We've heard the news, tested the parts, and now we believe in the power of Voodoo. The engine experts and camshaft engineers at Lunati have devised a new and improved profile capable of building more torque and horsepower while keeping the budget as low as possible.
We were curious as to how much of a power increase a street/strip Voodoo cam would afford as compared to a stock replacement camshaft. We contacted the experts at SA Engine Design for the best blueprint. Their combination included a Hye Tech Performance 350ci short-block with GM Performance Parts Bowtie Vortec heads (180cc intake runners), a Professional Products Cross-Wind intake manifold, and a 750cfm four-barrel Holley carburetor. The parts swap was easy and the results were gratifying as we increased peak power by 60 hp and torque by 13 lb-ft.
Changing a camshaft is simple if you have some help in the confusing corners. We did our cam swap in about an hour on a chassis dyno, using air tools; an in-car installation with hand tools takes a bit more time. The first step requires removing and labeling anything in front of the timing-chain cover and on top of the intake manifold. Once the coolant is drained and the accessories are out of the way, remove the intake-manifold bolts. A small hammer and chisel or flat-head screwdriver may be needed to pry the intake manifold from the engine block. The cork or silicone gasket material in this area will be replaced so damage is not a concern. After removing the intake manifold, scrape the front and rear block rails clean of cork, silicone, oil, or any other foreign substance. Line the lifter valley with paper towels to capture the debris.
Remove the valve covers to access the rockers, pushrods, and lifters. Keep the rockers and pushrods in order. While you remove the rocker nuts, the engine may have to be turned over a few times in order to take valvespring pressure away from certain rocker-to-valve stem contact points.
The timing cover is one of the most difficult parts of an in-car installation. The oil pan must be lowered enough to remove the timing cover while also clearancing the crankshaft snout. With the cover off the engine, remove the three upper timing-chain bolts, along with the lower timing gear if a new timing chain is to be installed. A fresh chain provides cheap insurance; a "seasoned" chain has a tendency to stretch and can alter timing by as much as 2 degrees. Lunati offers a high-performance double roller chain that prevents stretch and is a lot less likely to break or skip a gear tooth that would otherwise destroy the entire valvetrain. After changing the upper and lower timing gears, remove the stock camshaft.
Though using a camshaft removal tool is ideal, if the budget is tight you can work the cam out of the engine block by twisting it slowly and carefully, taking precaution not to scratch or gall the bearings. Clean and lube the new cam before installation. Move it as far back as the plug at the rear of the block will allow, and fasten the upper timing gear. Once the camshaft's timing-gear bolts are secure, it's time to set the valve timing. Begin by making sure that the upper timing gear has the manufacturer's pre-marked timing dot at the 6 o'clock position. Then, in a linear sequence with the upper timing-gear dot, rotate the crankshaft until the same dot or equivalent marking on the lower timing gear is at 12 o'clock. This sets the engine's rotating assembly at Top Dead Center (TDC) and its timing at 0 degrees of rotational advance.
We use the term "equivalent marking" because some high-performance chains offer different degrees of advance or retard for specific applications. These markings are visible on crankshaft gear and tell the engine builder at what degree of rotation the crankshaft will be set at when the camshaft is installed. Most Voodoo cams have timing advance pre-ground into the camshaft and require the installer to set the cam and crank gears in sequence with one another (see manufacturer's recommendation). With the camshaft in place, the upper timing gear should have its timing dot in the 6 o'clock position; the lower timing gear should show its zero-degree marking in the 12 o'clock position. Checking this will ensure proper valvetrain movement and allow the engine to respond the way the camshaft intends it to.
Once the timing chain is in place, take the utmost care in positioning the lower portion of the timing cover over the oil pan to make sure oil does not leak from the front of the engine. Thorough cleaning is critical before the silicone is applied between the oil pan and timing-cover seal contact points. Once a seal is created, the oil pan can be tightened back into place. If the gasket is undamaged, it can be cleaned before spreading a thin layer of silicone between the pan and the block.
Lube the new lifters liberally and drop them back into their bores. Then slide the pushrods through the cylinder-head holes and install the rocker arms. Put the pushrods against the rocker cups. At this point, it's also a good idea to check the pushrod length. Mark one of the valve tips with a black Sharpie before the rocker is installed and spin the engine through several revolutions. Remove the rocker arm and check out the valve tip. If the rub point is in the middle of the valve tip, the pushrod is the correct length. If it occurs closer to the rocker stud, the pushrod is too short--and visa versa if it is too long. Now, you can adjust the valves. Turn the engine over several times via the starter or by hand until the intake lifter of the No. 1 cylinder begins to rise. When it reaches full lift, tighten the exhaust rocker until the lifter plunger just begins to move. From there, tighten the rocker nut 1/2-turn and lock it in place with the jam nut. The idea is to preload the lifter plunger but not bottom it out. Repeat the process across the engine, lashing the opposite rocker (same cylinder) of the one at full lift. When all 16 are complete, fasten the valve covers and install the intake manifold.
