Re: stamped steel rocker arm delection
 

Glenn, I would love to have the $2500 to rent a Spintron for a day. My pockets arent near deep enough for that. But, my guy who does use one daily has filled me in on all of the details for my specific engine. Valve, retainer and lock weight, cam profile, pushrod length, diameter and wall thickness among a couple of other things. I think he has a pretty good handle on whats happening with my combo. What specifically did you want to know? I could be persueded to release a small amount of info, lol.

Is this the Glenn from B&B Automotive in New York?

Wade O

Re: stamped steel rocker arm delection
 

Everything you say is correct, but why do you feel the rocker can not become a spring that flexes and surges, then transfers all of that into the rest of the valvetrain?

When I was an engineer for Eaton, the very first thing we did in analysis of a valvetrain is to determine the effective mass at the valve and the valvetrain stiffness. You then determined what the limiting factor speed wise was for the valvetrain.

Either it would be lack of valvespring force or a harmonic issue in the valve train. The harmonic issue was then divided into a mass or stiffness issue.

By far, the most effective way to increase speed is the limit mass of the valvetrain on the valve side.

On a standard pushrod valvetrain, the best place to increase stiffness is at the rockerarm. Per David Vizard's SBC valvetrain book, a SBC rocker has a stiffness of roughly 5,000 lbs/in. I've lost my previous calcs on pushrod stiffness, but I think it's roughly 50,000 lbs/in.

Re: stamped steel rocker arm delection
 

Chris, you have to find 'balance' between push rod stiffness and the valve spring controlling your valve. When you have balance, you will eliminate 99.9% of your rocker arm failures. The event that causes rocker arm destruction is the 15 to twenty thousandths valve bounce off the seat. Each valvetrain will be somewhat different due to the weight of the valve(s). BTW, the weight of a push rod has to exceed 1.25 POUNDS before it shows a negative effect on the spintron(from a great NASCAR engine builder).

Tell your folks Hi, from Lynn and I and I hope you are all well.

Re: stamped steel rocker arm delection
 

Chris, I never said the rocker was not a problem. It is, but there's not a lot you're going to do about it. All we can do in Stock is to work on what they let us.

The calmer you make the pushrod, the less harmonics it transfers to the rest of the valvetrain, especially the rocker. The stiffer you make the pushrod, the less it acts like a spring. The less the pushrod acts like a spring, the less of a beating the rest of the valvetrain takes. If you can stop or reduce the spring effects the pushrod drives into the rocker, you can calm the rocker as well.

Re: stamped steel rocker arm delection
 

To add to what Arnold said: I have found valves that are actually acting like a springboard when they hit the seat. ( close inspection of the valve and valve seats will show it) When the problems start there it is almost impossible to stop. Valve material and design is usually the problem when a valve acts like a springboard.

Re: stamped steel rocker arm delection
 

Which flexes less, late model rail type rockers or the old style sb rocker? I know a stiffer pushrod helps and guide plates help control also, but you can't use guideplates with rail rockers i believe.

Re: stamped steel rocker arm delection
 

Mark, just to hazard a guess, I'd say the premium aftermarket stamped rockers for 7/16" studs are probably the stiffest, due to materials. I really don't much care for the rail rockers, I prefer the guide plates and 3/8" pushrods myself.