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6.0 Gen III Engine Block - Stump Puller
Transforming the Gen III 6.0L Into a Big-Inch 402
Henry De Los Santos
Nov 13, 2006
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6.0 Gen III Engine Block - Stump Puller
The key to bigger cubes is utilizing a longer-stroke crankshaft. The factory Gen III 6.0L truck block employed a 3.622-inch stroke crank with its 4.00-inch bore to produce 364ci. To create the additional 38 inches to make our 402ci small-block, we used a 4.00-inch-stroke 4340 forged-steel crankshaft from Eagle Specialty, which is internally balanced and comes with the reluctor ring already assembled.
Our slugs of choice for this build were Probe Industries Sportsman Race Series (SRS) LS1 pistons (also available in the factory Performance Series) with the top and second ring gaps set at 0.023 inch. It's important to note these newly created LS1-specific pistons are carved out of a 2618 T6 aluminum alloy and designed to be used with aftermarket rods and stroker crankshafts. Depending on your particular application, Probe offers them as a flat-top or with a dish strong enough to handle everything you can throw at it-including healthy doses of nitrous and heavily boosted applications.
Complementing the crank is a set of Eagle's ESP 6.125-inch-length H-beam rods, which feature a 4340 steel forging, 0.927-inch wristpins, and ARP bolts.
Eagle also gives you the option of upgrading to a set of either ARP 2000 or ARP L19 rod bolts.
It's in the Air Flow
For unparalleled performance, SLP/AFR 225s are a tough act to follow with their incredible flow characteristics in both the low- and mid-lift range. And while these heads are well suited for bigger-cubic-inch motors like ours, they will certainly cater to small-inch motors that are built more so on the radical side. Add in the 3/4-inch-thick head deck, reinforced rocker-stud bosses, thick wall runners, and choice of 65cc and 72cc configurations, and you have one outstanding piece, which can easily be used in conjunction with big power adders. Best of all, they come with an emissions order (D250-4), making them smog-legal in all 50 states.
Motivating the valves is a SLP hydraulic roller that specs out at 250/246 duration at 0.050 and 0.596/ 0.596-inch intake/exhaust lift on a 114-degree lobe displacement angle.
At the core of our build is a new 6.0L cast-iron truck block ordered right out of the GM Performance Parts catalog. With the crank in place, we added a complete set of ARP main studs for added structural rigidity.
With the crank in place, the inner main cap studs were torqued to 60 ft-lb with moly-lube, the outer cap studs to 50 ft-lb with moly-lube.
Completing our bottom-end build, the factory cross-bolts were torqued to 19 ft-lb.
After carefully positioning the pistons and rods through the cylinders, the rods were then torqued to 63 ft-lb with moly-lube. Once assembled, the final crank endplay measured in at 0.004 inch.
Up front we used SLP's heavy-duty timing chain to ensure accurate timing, for its enhanced strength, and because it allows for easy timing adjustments up to 8 degrees.
Another SLP item is the high-volume oil pump. These oil pumps are blueprinted to exact GM specs, feature a ported inlet and outlet for cooler oil temperatures, and reduce power-robbing oil shear. Along with the pump, you get a heavier spring for higher oil pressure levels along with two styles of O-rings for varying oil pick-ups-definitely a must- buy item for any high-performance Gen III build-up.
With the new oil pump in place, Dennis torqued the factory windage tray to 28 ft-lb and mounted
Up top, a set of CNC-ported SLP/AFR 225s with 72cc combustion chambers and 2.08-inch intake and 1.60-inch exhaust valves were used to maximize the big-inch mule. Since we didn't want to deviate from a pump-gas street motor, a set of thick 0.055-inch Fel-Pro MLS gaskets were used to keep the compression relatively mild at 10.4:1. Securing the heads is a complete set of ARP studs that were ultimately torqued to 70 ft-lb, while the five smaller top studs were torqued to 14 ft-lb. Lastly, the knock sensor and valley pan were locked into place.
No trick pieces here. We used a set of factory hydraulic lifters along with the plastic retainer tray supplied by Turn Key Engine Supply.
Before installing the oil pan, including the front and rear cover, be sure all holes have been attended to and all sensors have been properly placed. Especially crucial are the two oil plugs that need to be placed at the rear of the motor to correctly divert the oil to their respective passages.
Keeping the valvetrain in check is a set of COMP Cams Pro Magnum 1.75:1 roller rockers along with a set of 7.450-inch-length (0.080-inch-wall) chrome-moly pushrods on the intake/exhaust.
Induction chores were handled through an Edelbrock's LS1 dual-plane manifold. As an added bonus, Edelbrock followed the OEM's route and uses the factory O-rings as opposed to paper gaskets, making it that much easier to install. In our case, we simply swapped them over from our old manifold.
Don't overtighten the bolts! Our best advice is to keep an eye on how the O-ring compresses, and once fully compressed, give them a quick snug and that'll do it.
We initially topped off the Edelbrock manifold with Demon Carburetion's 750-cfm Mighty Demon carburetor, but later discovered that we could take advantage of a larger 850-cfm version for added gains.
Adding Wilson Manifolds' 1-inch open spacer further increased our performance gains by 4 hp.
Igniting the fire is a set of MSD replacement LS1/LS6 Blaster Coils. The new coils are designed to work with the factory electronics while being able to produce their patented multiple-spark discharge. Expect to see a controller in the near future that will enable you to program various functions of the ignition. Trust us; it'll be one trick item you'll want to learn more about!
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