Stroker Engine Build - My First Stroker, Part 2

Camshaft Choice: Black Magic, or Informed Decision?
Choice of camshaft is a critical decision that must be made based on a myriad of factors. These include cylinder bore and stroke, compression ratio, desired usable engine rpm range, cylinder head characteristics, and vehicle drivability concerns. For our cam, we once again looked to Lunati, and it just so happens that the company has a new series of camshafts that brings exciting new technology to the Gen III family of engines. Known as the Voodoo line of cams, these bumpsticks utilize an asymmetrical lobe geometry that up-ramps the lifter quickly and aggressively, yet also more gently re-seats the valve, reducing noise, valvetrain harmonics, and the possibility of eventual component failure. This combination results in a cam that's easy on engine parts yet also yields better throttle response, manifold vacuum, and--most importantly--torque and horsepower.

Or at least that's what the marketing folks told us. We wanted some more technical information on this new line of camshafts before making a final choice, one of the most important decisions to make in an engine build. We called up Lunati's Mark Chacon, the company's East Coast Regional Rep., for the skinny on hydraulic roller camshaft design and the new Voodoo cams' advantages. While not an actual camshaft designer, Mark Chacon is an ideas guy with a reputation for thinking outside the box. He contributed to some engineering direction early in the planning stages of the Voodoo line, and can speak about Lunati's Voodoo camshaft design team (then led by Harold Brookshire) and what it has come up with.

"A lot has changed since Ford produced the first OEM hydraulic roller engine back in 1985", says Chacon. "The original intent was to produce a valvetrain that reduced friction and improved gas mileage. Extra power and torque, though not engineering goals, were gained as an end result of both improved area under the curve over a hydraulic flat-tappet camshaft and reduced rotational friction."Now, fast forward ahead 20 years and camshaft technology has grown to a point where it hardly resembles what it started out as. Major lifter intensities (the duration at 0.020 minus the duration at 0.050) have increased dramatically, more area under the curve has been achieved through better overall lobe designs, and greater lobe lifts are now commonplace. When Lunati first looked at launching a new cam line in the summer of 2004, I was brought in as a consultant to set down some engineering guidelines and to explore emerging technologies. Some of the engineering challenges were to find the perfect balance between quiet valvetrain operation and rpm ability versus excellent torque and horsepower production."He continues, "One problem specific to the LS1 engine is that because of the increased 55mm cam journal diameter, the lobe profile will grow if you use a master that was borrowed from another engine family. This will increase both the velocity and acceleration rates and can cause premature valve float.

Larger-than-stock rocker arm ratios only compound this problem. Looking at all these factors, it became clear early in our engineering that lobes would have to be specifically engineered not only to the engine and cylinder head, but also to the specific journal diameter; and that we'd also need to reverse engineer the lobes to better factor in the added affect of a specific rocker ratio used for the engine.

"That said, the main advantage the Voodoo line has over the designs of other manufacturers is the lifter-diameter-specific masters that will hold as-designed acceleration and velocity rates and also account for the working 1.7 rocker ratio that LS1 engines use. This enabled us to design a cam profile that maximizes both area under the curve and engine rpm without premature valve float. The major lifter intensity that I recommended was 28.5 and our new Voodoo hydraulic rollers are made to this major. The major lifter intensities used by some other hydraulic roller cam manufacturers can be as fast as 25.9, which can create excessive valvetrain noise and could limit the engine's ability to rpm very high. A hydraulic roller lifter, which is heavy compared to other types of lifters, has a hard time effectively working with so much acceleration and velocity without trying to valve float the engine. But with the slightly softer 28.5 major lifter intensity, we are able to get both excellent torque and horsepower numbers while also offering increased rpm and lower valvetrain noise than our competitors' camshafts." He adds, "All Voodoo grinds are designed this way and are ground on state-of-the-art, CNC-automated camshaft grinders for unmatched quality and the tightest manufacturing tolerances in the industry."For our larger-than-stock-displacement and big-flowing-cylinder-head motor, we decided to go with Lunati's most aggressive Voodoo profile available for LS1 engines to date, PN 60512 ($310.00 suggested retail). With 232/238 degrees of duration at 0.050-inch tappet lift (282/288 advertised duration) and 0.599/0.601 inches of lift at the valve, this cam is designed for serious street/strip rides with free-flowing exhaust and intake systems--like ours! The advertised powerband of 2,400-6,800 rpm matched perfectly with our intended engine use, and the cam is said to still exhibit decent street manners as well--important for what is, and will continue to be, a street-driven machine. Lunati also included its PN 72432LUN hydraulic roller lifters, sold separately for a suggested $410.00 (set of 16). These are designed to be used with the factory lifter trays and are made from premium heat-treated steel.

OK, so we got ourselves a sweet hydraulic roller cam, but I started thinking: I've got a solid roller in my TPI Camaro and it works darn good. Am I leaving anything on the table by not opting to 'go solid' in this stroked LS1? "There will always be a horsepower advantage when using a solid roller camshaft over a hydraulic roller camshaft," says Chacon. "But there are also some drawbacks when using a solid roller camshaft in a street environment. The Voodoo cams close the gap between conventional hydraulic roller cams and solid roller camshafts. If revs are the name of the game and the intended rpm will be above 7,500 rpm, then I would use a solid roller camshaft because the lifter will continue to remain stable at these higher rpms. But in a good street/strip application that will operate at 7,200 rpm or below, I would use a hydraulic roller because the overall long-range drivability and lack of maintenance is much better suited for a good street/strip application." Given the daily driven nature of this Trans Am, Mark really put my mind at ease.

The front cover, rear cover, and oil pan gaskets, along with the front and rear crankshaft oil seals, are just a few of the high-tech sealing devices used in the LS1.

GM Gen III Gasket Technology
The gaskets used to seal the various mating surfaces in the LS1 engine merit a closer look, as they are extremely advanced pieces indeed. Though very high-tech and durable, when performing a full engine rebuild, it's an excellent idea to replace them as per the GM service manual. Though this will require the expenditure of a little extra cash on your stroker build, it'll guarantee a leak-free motor when you're through.

Unlike previous-generation small-blocks, the Gen III does not rely on cork- or fiber-based gaskets and large amounts of RTV silicone to form seals. Anyone who has ever assembled one of these older-style engines knows that this approach results in, for lack of a better term, a friggin' mess. Instead, the major gaskets in the Gen III are carrier-type (more technically, controlled compression aluminum carrier gaskets). The hybrid design means that when sealing surfaces are tightened together, the aluminum portion of the gasket limits how far the silicone portion of the gasket can be compressed. This results in a more reliable, longer-lasting seal and less chance of fastener overtorquing. In addition, the aluminum portion of the gaskets prevents the gasket relaxation associated with traditional materials and also allows them to become structural parts of the engine.

You can see this carrier design primarily in the front and rear cover, oil pan, and valley cover gaskets. Perhaps best of all from the perspective of the do-it-yourselfer, there's no scraping needed when these gaskets are removed for service; and if they don't have many miles on them, they can even be reused. But again, since we're doing a full engine overhaul on a motor that has seen tens of thousands of miles of use, we're replacing everything we can just to be safe.There's a lot more to say on this topic, and we don't have the space to go through the technology that goes into each and every gasket and seal used in the Gen III (you can see more bits and pieces in the photo captions). But now that you've gotten a feel for the kind of careful design and manufacturing that goes into them, hopefully you'll take our advice and spring for fresh gaskets and seals throughout the engine.