100 Horsepower Anybody Can Install in Gen 3 LS Engines

The engine assembled here with SLP components was evaluated on a dynamometer before being installed back in a vehicle to verify the performance increase. You don’t need a dyno to feel an extra 100 hp — it’s dramatic! This engine was assembled and dyno tested at Wheel to Wheel Powertrain (248/589- 1190 www.wheeltowheelinc.com). The dyno results listed later in this chapter tell the potential of the Gen III and the effectiveness of these parts. Going from 370 hp to 470 hp (standard correction) without touching the short block is very impressive. As you probably can tell, these are dyno headers, used so Wheel to Wheel could record exhaust gas temperatures across all the cylinders.

The components used for this upgrade come from SLP (www.slponline.com). The SLP components used here include assembled CNC-ported cylinder heads, a special roller camshaft, LS6-style intake, roller timing chain, 160-degree thermostat, MAF sensor, cold-air box for the vehicle, various single-use gaskets and fasteners, along with longtube exhaust headers (a few components not shown). All the aluminum- reinforced gaskets and seals required in the process of replacing these hard parts are available from GM or SLP. Also, SLP offers a calibration to go with these components. It needs to be flashed into the vehicle’s PCM to take full advantage of the potential of this package.

1. The LS-1 V-8 engine has very few hoses on its exterior, but the few that are left once an engine is removed from a vehicle will need to be pulled off the intake. This Gen III V-8 is an ’01 LS1, but the entire Gen III engine family is similar except for a few hoses, wires, and sensors, so most of this info will apply to any Gen III V-8. You can easily remove these PCV hoses that connect the valve covers by pulling them off the valve cover vent tubes by hand.

2. On the LS1 and LS6 intakes, the throttle body is connected to the cooling system by a water hose, which heats the body for improved start-up performance. To remove the hose, use pliers to release the clamp and a screwdriver to work the hose off the tube, or you can use one of these cool clamp/hose pullers from Snap-On.

3. The LS1/LS6 low-profile intake manifold is held in place with ten 6- mm diameter bolts with 8-mm hexheads that go into the block. The bolt holes in the block are open to the crankcase, so you need to use some thread sealer when you reinstall them (they come with sealer on them from GM, but they’ll need a reapplication the second time around). Once these are loosened, it’s easy to pry off the O-ringed intake with a screwdriver.

4. The Gen III V-8 has two knock sensors that bolt to the block deep inside their “nests” in the intake valley cover plate. You need to remove the wiring connectors to prevent the wiring harness from being damaged in the process of tearing down the engine. The first step is to gently pry the rubber grommet loose using two screwdrivers, as shown.

5. There’s a special tool available to remove the knock sensor wiring connector from the sensor bolted to the block, but the pros at Wheel to Wheel Powertrain have figured out how to remove the connector using two screwdrivers. By pinching the connectors at the widest point of their base, the two retaining tabs that hold them are relaxed and the connector can be removed from the sensor.

6. Early Gen III V-8s came with this tubing apparatus to vent any steam pockets in the cooling system from both the front and rear. The LS6 intake (which became standard on both the LS1 and LS6 in 2002 and beyond) has more drop in it for a larger plenum area, so GM eliminated the tubing under the intake. To make this work, the rear vent holes are blocked off and the front steam vents are tied together with a tube (the front ties into the throttle preheat system). To remove the vent tubing, loosen the four 6-mm bolts with a 10-mm hexhead socket.

7. Be careful not to lose these steam vent tubing seal plates — often they stick to the engine and appear to be part of the block. If you lose them, the steam vent mounting blocks won’t seal against the engine block.

8. Each spark plug on the Gen III has its own coil, with four coils mounted on each valve cover. GM has used two methods to mount the coils to the valve covers. One system, shown here, has the coils mounted on a single bracket. In the other method, used from 1997 to 1998, the coils are mounted separately to the valve cover (these valve covers have perimeter bolts on the valve covers unlike later versions that have the four bolts down the center of the valve cover). To remove the bracket-mounted coils, you’ll need to remove the 6-mm diameter bolts with a 8-mm hex-head socket.

9. The valve covers are a dead giveaway to how old the engine/heads are — the perimeter-bolt valve covers were built from 1997 to 1998, and the center-bolt valve covers were built from 1999 to present.

10. The rocker assembly on the Gen III is ingenious in how easy it is to install/remove. Simply loosen the 8- mm diameter bolts with an 8-mm hexhead and the entire system lifts off as a unit. If you are running a CNC-ported head, a good idea is to put sealer on the rocker anchor bolts that are above the intake ports, as the porting process usually removes a lump of material in the intake port that exposes the bottom of these bolt holes.

