School me.....please.

 

because the peak on a flat tappet cam is too sharp. it would beat the roller to death.

 

The heal of flat tappet cams have a slight taper on them to "spin" the lifter to prevent wear. Roller lifters require a flat lobe.

The contact characteristics of the two types of followers require completely different lobe shapes to produce the desired valve motion. It's all in the kinematics.

 

Ok. That makes sense. Always wondered why.

 

i thought that a roller lifter was allowed steeper lift patterns than the flat tappets.

 

They can, but the whole way the lifter interacts with the lobe is different. The afore mentioned part about flat tappet lobes having a taper to spin the lifter, but also that a lobe is interfacing with a round surface instead of a flat one makes the shape of the lobe needed completely different to get the valve accelerating and decelerating at the right rates at different points in the lift curve.

 

The advantage of roller cams is more aggressive ramp rates and the valve is held open farther, longer. Beyond the fact that it just wont work, it's kind of pointless to bother. Youd just get the same flat tappet grind with a bunch of extra valvetrain weight.

 

Not really. As mentioned, the lifter interaction with the lobe is completely different, so a roller lifter on a flat tappet lobe (ignoring the taper issue) would be an absolute dog. Early lift would be practically non-existent.

 

 

just to make it clear, the polished looking one is for rollers the dull one is flat tappet