* Increasing rocker arm ratio by a point (e.g., 1.5:1 to 1.6:1) increases valve lift by approximately 0.030 inch and adds 2-4 degrees of duration-most cams specs base valve lift on a 1.5:1 rocker.
* Self-aligning rockers shouldn't be used with guideplates.
Springs And Hardware
* Always use springs that are appropriate for your type of cam and are made to handle your intended lift figures and rpm levels. Don't assume the springs you already have will work. Cam manufacturers spell out the spring needed for each application for good reason. "You should never cheap out on valvespings," says Knight.
* Check for valvespring coil bind-there should always be at least 0.060 inch between both the inner and outer coils.
* Likewise, be sure to use the correct retainers and locks with your springs. Check just about any cam catalog, and the proper hardwarewill be specified.
* Check for rocker arm-to-retainer clearance-you should have at least 0.030 inch.
* Once you have the proper valvespring, be sure to set it up properly- the installed height and seat load are listed on the end of the box.
* Remember to check for retainer-to-valveguide-or seal-clearance. The distance between the two should be greater than the valve liftyou're running.
* Use of a spring locator, or cup, is mandatory on aluminum heads, and not a bad idea in any case.
Valves
* Be sure to check piston-to-valve clearance whenever you change a cam or any other valvetrain components. You need a minimum of 0.100 inch on the intake and 0.125 on the exhaust.
Top 5 Camshaft Mistakes From Nolan Jamora, Isky Racing Cams Overcamming An Engine: Mostguys just don't have the experience to choose the best cam and almost always overcam the engine. Then they call and say they have no bottom end or can't get it to idle and that it's the cam's fault. They should have called first.
Wrong Combination: This happens a lot. A guy buys the same heads his buddy has and the manifold he read about in an article and is running the carb his engine came with and has no idea what his stock converter stalls at yet he puts it all together and thinks it will run great. Now you have a guy with a 600-cfm carb, a single-plane manifold, heads designed for 8,500 rpm, a cam that runs 3,000-7,000 rpm, and a 1,800-stall converter. That's just bad news and a waste of time and money. You have to have all your parts working together and all able to work in the same rpm range as the cam.
Wrong LSA: When you get a good combo going and you order the cam, you have to be aware of the right LSA for your cam. Even if you've picked the right cam for your combo and rpm range, the wrong LSA could still cause problems. If you have two cams with the same lift and duration but one has a 106 LSA and the other a 112, the one with a 106 will have better bottom end and midrange and rough idle but less top end, and the other will have better top end and a smoother idle.
Buying A Cam For Your Next
Engine Now: I have guys call all the time for a cam recommendation and tell me what their combo is. Then just after the guy places the order he will say, "So for now I'm gonna put this roller cam in with my Performer manifold and stock heads for a while 'til I can afford the better heads, manifold, and carb. That'll be cool, right? Be smart and buy a cam that works with what you have now, not what you want to have down the road.
 For the ultimate in upper...  For the ultimate in upper valvetrain stiffness, of course, only a shaftmount rocker arm system will do, and these setups are a Jesel specialty. The rocker arms are locked into a single bar running across the head, keeping rocker arm flex-and the resulting losses in duration, lift, and therefore performance-at an absolute minimum. If you're working the track and turning high rpm, shaft mounts should be considered. Jesel's setups start at about $800. |  Pushrods can get overlooked...  Pushrods can get overlooked when putting together a valvetrain, but using good, stiff rods is critical to maintaining valvetrain stability. Stock pushrods don't cut it in any performance application; Crane's threepiece pushrods are a significant step up, and its one-piece, heat-treated chrome-moly pieces are better still. It's also important to always measure for pushrod length using an adjustable tool like the |  Timing chains stretch over...  Timing chains stretch over time, so it's always a good idea to install a new chain and sprocket set like these Crane pieces when swapping in a new cam. The traditional small-block set on the left is a threeposition piece, which allows the cam to be installed straight-up, 4 degrees retarded, or 4 degrees advanced. The billet sprocket LS1/LS6 timing set on the right allows for 5 degrees of adjustment either way by simply loosening the six Allen-head bolts and rotating the cam sprocket. |