ElkySS

iTrader: (6)

i had an older buddy of mine ask me why hyd roller cams usually have more lift than a flat tappet and produce the same hp and rpn range and i didnt really have an answer for him. what are yalls thoughts on this?

fex77k

iTrader: (2)

On the roller lifters only a very small area is contacting the camshaft. On the flat tappet there is more area that is contacted and the ramp rates can be very different from a roller setup.

97FormulaWS-6

iTrader: (1)

HP and RPM range are relative to the entire package. Flat Tappet lifters/camshafts have their limitations though; and to overcome these limitations then a roller style lifter/cam has to be utilized.

The lobes of a flat-tappet camshaft are limited in profile due to the flat surface of the lifter they're contacting and rubbing against. When you change to a roller lifter, the profiles can be a lot more aggressive in profile because the flat-surface interaction is gone.

Also, with a Solid-Roller camshaft, the valve spring pressures can be dramatically higher than a Hydraulic lifter setup. This makes sure the valve doesn't float during high RPMS with aggressive camshaft profiles.

96capricemgr

iTrader: (1)

The whole problem with his opinion is he seems to be blindly flat tappet biased, because that is the only reason I can see for him thinking the HP is the same. That or he is used to flywheel HP numbers and is reading rwhp numbers not realizing the difference.

ElkySS

iTrader: (6)

well the thing he means is, lets take a .500 lift cam. on a hyd roller, that cam is barely more than stock. but for a flat tappet cam, its pretty damn big. my cam is a .582 lift. iv never heard of a hyd flat tappet cam coming close to that

fex77k

iTrader: (2)

You would try to make that up on the rockers, the lobes contact a lot more of the flat tappets so the ramp rates can be pretty steep. Anything is possible with money, but each type has its place.

quik95lt1

iTrader: (7)

well first off they dont make the same power........if they do something is wrong........an roller cam will always make more power than an equilavent flat tappet.......just off of pure parasitic loss.......the roller lifter allows the lifter to litterally do just that "roll" up the ramp versus "push" up the ramp.......allowing for steeper ramp rates (aka more lift with the same or lower duration nubmers).....keep in mind though this added ability down at the cam must have reflecting parts up at the valves......steeper ramp rates = faster valve train velocitys which = the need for better and more accurate valve control..........its not out of the ordinary to see solid roller cams approaching the .700 lift mark or more in some hot street/strip motors.......with aproperly designed valve train with good quality parts and proper geometry it is more than possible to have a somewhat agressive cam that will run for a long period of time

before lash adjustments i have over .700 lift on both sides of my cam at the valve......i street drive it constantly with no issues and my entire valve train has been perfectly operational at 8000+rpm for over three years now.......i checked and tested the entire valve train this year and everything was perfectly fine........i put it right back together........


so as for Flat tappet to roller...........there is no comparison to be made....the only advantage to a flat tappet is the price.....

Wicked94Z

iTrader: (26)

with a flat tappet it depends a lot on the base circle and tappet diameter! You can do more with a chrysler diameter lifter and bbc, 50mm, 55mm, or even 60mm journal than you can with an .750 wheel solid roller valvetrain on your typical sbc. However, I don't know anyone besides those forced by class rules who would ever run a flat tappet instead of a roller valvetrain.