Engine Rebuilding: The Camshaft

Another important camshaft spec is the amount of valve lift. More lift is good, but there are physical limits to take into account such as valve-to-piston clearance and valve spring retainer-to-valve guide clearance and valvespring coil bind issues. A good rule of thumb on modern V8s is .450-.475 inches of maximum valve lift. Consult with the cam manufacturer or physically measure these critical dimensions to be safe, especially if your engine has had special machine work such as decking the block or milling the heads. These measurements have a way of stacking up against you.


Once you have come up with the cam grind that is going to make your engine really sing, installing it is fairly simple. Some tips that make the job go more easily and ensure a successful break-in period are to thoroughly coat the cam bearing surfaces and lobes with a quality assembly lube. Screw a long bolt in the end of the cam to work as a handle to guide the camshaft through the cam bearings. Install a new timing chain and gear set carefully aligning the timing marks on the cam and crankshaft gear. Missing by just one tooth is not acceptable.


Heavily lube the valve lifters with assembly lube and adjust the valve lash before starting the engine. Make sure that the coolant level is sufficient and that you have an external shop fan to blow air through the radiator for break-in. Camshaft break-in is extremely critical to prevent your new camshaft from flattening one or more lobes. Have a timing light hooked up to the engine and the distributor loose before starting the engine so immediately when it starts you can set the timing and take it to a steady 2000 rpm in neutral and hold it there for 15 minutes. At a steady-state 2000 rpm, the valvetrain places the least possible load on the cam to lifter interface. This all may sound difficult—it's not! Just take your time and do it right. The results are worth the effort.

Tips



> Do your homework and select the camshaft that is right for your engine and drivetrain combination.