There are so many problems with roller cams on the street, its hard to know where to start. I haven't heard of many distributor drive gears being worn out recently. The notch in the lifter that holds the roller is high enough up on both hydraulic-rollers and solid rollers that it intersects the huge main oil gallery that runs through the lifter banks. On a normal roller cam, the lift is high enough to bring the notch into the gallery, resulting in a gigantic oil leak each time a lifter rises. To fix this, cam grinders scale the entire cam down so the lifters don't rise this high. Then, you find that at low rpms like in traffic, roller lifters don't roll all the time- they skid. Skidding wears flat spots on the cam lobes & the rollers. Roller cams are race-car parts and rear racers expect roller cams to be consumable items like wiper blades on a truck.So long-term dependability is suspect unless the revs are kept up, which of course wears the rest of the engine. One also needs stiffer pushrods, shorter than normal ;'cause roller liftera are longer than flat lifters, and much stiffer valve springs to control the heavier lifter. Stock pushrods, springs, retainers and keepers are worthless, and new single-groove valves must be used or you risk having the stock multigroove keepers pop out at higher rpms, dropping a vaalve into the cylinder. Due to the above, I'm not a big fan of roller cams for street cars unless you have much experience with them. And as with nitro or superchargers, the necessary experience "uses up a lot of engines!"