Rocker Clarification is up!!!

[Jeremy]

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?

[Jeff Teuton]

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

[Bill Edgeworth]

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.

[Larry Hill]

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

[denbreeden]

Any aftermarket steel valve permitted, must retain stock head and stem diameter is what the rulebook says, nothing about length.


Dennis Breeden
A/SA

[X-TECH MAN]

Longer than stock aftermarket stainless steel valves ARE LEGAL in stock in both NHRA and IHRA and have been for many years.

[Lew Silverman]

OK! So everyone is right! The rules are clear as mud, but shouldn't be that hard to understand.

Manufacturers tolerances are suspect, so everyone needs to have a little cushion so you don't go over the spec. I don't have the capability of checking the "true" ratio of each of my rocker arms, but if each one is different, I'll have to check the true lift at each retainer, and hope I get 16 measurements that are the same. It's quite possible that will take more than 16 rocker arms to accomplish. Maybe I'll just be happy if they're all below the maximum lift.

I'm really not trying to be obtuse here, just trying to understand why the rules have to be written so vaguely that they invite all of this discussion! Most every other aftermarket part is identified by number in the Guide, for a reason.

Lew