The intake-manifold runners must be sealed tight, as a bad seal will suck oil into the combustion chamber, causing sluggish throttle response and poor fuel mileage. Once the new intake gaskets (Fel-Pro or Mr. Gasket) are installed, build up the oil valley rails. Though GM uses cork end seals, we typically spread a liberal bead of silicone across them instead. Set the intake down gently and use the bolts to pull it into place. Following the gasket manufacturer's torque sequence will ensure a proper manifold seal.Now you're ready put the distributor back in the engine. First and foremost, the No. 1 piston must be at TDC. Check this by removing the spark plug and placing a finger over the hole. As compression stroke finishes pushing air out of the hole, the piston is at TDC and properly set. Lower the distributor into the engine while making sure the rotor is pointing directly toward the No. 1 spark plug lead. The trick is getting the rotor to face the proper direction while mating the oil-pump drive with the distributor shaft. If necessary, use a long flat-head screwdriver to rotate the pump drive. A few tries and the distributor should mate with the oil-pump shaft and have the rotor facing close to the No. 1 plug lead. With a little timing advance, the engine should easily fire and allow you to set the total timing. It's also a good idea to change the oil and filter after the camshaft is broken in. As soon as we finished the installation we headed to the Speed-O-Motive engine dyno for some blood and guts fun.
Voodoo Power Testing
Speed-O-Motive is a mail-order parts house as well as expert engine shop offering complete packages that have been tested on its DTS dynamometer. They strapped the engine to the dyno cart and used an internally balanced flywheel. The Hye Tech short-block comes assembled--and balanced free of harmonics when a balancer is added. We used a Professional Products balancer.
A flat-tappet cam relies primarily on oil splash to lubricate its lobes, so it's important to raise engine rpm quickly and vary it between 2,200 and 3,500 rpm, depending on the manufacturer's recommendation. This allows the concave surface of each lifter to develop the minute wear pattern necessary to seat the lifter against its camshaft lobe. After about 20 minutes of break-in, we were ready to cook.
The MSD Pro Billet distributor comes with the heaviest advance springs available to keep low-speed detonation at bay: our engine responded with 32 degrees of total advance at 3,900 rpm. We set the dyno controls between 2,500 and 5,500 rpm. The box-stock carburetor jetting delivered a near perfect air/fuel ratio and the stock camshaft surprised us with 424 lb-ft of torque at 3,700 rpm and 351 hp at 4,800 rpm. Aha, a good cylinder head combined with a properly chosen intake manifold and carburetor will make impressive power. Our stock camshaft sported less than 0.500 inches of lift and 200 degrees of duration at 0.050-inch measured points. The camshaft may have been small, but our blueprinted combo from SA Engine Design came through big time.
After making what we felt was optimum power with a stock cam profile, we began the Voodoo thrash. When the engine fired, it sounded so healthy that several heads turned to it from the engine shop on the other side of the building. It sounded radical. We set timing at 32 degrees. This time we knew the engine would rev high very quickly so we adjusted the testing parameters to monitor information between 2,500 and 6,000 rpm.
The motor pounded out 437 lb-ft of torque at 4,200 rpm and 411 hp at 5,800 rpm, with peak gains of 13 lb-ft and 60 hp. While searching for maximum power we moved the jetting up and down, changed timing curves, and poured 105-octane race gasoline in place of the 91 pump gas. Ultimately, all of the original settings worked best and delivered the stoutest power curve. Surprisingly, the box-stock Holley regulated the incoming air signal so efficiently that the main metering jets were able to deliver awesome air/fuel ratios across a broad range.
For only a few hundred bucks you could have the flat-tappet Voodoo cam kit, or an entire engine for a few thousand. We normally brag about the average power gains our tests provide but here the larger profile of the Voodoo cam allowed the engine to operate across a much wider power curve, which would skew the results to appear far less than they truly were. Instead it's important to look at all the variables, like mid-range power comparisons, as well as peak power differences. In the end, the Voodoo camshaft delivered a potent potion of affordable power. For complete dyno numbers visit www.saenginedesign.com.