quote:DeTom, you said you are not going with roller tappets to keep weight down...I didn't think about that. What's worse the friction from a flat tapped or the extra weight of a roller lifter with less friction? My cam lift will be similar to DeToms at .580 ballpark. I'm using behive springs with steel retainers.
http://www.coasthigh.com/product-p/scp1024.htm
As long as you have good lubrication the friction for both is about the same because it is the oil film that it slides across. They use rollers to allow more agresive valve opening, in that they can make the ramps on the cam itself steeper if a roller is used because a flat tappet would bind on too step of a surface. Even at the same lift a roller tappet CAM will force open the valve farther, faster in the opening phase but will require more force to do so. It can also hold the valve open at full lift longer because it has a steeper ramp there too, but here again, you have to have more spring force to get the valve to accelerate faster. There is an advantage in volumetric efficiency, but it also beats up the valvetrain quicker because higher force loadings are involved. I like the idea of slightly increased power without sacrificeing longterm longevity. But then again, I am happy with 375-350 horsepower. Most folks no a days demand a thousand. I am not all that greedy myself.
