I'll chime in and say that engineers usually apply valve spring rates just stiff enough to close the valves just a little bit beyond the engines intended RPM range. Designing with springs employing a heavier rate, or more preload increases valvetrain stress and requires stronger, sometimes heavier,and more costly followers,tappets,pushrods etc. This also adds reciprocating mass to the valvetrain which results in a slightly less efficient valvetrain. Some of the benefit of the added spring rate will be lost moving the now heavier valvetrain. OK now you've got your engine turning 10% more RPM than the bottom end was designed for. What's gonna fail next. I'll put $10 on the connecting rod, $5 on the bearings.

Whew, sorry about the rant. I've watched many people spend their savings building up half of their engine, only so it's capable of grenade-ing the other stock half leaving 5 quarts of oil on the local 1/4-mile track, and no money in the bank. If you want to hot rod properly, you have to sit down, decide what kind of power you want, and then build your engine accordingly, from one end to the other. That's what the engineers did with the stock engine.


Take it easy JJ, we're only talking about model engines, they're only model engines, they're only model engines, they're only................. LOL