GofasterFirebird

iTrader: (3)

I know that when I look at a roller cam for my L98 and I look at a standard flat hyd cam; the roller cam looks as though it has a smaller base circle. Since I am in need of one for the engine in my sig, can I just use a roller cam without having a special "small base" one ground? Or do I need one with an even smaller circle?

ede

not the same thing, you need a cam that says it's "small base circle"

Vader

GFF,

Ed covered it. A camshaft lobe's physical size is limited by the maximum diameter that will fit through the journal bearings when a cam is installed. Most aftermarket cams with increased lifts accomplish that by decreasing the base circle size a bit to allow a greater difference between the lobe peak and base (lift). These changes are usually slight, and are not the same as a "reduced base circle" camshaft, where the base diameter is (by initial design) smaller, to provide more clearance in tight engines (strokers, oversized rods, etc.

By the parts listed in your signature, it does not APPEAR that you would necessarily need a small base circle cam. However, every engine build is different, and depending on the lift you select, crankshaft design stroke, and con rod/rod cap/bolt selection, you may need to install a smaller base circle. Only the builder can calculate and/or measure the space available for a cam lobe, so it's up to you to verify the necessary space.

GofasterFirebird

iTrader: (3)

Ok, thanks. I thought my roller cammed L98 used longer pushrods by .100 inch? Wouldn't this mean the base circle of the cam is smaller? I believe the lifters to be the same height.

ede

factory roller engines use shorter push rods than flat cam engines

five7kid

iTrader: (14)

...because the lifters are longer.