11. Now you can remove each of the pushrods. If there is one part that always needs to be upgraded for performance applications in the Gen III, it’s the pushrods. Buy good replacements and sleep easier.

12. There are ten 11-mm diameter bolts with a 15-mm hex head (on the ‘97-03 engines, there are 2 short bolts and 8 long bolts per cylinder head; the ’04 blocks use all short bolts) to clear the water passages in the block at each end of the cylinder head that hold each Gen III cylinder head on the block. There are also 5 M8 bolts with 10-mm hex heads to seal the intake port area. These bolts are not to be reused! They are a torque-to-yield design. The bolts are torqued to 22 ft-lbs, a torque that is minimally affected by the variations in friction from the type of lubricant used on the fastener threads or mating surface of the bolt head to cylinder head boss. Then, a torque angle gauge is placed on the wrench and the fastener is twisted to a predetermined angle.

13. The harmonic balancer is also the crankshaft pulley, which eliminates one step of the disassembly process. If you use a deep-throat puller, don’t let the center push bolt of the puller seat in the end of the crank, as it will probably damage the threads in the crank. Instead, you can use a big socket or an adapter for the puller to seat against. When reinstalling the harmonic balancer, make sure to torque the bolt to 37 ft-lbs and twist it 140 degrees.

14. There are ten 10-mm hex-head, 8- mm diameter bolts to be removed from the main portion of the oil pan, and two 10-mm hex-head, 6-mm diameter bolts at each end of the oil pan that bolt to the front and rear covers. You need to remove them all to get the oil pan off the engine. The oil pan is a stressed member on the Gen III V-8, but it doesn’t use dowel pins or any other type of locator, so the installation process requires some detail to get the front and rear covers and oil pan to all find their homes.

15. The front cover is removed after the water pump is removed (six 8-mmdiameter, 10-mm hex-headed bolts). The front cover is held in place with eight bolts that have a 10-mm hex head and an 8-mm diameter. You’ll probably need to use a little coercion to free the cover from the block. Do not reuse this seal; it’s a compression design that can only be used once. The rear cover is pressurized, so it’s held on the engine with more 8-mm diameter, 10-mm hex-head bolts — 12 to be exact. The front, rear, and top cover, along with the oil pan, all use the same length 8-mm-diameter bolts.

16. When you’re increasing power production on the Gen III, it’s important to increase the oil flow and pressure in the engine. You can do this by adding a stiffer bypass spring and/or porting the outlet of the oil pump. Either way, the oil pump pickup tube will need to be removed. Once the oil pan is off, remove the one 6-mm diameter bolt with a 10-mm hex head at the bottom of the oil pump. You’ll also need to remove the one 8-mmdiameter stud (not shown), which has a 13-mm hex-head nut that holds the oil pump tube tab at the bottom of the engine. Removing both of these will release the pickup tube.

17. The Gen III has its oil pump driven off the front of the crankshaft, which becomes obvious after the cam cover/water pump front cover is removed. Taking the four 8-mmdiameter, 10-mm hex-head bolts off frees the oil pump for rework. Reinstalling the oil pump requires centering the bare oil pump body on the crank. This is done by installing four bolts to 45 in-lbs and centering the pump with two 0.002-inch feeler gauges.

18. The cam gear is held in place with three 8-mm-diameter, 10-mm hexhead bolts; and don’t worry, it self centers.

19. All Gen IIIs have roller cams, which means the cam must be retained on both ends (unlike cams with flat-tappet lifters, which hold the cam in place by the spinning of the lobes). Under the cam gear is the cam plate, which is held in place with four 8-mm-diameter, 10-mm hex-head bolts. When you’re reinstalling these bolts, they should have a few drops of blue Loctite placed on the threads before they’re torqued to 18 ft-lbs.

20. Probably one of the most ingenious aspects of the Gen III is that spinning the camshaft one revolution with the upper valvetrain removed pushes all the lifters up into their retainers and allows the cam to be removed — with the lifters still in the engine. The lifters won’t stay in the retainers forever, so install the new cam sooner than later. The cam is hollow, so W2W slides a 6-inch-long, 3/8- inch socket extension in the hollow portion of the cam to lift and pull it out of the block a little. Then, once it’s far enough out of the block to grab, they pull it out like this. Once the cam is out, you’ll have torn down the top end of a Gen III V-8 engine. Now you can add the components to easily make over 450 streetable horsepower.

21. When increasing the power on a Gen III V-8, the oil pressure/flow needs to be increased to ensure there is sufficient oil for lubrication and cooling. To address this, disassemble the oil pump to modify it for increased oiling. Unbolt the seven 6-mmdiameter, 10-mm hex-head bolts, remove the cover plate, and slide out the gerotor gears. Mildly radius the inlet and outlet of the pump body with a grinder and clean it thoroughly. Once the body is reinstalled properly on the crank, lube all the parts liberally with engine oil before reassembling the pump body.

