Wrong Type Of Cam:
The choice between hydraulic, solid flat-tappet, hydraulic roller, and solid roller is very important. If your engine comes hydraulic and you only want a little increase in performance, stay hydraulic. If you want to pick up a few thousand rpm and not have to check lash, run a hydraulic roller. If you want the sound and rough idle for a street/strip combo and don't mind adjusting the lash, run a solid flat-tappet. If you are racing, it's almost always best to go full solid roller. Get with a cam tech and go over the setup to pick the right type of cam with the right specs.
Billy Godbold,Comp CamsCHP: How heavily is Comp involved in racing?
Billy Godbold: Right now, it's close to half of what we do and it's extraordinarily diverse.
CHP: Does what you learn on the track find its way to the street?
BG: There's tremendous trickle-down.It's wild. We've only got one team, and each person has a specialty. Race, OE, street...it's all the same team working on it.
CHP: Can you give us a specific example?
BG: The valve timing events of our Thumpr camshafts are almost identical to road-racing apps, especially 24-hour endurance racing.
CHP: Really? I thought the Thumprwas particularly designed for a"rumpity" sound.
BG: The reason we use that strategy is that drivers get tired and don't want to shift, so this cam lets the car pull if it's a gear high in a turn or a gear low on a straight. You get an early torque peak and a long, gentle fall-off. It's more fun to drive.
CHP: Tell us a bit about designing camshafts.
BG: Mine is the first generation that did cams with a Spintron. Before, we did it by the seat of our pants, on the dyno, and tried to imagine what's going on. With a Spintron, we can see where issues are. It lets us know exactly where we're getting in trouble.
CHP: Any parting words of wisdom?
BG: There's nothing wrong with not being able to afford everything at once. You just need to have a plan, the what, where, and how, to create an awesome street combo.
James Humphrey, Lunati
CHP: What was the genesis of the Voodoo line?
James Humphrey:Lunati has made excellent cams, but in today's marketplace, if you stay with the same thing, you don't last.
CHP: So what's different about the Voodoo cams?
JH: The lobe acceleration rate, the increased area under the curve, and our unique approach to duration at 0.050. We've also paid attention to lobe separation. Wider separation makes for a wider powerband. The Voodoo cams have a 110- and 112-degree LSA, which means they'll work with aftermarket four-barrels and OEM computers.
CHP: What did you mean about your approach to duration at 0.050 inch lift?
JH: With the advent of improved heads and valve springs, we can get away with a lot more than we used to. That means bigger, better profiles. You get more air throughout the range with a quality head.
CHP: Have you introduced any other new pieces?
JH: We've added beehive springs and a line of pacalloy springs, which are extremely high quality yet affordable. We've also added retainers and locks as well as new solid lifters.
CHP: What trends are you seeing in what the public wants?
JH: I still see a lot of hydraulic flattappet action, but the trend is leaning more and more toward hydraulic rollers. You don't have to rely on maintenance or rotation but can still get fairly aggressive.
Speaking of advancing or retarding... As we've noted earlier, a cam's intake/exhaust centerline is the theoretical maximum lift point on the lobe, expressed in degrees after TDC. This centerline is used to tie the valve timing to the crankshaft rotation. Almost all our cam experts agree that cams tend to run best with a bit of advance in place, so the 'sticks come ground to deliver this advance when installed in the straight-up position. A multiple-position timing set allows you to move the intake centerline forward or back. What happens if you advance or retard the cam? With the former, the rpm range is moved down; with the latter, it's shifted upward. Knight recommends always starting out at the straight-up position. "You can refine from there," he says, "but if you're seeing a benefit from moving more than 8 degrees advanced or any degrees of retard from 0, you don't have the right cam."
Proper-length pushrods are also the key to creating correct valvetrain geometry. In short, with the right pushrod in place, the rocker-arm tip rolls from the intake side of the valve tip, across its center as the cam reaches midlift, to the exhaust side of the tip at full lift, then back to the intake side. It's a relatively simple measurement to take and implement, but it pays off in valvetrain longevity and improved perrformance.
Cam cards come in a variety of configurations, but they all serve the same purpose, which is to tell you just about everything you should know when it comes to your cam: its lobe separation angle, intake centerline, each of the valve opening and closing events, valve lift, advertised duration, and duration at 0.050 inch. This Comp card refers to a hydraulic flattappet cam, so the valve adjustment spec shows zero; with a solid or solid roller cam, the lash setting would be shown. This card also reminds the installer that new valvespringswill be needed for this 'stick to work properly; a quick call to Comp with some cylinder heads specifics will yield a recommendation.