This two-paragraph brief from engine builder Jon Kaase was uncovered during our research of the more extensive accompanying article on valve springs, valve clearance, bounce, float and surge.
Excessive valve spring pressure and its effect on lifters
By Alfie Bilk
Excessive valve spring pressure is detrimental to power production, as it creates more friction on the lifters. “On my last year’s Edsel EMC contender,” recalls Kaase,” I had single conical springs and noticed the intake adopting a rhythm and floating the valves about 6,000rpm. So, I installed stronger springs and lost 15hp. I speculated the deficiency may involve the intake valves only, and I put the weak springs back on the exhaust, as those valves are smaller and lighter, and the engine picked up 7hp.”
Most of the power losses implicated by the use of stronger springs are caused by lifter friction. “The stronger the spring,” he explains, “the harder it is to raise the lifter. Even though you get some of it back when it’s closing, you are pushing it sideways against the lifter bore. This sideways force is called the pressure angle. A flat tappet is less threatened than a roller lifter. In the case of the roller lifter, you impose all kinds of pressure on the sides of the lifter bores. So the more spring pressure you apply the more power it consumes. Cup car teams learned these lessons and, as a matter of course, run light valves and light spring pressures.”
To read the about Kaase’s 2017 EMC winning engine click here.