Sojer

Ok I have my long block set and do to money I don't think I can retro fit me a hydraulic roller (HR) at over 600 bucks. Competition cams also has the same grind for flat tappet (FT) just over 200 bucks.

I know the difference between HR and FT so no need to go into that. I just wonder how much power im leaving on the table. I contacted comp with no answer. The only difference is duration

Hydraulic flat tappet
Range: 2,800-6,800
Intake Duration @ 050 inch Lift: 248
Exhaust Duration @ 050 inch Lift: 253
Intake Valve Lift with Factory Rocker Arm Ratio: 0.584
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.579
Lobe Separation (degrees): 113
Grind Number: 292XFI H13

Hydraulic roller tappet
Range: 2,200-6,200
Duration at 050 inch Lift: 242 int./248 exh.
Valve Lift with Factory Rocker Arm Ratio: 0.584 int./0.579 exh.
Lobe Separation (degrees): 113
Grind Number: 292XFI HR13

Sojer

383 trick flow195

sofakingdom

iTrader: (1)

Generally, the ramps of a flat-tappet cam can't be made as steep as a roller-tappet one.

Think about what happens as the cam is spinning, under the lobe... as it comes off the clearance ramp and the main "action" of the lobe hits the bottom of the lifter, the peak of the lobe can't possibly get there before its flank, and everything still survive. Even before it gets to that point, the lifter has to spin as the cam rolls under it; and it can't go from 0 to light-speed of spin all in an instant. Furthermore, the lifter is only .847" dia; the radius is half that (.4235"); meaning, if the lobe lift is greater than .4235", the peak of the lobe is VIRTUALLY CERTAIN to be somewhere out beyond the edge of the lobe when trying that. Instant destruction when the flank of the lobe tries to rub against the outer dia of the lifter face. That's why racers bore their lifter bores out to .904" and use AMC lifters instead of GM ones.

A roller doesn't have to be concerned about any of that. As long as the valve train can deal with the hammer blow administered from underneath by the cam, all is well.

The "specs" might "look" about the same, but you can be SURE, the lobes are VERY different; and not in favor of the flat version. There will be SUBSTANTIALLY less "area under the curve".