Re: Rocker Clarification is up!!!
 

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 ? !

Re: Rocker Clarification is up!!!
 

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.

Re: Rocker Clarification is up!!!
 

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 ?!

Re: Rocker Clarification is up!!!
 

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.

Re: Rocker Clarification is up!!!
 

How come when I look at NHRA's amendment page this part is crossed out?

Either adjustable pushrods or adjustable OEM rocker arms permitted on any application, but not both.

Does that mean that part of the rule no longer applies?

Re: Rocker Clarification is up!!!
 

They threw me out last year for having 1.65 rockers and the spec said 1.60. The cam passed. Up to yall. I got 1.60's on the car now.

Re: Rocker Clarification is up!!!
 

Jeff, I thought that was just to keep you from getting horsepower!
Jerry

Did they really check or just see what was on the rocker?

Re: Rocker Clarification is up!!!
 

They read the rocker stamp. And when I went to Indy, they read it again.

Re: Rocker Clarification is up!!!
 

Jeff;
In my opinion it was very unjust that you got tossed for what was written on the rocker arm. As Allan mentioned valve train geometry is a very misunderstood thing and just because they say 1.65 on them does not mean they are that ratio on your engine. In many (most) cases when you are running longer than stock length valves you can never achieve the advertised ratio of the rocker unless you run an extremely long pushrod and totally mess up your geometry.
For those that are not familiar with the circumstances that cause this let me explain; many engines like Jeff’s Mopar engines or my Pontiac stuff have converging angles between the valves and rocker studs or pedestals in the case of the Mopar engines. So when you run a longer valve than stock the distance from the pivot point of the rocker to valve tip decreases effectively reducing the rocker ratio. So with longer valves those rockers with 1.65 written on them may not even be 1.6.
I believe the reason the factory designed them this way is to reduce side loading on the studs at maximum lift (maximum valve spring pressure)
So this is just a couple of the issues you have to consider when figuring out your spring/valve/retainer combination.
I’m betting when they tossed Jeff they did not check his rocker ratio they based their decision on what was written on the rocker arm???
Aubrey; If you look at what I have said there is more of an issue with how we use the arms compared to conditions under which their ratio was calculated than a tolerance issue.

Re: Rocker Clarification is up!!!
 

Bill I think you can use longer than stock valves in super stock, but not in stock.