22. SLP provides a shim to place inside the oil pump pressure bleed-off spring bore to increase the line pressure in the oiling system. Here, the shim is being pushed into the bore of the oil pump pop-off spring. Install the spring and shim by first releasing the factory pop-off spring. Remove the threaded 8-mm Allen plug on the side of the oil pump body. Then, slide the shim inside the bore, apply a few drops of red thread locker on the threads of the Allen plug, and reinstall it in the pump body.

23. The SLP camshaft is a 234/228- degree grind with 0.576/0.571-inch lift on the intake/exhaust valves. This is all on a 112-degree centerline with 113 degrees of lobe separation. If you don’t speak camshaft, this means the cam is a street-grind roller lifter cam that’ll work with the stock hydraulic lifters, provide a slightly lopey idle, and will make good power across the RPM band, yet still be acceptable to drive every day. The cam journals should be lubed with standard 30-weight engine oil. The lobes should receive a good slathering of the SLP-provided lobe lube. Apply a thorough coating here to ensure a smooth startup. As a note, roller cams don’t need high-performance moly-based lube at startup, especially since the moly ends up everywhere inside the engine.

24. While this pump is shown being reassembled on the bench, the oil pump needs to be centered on the crank before being reassembled. When that is done, reassemble the pump body and bolt on the front plate. The 8-mm bolts that hold the oil pump front plate in place need two drops of blue Loctite to minimize the chance of them coming loose in the future. Torque them to 106 in-lbs.

25. The best way to install the hollow cam the final third of the way is with a long 3/8-inch-drive extension slid up inside the cam. This provides leverage as the cam is negotiated past the last few cam journals in the block. Up until that point, the cam can be installed by hand, as shown.

26. Reinstall the Gen III V-8 cam cover plate at the front. The four 8-mm fasteners on the front plate should receive two drops of blue Loctite before being torqued in place at 18 ft-lbs.

27. The Gen III V-8 comes from the factory with a roller timing chain, but it’s recommended that you use a more robust performance timing chain, as the stockers have been known to fail in hi-po applications. Luckily, SLP offers a stout roller timing chain and gear combo that bolts in place of the stock unit with no modifications.

28. Apply a few drops of engine oil to the crank snout and place the bare oil pump body over the snout of the crank (this oil pump will be disassembled in the next step). The four 8-mm fasteners will need a drop or two of blue Loctite on them before they’re finally torqued to the 18 ft-lbs, but don’t do that yet. To align the pump body to the crank, attach the disassembled pump body on the engine with two fasteners torqued to an initial force of 45 in-lbs. This low torque level will allow you to center the pump body on the crank to avoid uneven wear in the pump.

29. GM sells a special tool to center the oil pump, but there’s an easy way to get this done without buying the tool. Slide two 0.002-inch-thick feeler gauges far enough into the pump so they are between the pump body and crank snout 180 degrees apart. Sweep the feeler gauges around the snout diameter — this will center the oil pump on the crank snout — while keeping them 180 degrees apart. With the feeler gauges still in place, apply two drops of red Loctite to the uninstalled bolts and torque them to 18 ftlbs to lock the pump in place. Now, remove the initial torqued bolts, apply Loctite, and reinstall at 18 ft-lbs.

30. Once you bolt the oil pump back into place, you can reinstall the oil pump pickup. Apply a light coat of lube to the o-ring before installing. then, use some red Loctite and torque the 8-mm fasteners on the oil pump to 18 ft-lbs and the 6-mm nut on the center main stud to 106 in-lbs.

31. Install the new front cover gasket loosely and then install the harmonic balancer to center the cover around the crank. GM designed the Gen III LS1 V-8 so many of the components find their own home, which means it has few external locators. Then, snug the fasteners on the cover to 89 in-lbs in a radial sequence, and finish by torquing them in a radial sequence to 18 ft-lbs to get everything properly located. See Illustration 32 for details on checking alignment before finaltorquing the cover fasteners.

32. While the front and rear covers on the Gen III V8 essentially “self-locate”, this illustration shows how to measure the exact tolerances the GM manufacturing process recommends. (Illustration courtesy of GM)

33. The Gen III V-8 was designed to have only planar mating surfaces. This means there aren’t angular mating points, which can lead to oil leaks — like the common leak point for small-block Chevys where the oil pan seal arc meets the block rail. While the use of liquid sealer is rare on this engine, it is needed where the front and rear covers mate with the engine block and oil pan. Put four approximately 3/8-inch dollops of sealer at the four corners and then install the oil pan. (Illustration courtesy of GM)

34. The oil pan is then installed on the engine block with the fasteners handtightened in place to help locate it. The oil pan needs to be aligned before final torquing. To do this, the two long 6-mm fasteners at the rear corner of the oil pan that thread into the rear cover are torqued to 9 ft-lbs. The oil pan is a stressed member in the powertrain, so the back surface of the pan needs to be aligned with the rear face of the rear cover. The two surfaces need to be aligned within 0.020 inch (0.500 mm), with the oil pan always forward of the rear face of the cover. Now final-torque the twelve 8-mm bolts to 18 ft-lbs in a radial pattern.

