls, as results can vary slightly from shop to shop. The C5 pumped out 333 hp and 343 lb-ft of torque on the Crazy Horse Dynojet, only five points shy of those on SLP's Superflo dyno. Technician Glen Knell was chosen to perform the work on the Vette. Glen has Bow Tie blood running through his veins, which dates back to his grandfather. Glen first removed both front wheels and unfastened both outer tie-rod ends. Why the tie-rod ends you ask? The steering rack is directly in front of the harmonic damper, which will require removal to gain access to the camshaft. |  Next, we removed the air filter/mass...  Next, we removed the air filter/mass air sensor assembly as a unit. Beyond that, the radiator was drained and the shroud was removed. In order to gain better access to the front of the engine, the radiator hoses and radiator were removed from the vehicle. The radiator is mainly harnessed by the upper radiator support and fastened by 10mm bolts. The air conditioning condenser can stay in the vehicle and was swung towards the nose. |  Once we gained better access...  Once we gained better access to the front engine compartment, Glen removed the two power-steering lines (pressure and return) and the two mounting bolts that fasten the steering rack into the cradle. For some additional clearance the four subframe bolts were loosened and the steering rack was carefully removed through the driver side-wheel opening. Next we removed the bolt holding the damper to the crankshaft. |
 Using a 10mm socket, we began...  Using a 10mm socket, we began to remove the fasteners that hold the intake manifold to the cylinder head. After removing all of the necessary wiring harness connectors for the fuel injectors, MAP sensor, throttle body DBW, and removing the fuel feed line from the fuel rail, Glen removed the intake from the engine. |  Next, we removed the ignition...  Next, we removed the ignition cables and coil pack assemblies from atop the valve covers. You guessed it-we then removed the valve covers along with unfastening the headers and laying them to the side. |  Back on the front of the engine...  Back on the front of the engine we removed the alternator and bracket as an assembly, as well as the water pump assembly. This would allow access to the timing cover. In order to remove the power steering pump we needed to use this puller as the pulley is pressed on. |
 Now that the heads have been...  Now that the heads have been removed, we were able to remove the lifters from the lifter bores. The plastic housing shown helps retain the roller lifter true within the bore. Once the lifters are removed the camshaft can now be taken out of the block. Next, Glen employed this dual jaw puller from Snap-on Tools in order to remove the damper from the crankshaft. |  Using a 10mm socket, we proceeded...  Using a 10mm socket, we proceeded by removing the rocker arms as an assembly, followed by the pushrods. Once the rockers were removed, the fasteners that hold the cylinder head to the engine block were removed. The cylinder heads were lifted from the engine. |  Once the damper was out of...  Once the damper was out of the way, Glen removed the timing cover and the camshaft sprocket, which is held in with three bolts. Be sure to line up marks on the upper and lower sprocket before removal to avoid extreme valve damage. The next step was to remove the fasteners for the camshaft retainer plate. The camshaft can now be carefully removed from the block. Caution must be used not to snag any camshaft bearings from inside the block. |
 After applying a liberal amount...  After applying a liberal amount of camshaft assembly lube, Glen carefully installs our new LS1 "Hot" camshaft into the block. This particular camshaft checks in at .525/.525-inch lift and 218/227 of duration @ .050 inch. Once all of the timing components are reinstalled and torqued, the timing cover is reinstalled using a new gasket. Be sure to dab some silicone in the lower corners near the oil pan to keep from having an oil leak. |  Not wanting to be repetitious,...  Not wanting to be repetitious, all components are reinstalled in the reverse order. The cylinder heads must be torqued in sequence to 22 lb-ft (on the 15mm bolts), and 90 twice (equaling 18). The smaller 10mm bolts get torqued in sequence to 22 lb-ft. These specifications are for stock-style bolts; aftermarket bolts may require different procedures. Be sure to thoroughly clean all bolts holes and the cylinder head surface before head installation. The LS1 "Hot" cam also required a valve spring change. The valve springs come with the camshaft and can be easily changed with this nifty valve spring compressor tool from Snap-on Tools. Be sure to have a magnet available to remove the keepers from the retainers. Installed height measured 1.80 inches, which was as specified. |  As we tried to install the...  As we tried to install the LS6 intake manifold we ran into a clearance issue. The coolant tubes that run across the valley needed to be altered. Tubes could have been purchased for a 2001-and-up Corvette. However, because time was of the essence, Glen cut and fabricated the current ones for use. The front was welded (as shown), the rear was cut and a high-pressure hose was employed to carry coolant from fitting-to-fitting. |