Roller lifters reliability

[Bowtie]

a roller will give you MUCH better rise at any RPM. Rise on a flat tappet is limited because with too much rise on a flat lifter, the leading edge of the lifter will dig into the cam lobe. Roller cam lobes can look almost square in profile while flat tappet cams have to have a gradual 'ramp' to let the lifter stay in full contact with the lobe. The trade-off is the fact that a roller has to stay in line with the lobe, whereas a flat tappet cam/lifter set is ground off-set a couple degrees to spin the lifter while moving up and down, thus evening out wear on both components. i say again...unless you are a serious racer, your best bet is to dump money into good heads (and good headwork at your local speed shop)...and let em clean up your intake manifold ports too.(another item to note on a roller..you need a higher spring tension on a more aggresive cam profile to make sure the lifter stays in contact with the cam and doesn't 'float'. that higher spring tension coupled with the uni-directional wear can grind a cam round very quickly some times. prime the oil pump with an oil pump drive shaft stuck in a drill prior to break-in and use the proper assembly lube..) a flat tappet motor will last much longer than any roller will. no exceptions.( keep in mind...i am a HUGE fan of roller cams...lots of bang for the buck... it just doesn't make a good 20k-mile-a-season cruiser.) i plan to put 100k miles on my cobra...my dyno sheet says i made 507 HP on pump gas with 9.8:1 compression (max torque was 503) with solid flat tappets and only 406 cubic inches. HALF of the cost of my motor went into the heads (the flow numbers on my ProAction heads were outstanding...e-mail me if you want the numbers). So what have we learned today? Roller.... big gains in HP at the expense of longevity. Flat tappet... you won't get as much power, but you can get close if you spend a few bucks on good heads and headwork, and your motor will last much longer.