Rocker Clarification is up!!!

[Alan Roehrich]

Originally Posted by Aubrey N Bruneau

We can't control manufacturer's tolerances. I mean REALLY... 1.7 ratio... give or take .05.. ?
Who gives a $%#T ? !
Lift at the retainer below blueprint spec... studs, pushrods, springs, all of the specified configuration and mounting. We haven't changed valves, hacked up the heads, or gone over factory lift at the valve.
WHAT is the problem ? !

Rocker arms, and valvetrain geometry in general, remain as two of the most misunderstood areas of a race engine. About half of what people think they know about the subjects is wrong. Maybe more.

That's not directed at you, personally, Aubrey, but rather a general statement.

[Aubrey N Bruneau]

Originally Posted by Alan Roehrich

That's not directed at you, personally, Aubrey, but rather a general statement.

Yeah ? YEAH ? !
HEE HEE !
maybe I know less than that ?

I'm just sayin... It seems to me that much of the reason NHRA removed the spring pressure and duration rules, was to simplify inspection and enforcement. Of course it changed things. This rocker allowance can be simplified too. Merely have a ratio tolerance... IE; +/- .05, and if lift at valve checks ok... we're good.
I understand that "ingenious" folks may discover advantages one way or another. Positioning of the fulcrum-point for one. Shaft rocker setups are probably more stable, but stud rockers are more user friendly.

I dunno
maybe I'm just simple ?!

[Alan Roehrich]

There already is a rocker ratio tolerance, it is +0.0/-x.x, as they don't seem to penalize anyone for not having enough ratio. You can have the stock blueprint ratio, or less, but not any more than stock. That's tolerance enough, a + 0.0/-x.x is an industry accepted tolerance range.

NHRA checks lift at the retainer, then divides by lift at the cam to get rocker ratio. I'm allowed 0.520" at the retainer, I run 0.518", with 0.306" lobe lift on the cam, for a 1.69:1 rocker ratio.

In Stock, we have to use pushrod length to correct lift, in most cases. That does not change, it's just that with aftermarket roller rockers, you'll need to start from scratch, and get the pushrod that gives you the correct lift, without exceeding the allowed rocker ratio.