The “lift” of a cam is what determines how far a valve will open inside the cylinder, and how much air and fuel get into that cylinder. Maximum valve lift is calculated by multiplying lobe height at its highest from the base circle of the lobe, times rocker arm ratio. The lift curve can be measured using a degree wheel and dial indicator or more accurately using a computer driven cam profiling system. duration, and my cam has 303/312, it says I should have .679 lift my cam has .675 using 1.6 rockers. … Cam lobe lift, also called Gross Lift, is the distance a cam moves a lifter/tappet. Camshaft Lift and Duration Theory QUESTION: Could someone please explain what the advantage to having short duration like my 270 over say 320 would be? Cam Rpm Range Calculator. They differ only in the way in which the cam's basic profile event positions are specified. Lobe lift refers to the distance that the camshaft can move the pushrod in turn “lifting” the valve off of the seat (opening the valve). A camshaft controls the height and the duration of lift for the valves in the heads of your engine. 10 deg. When you increase the duration of a given camshaft, you shift the power and torque curves upward in the rpm range. dur. The most common rocker arm ratio is 1.6:1, which means the rocker arm gives the valve 1.6 times the lift as at the cam lobe. ALWAYS CHECK SEVERAL TIMES FOR ACCURACY. Lift Another method of improving cam performance is to increase the amount of lobe lift. On a near to stock engine a camshaft around .450-inches of lift, 110 degrees of lobe separation and .218 duration at .050-inch lift should still give you a choppy idle while maintaining strong vacuum at idle. Opening and closing event and duration for most any Valve lift (Plus version only) Asymmetry (Plus version only) Minimum flat tappet diameter (Plus version only) Base circle runout (with Electronics option only) 4-50, 10-50, 20-50 Intensity (difference in durations at .004, .010 and .020 and .050 inch tappet lift, Plus version only) Gross Lift (Valve Lift) Typically camshaft manufacturers list this measurement by multiplying the cam lobe lift by the stock rocker arm ratio, usually 1.5:1. Single-pattern camshafts have the same duration and lift for the intake and exhaust valves, but if there are different lift and duration numbers for the intake and exhaust, these are called split-pattern or dual-pattern camshafts. This calculator is useful for finding out your IVC @ .050" number when your cam is a brand like Comp Cams which typically only provides you with an IVC @ .006" number . It has been around for years, and was written by Dick Jones, used by Mike Jones at Jones Cams, and written into an easy to use and inexpensive camshaft requirement software. The lift curve is a more precise way to look at the cam lift. before/after TDC etc. Engine Calculator (determine engine capacity, compression ratio, deck. Tip: Maximum valve lift can be calculated by multiplying the maximum lobe lift times the rocker ratio. Camshaft Calculator Comp Cams . If the valve doesn't open far enough into the cylinder, there's a restriction in the air/fuel charge resulting in poor engine performance. With a Dial caliper and a calculator, you can figure out Lobe and Valve Lift. The camshaft does not have a larger exhaust, but a smaller inlet profile. 19 new numbers shown in bold face type camshaft application chart notes: comments mech/ dur @ .050” adv. Duration @ .050″ valve lift increases by about 5° when swapping from 1.1 to 1.25 rockers and around 12° @ .200″ The graph below shows lift and duration differences at the valve based on 1.1 and 1.25 rockers (Engle 125) Camshaft Selection Guide . The rocker arm ratio multiplies (increases) the effective lift of the camshaft lobes. Dynamic compression calculator by Kelly Dynamic compression calculator by KB Wallace Racing DCR calculator; RSR DCR calculator; Note: Some dynamic compression ratio calculators (like KBs) ask for an additional 15 degrees of duration be added to the IVC @ 0.050" lift point figure.