Rocker Clarification is up!!!

[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

[Billy Nees]

Originally Posted by Lew Silverman

I'll have to check the true lift at each retainer Lew

You don't? Then you're just asking for trouble!

[Stocker 2]

Originally Posted by Lew Silverman

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. Lew

Its easy enough to do. Check all 16 rockers on one valve, figure the true ratio of each rocker, then check the rocker with the largest true ratio on all 16 valves.

[Bill Edgeworth]

Lew,
The discussion is kind of becoming apples and oranges.
The points I was trying to make are;
1 They should not be tossing people without actually measuring the rocker ratio on their motor
2 Tolerance and advertised ratio are two different things and you need to consider both issues because advertised is often not what it works out to be in real life.
And further to what Dennis and X-tech man said I think the reason they relaxed the valve length rule is that it was very difficult for some racers to find a spring that would give the needed seat pressure and rate and fit all the height, diameter and configuration criteria. (Another can of worms to squawk about for those who don’t like our current spring pressure and duration rules or lack of rules that is)
And as Billy mentioned you better be checking every single one for two reasons; to make sure you are legal and not leave anything on the table.
Doesn’t all this talk about checking stuff make you want to run out and buy a 3 or 4 valve or a V10 stocker? LOL

[X-TECH MAN]

Originally Posted by 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

Because most of you guys try to make something out of nothing. Why bother changing rockers in the firt place if your not breaking rocker arms and you still going fast ? The rocker arm is NOT going to give you some out of no where 50 plus HP. The best I have seen or heard of is approx a 3 HP gain on a good DTS dyno and that was from back to back testing of some really screwed up OEM rockers vs a nice set of alum. roller rockers that anyone could afford and buy. Just make sure you lift is correct(not over) and your not trying to use an under cut cam and over ratio rockers or you WILL get cought and DQ'ed..