35. There are two different head gaskets used on the Gen III V-8. The 1997- ’98 Gen IIIs used a head gasket that can be used on all Gen IIIs, but many hot-rodders believe it cannot withstand the same abuse as the 1999- and-later head gasket. The early head gasket can be identified because it has a cutout at the lower edge between 1 and 3 or 5 and 7 (depending on what bank you’re talking about) on the lower edge. An important caveat here is the later head gasket cannot be used on the 1997-’98 head. Using this later gasket on older Gen IIIs will result in a substantial water leak — so make sure you get the right head gasket for your application.

36. This is critical! Blow out all the head bolt holes with pressurized air to make sure no incompressible fluid (oil, water, coolant, etc.) is in them. You will crack the block if you torque down the fasteners with any incompressible fluid inside — making the block junk. Cover the bores to keep any fluid from landing in them when you blow out the holes.

37. Take a few minutes to make sure the engine block and cylinder head mating surfaces are free of anything that might prevent a tight seal between them. A good way to do this is to scrape the head surface with a razor blade. Suck the debris away using a vacuum cleaner tube placed close by.

38. The SLP CNC heads install just like the stock heads, but it’s probably not a bad idea to check valve-to-piston clearance with some clay on the dome of one of the pistons to make sure the cam/head change hasn’t put you in the danger zone. Put about a 1/2-inch dollop of modeling clay (don’t use Playdoh, as it will spring back and give you a false reading!) on the intake and exhaust valve head, bolt the cylinder head on with the old head gasket and four head bolts, cycle the valvetrain through one revolution. You must use either a solid lifter or a checking valvespring so the lifter doesn’t collapse and give you a false reading. Remove the head and measure the depth of the clay by plunging a micrometer through the thinnest portion. It should be more than 0.120 inch on the exhaust valve and 0.090 inch in the intake, or you’ll need to add valve reliefs in the pistons.

39. Here’s where power is made. The Gen III V-8 “cathedral” intake ports are highly refined from the factory, but they do respond to specific porting work. While port development is still a black art, the act of creating CNC ports is a science. Once a port shape has been created, the CNC machines can duplicate them with impressive accuracy at a reasonable cost. There are many sources for CNC-ported cylinder heads.

40. Many of the critical fasteners, like the head bolts, on the Gen III V-8 use bolt stretch instead of torque to make sure they have the proper clamping load. To help minimize bolt stretch variation, it’s recommended you apply lube to the backside of the fasteners as is being done here. Do not apply any lube, thread sealer, or thread lock to the threads of the 11-mm head bolt fasteners.

41. The process of setting the proper clamping load on the head bolts goes like this. All of the new 11-mm head bolts are torqued to 22 ft-lbs (30 N-m) in the factory recommended sequence (1 through 10). Using a Sharpie pen, apply a vertical line to all the head bolts to use as a reference when applying the twist to the bolts. Then, install the bolt torque angle meter tool (GM PN J36660 or Snap-On PN TA- 360) on a breaker bar and add 76 degrees of rotation to each bolt — again in the factory recommended sequence. Add another 76 degrees of rotation to the long bolts (1 thru 8), while the two short bolts per head get only 34 more degrees rotation (bolts 9 and 10). Torque the top five 8-mm bolts to 22 ft-lbs beginning with the center bolt (bolts 11 thru 15).

42. Install the LS6 intake manifold with new gaskets (available from GM, SLP, and other parts houses). This brings up a good point: don’t reuse any Gen III V-8 gaskets because they are all of the compression-carrier design. This means the aluminum surface of the gasket takes the torquing load to control how much compression the embedded silicon sealing surfaces experience. This maximizes sealing control and minimizes the need for retorquing to maintain the clamping load – but they are one-use items.

43. The lightweight intake is made of nylon, so it does not require a lot of torque to lock it in place. Many of the intake bolts are exposed at the bottom of the threaded hole, so apply thread sealer/lock to all of their threads. Make a first pass on the fasteners at 44 in-lbs following this sequence. Make a second pass over the fasteners to come to the final torque of 89 in-lbs.

With the addition of a few hot-rod parts, the power improvement to the LS1 is very real. Most of the additional power comes from upgrading to the latest performance components that let the engine breathe.