The base circle must be kept large enough to not degrade the strength of the cam, while allowing for enough lift (in conjunction with the rocker arm) to meet all design goals. The cam lobe lift is dictated by the dimension from the base circle of the lobe to the lobe centerline, or peak of the lobe. The basic valve train consists of a cam, or cam lobe, some sort of cam follower, such as a lifter, a push rod, a rocker arm, and the valve (with the associated retainer/keepers, and valve springs).

What are the overall effects of higher ratio rockers? Do they add stress to the engine? Are they safe to use? Do they add power? What precautions should be considered before installing them? The following is a summary addressing these questions. It now appears here courtesy of the author and Eric Douthitt.] [This article originally appeared on Eric Douthitt's, The Pontiac Garage, One thing to consider is that by using higher ratio rocker arms, you are also increasing the effective cam duration,very slightly and increasing the engines ability to breath marginally, but in most cases swapping to a larger cam and retaining the 1.5:1 RATIO ROCKERS HAS MORE POTENTIAL POWER, BUT THE 1.6:1 ratio swap is far easier to do and a good tuning tool.ĪS A GENERAL RULE YOU WILL ALMOST ALWAYS GAIN MORE FROM, A SWAP TO A SIMILAR DURATION ROLLER CAM OR A SLIGHTLY TIGHTER LSA ROLLER CAM WITH ITS MORE AGGRESSIVE RAMPS THAN FROM A ROCKER SWAP ON A FLAT TAPPET CAM In the case of the SBC many times the best gain is found by using 1.6:1 rockers on the intake side only, and retaining 1.5s on the exhaust. You are gaining more of a flow 'curtain' or window, more quickly, as the valve accelerates off the seat slightly faster with the higher ratio rocker. Higher ratio rocker arms may show more of a hp gain. 100 lift, the difference in duration is very minimal, but pragmatically the increase is so small its nearly meaningless in how the engine runs.

Technically YES you add about 1-2 degrees effective duration,because the valve accelerates off its seat faster and the valves open both longer and a bit further off the seat, but look at the charts below, if measured even at. I read somewhere that using 1.6 rr adds to duration is there truth to this?

Cam for goodwrench 350