"Bolt-In" Cams: "Bolt-In" means that the cam manufacturer believes the cams will go into your motor with the rest of the parts all stock, and generally without any clearancing work as well.In other words, they install just like a set of the original cams.So in a nutshell, more overlap turns over more control of your engine's powerband to the pipe. If you've got a pipe with the sound or looks that you like, but it doesn't work well at the rpm you like to ride, choose cams with less overlap.When using cams with a lot of overlap, your torque curve will essentially be a map of how the pipe behaves at different rpm's. TDC lift figures are also very important, and closely related to overlap. Contrary to popular misconception, valve to piston clearance has nothing to do with maximum lift, because maximum lift always occurs with the piston well down the bore.Download a copy of our Static and Corrected Compression Ratio Calculator to help decide how much compression you need with a specific set of cams. Overlap is the sum of two of the timing numbers, exhaust close and intake open. Overlap is the number of crankshaft degrees in which both valves are open at the same time. It happens as the exhaust cycle is finishing and the intake cycle is beginning, with the piston passing through top dead center.
To retrofit 2000-up cams to 1991-1999 motors, update the pinion gear (available below).
Proper cam selection is critical to the performance of your XL engine.
At HAMMER PERFORMANCE we have many years experience building XL engines and we've used literally every XL cam available at one time or another.
Street grinds typically close the intake valve anywhere from 35 to 55 degrees after bottom dead center (ABDC) Race grinds tend to close it anywhere from 55 to 70 degrees ABDC.
One other note on intake close timing: the later you close it, the higher compression ratio you need, since no compression takes place until the valve is closed.
High TDC lift figures can also cause issues with valve to valve clearance, but if we set up your heads and you told us what cams you're using, we've checked it and set it for you.