stamped steel rocker arm delection
 

just seeing the results you guys are getting on how much lift are you loosing on your stock steel rockers ?? with 220 lbs on the seat ,i see a sizable loss between the difference against measuring with a checking spring and these rockers are not cryoed these a 1.6 ratio rockers gmonde

Re: stamped steel rocker arm delection
 

I've never been able to measure it or verify it. I'd say you'd just about have to do it on a Spin Tron to accurately measure it.

Try checking a roller rocker the same way.

Re: stamped steel rocker arm delection
 

alan,i am sure the a roller rocker will not loose as much if not anything ,i guess i didnt realize how much of the actual lift you mite not be using with the actual valve spring load to get the maximum lift you are required,checking the lift at the retainer with a checking spring vs the actual valve spring is sizable difference gmonde

Re: stamped steel rocker arm delection
 

The deflection I've measured is about .015" from checking spring to race springs on my 396 stocker motor. This is a combination of the pushrod flex, rocker stud flex and the rocker arm itself, not sure how you'd isolate the amount in the rocker alone but it is significant. NHRA checks lift at the retainer, using a solid lifter of the same height, so you can adjust the lobe lift to compensate for the loss from what I understand....

Re: stamped steel rocker arm delection
 

I have .006 extra ground into lob lift to get closer to max lift on the 6cyl engines.

Re: stamped steel rocker arm delection
 

grant:how much spring presure are you running??i know big blocks have a 3/8 push rod but you probably run a 7/16" or 1/2" and the ratio is 1.7 ,,.015 is not bad i am getting more ..020 -.025 and thats with a 3/8 push rod gmonde

Re: stamped steel rocker arm delection
 

Keep in mind, your lift values change as you lose race spring pressure, too.

Wade

Re: stamped steel rocker arm delection
 

[QUOTE=Grant Eldridge;237444]The deflection I've measured is about .015" from checking spring to race springs on my 396 stocker motor. QUOTE]

Grant, sometimes it can be WAY more difference than that. I learned the hard way on this too. Never use checking springs, use the race springs at the pressure your going to run to be accurate.

Wade

Re: stamped steel rocker arm delection
 

gmonde, I run 240 on the seat, 440 open pressure.
wade, I was surprised how much deflection there is in these parts. When I ran the stock size studs you could see them bend turning over the motor! I have since gone to Clark Holroyd's nice stainless thick studs and rockers, but still have deflection.....Clark now welds a re-inforcement onto his rockers above the pushrod seat, like a small bridge across, that might further help....

Re: stamped steel rocker arm delection
 

is welding a brace on the rocker legal in stock??? hhmmmm gmonde

Re: stamped steel rocker arm delection
 

Approved by Glendora.

Re: stamped steel rocker arm delection
 

good to know,,,thanks for the replys ,,good bunch of racers gmonde

Re: stamped steel rocker arm delection
 

If you can get a bigger pushrod in there, and it is legal to open up the holes in the head, you need to go with a 7/16" x 0.125" wall, at the very least you need a premium brand 3/8" x 0.125" wall 4130 heat treated pushrod. You honestly cannot get too stiff a pushrod in a race engine.

Re: stamped steel rocker arm delection
 

Alan, in a stocker engine with a floppy rocker arm, is the extra stiff pushrod that important?

To quote the cliche, "You are only as strong as your weakest link." If you determine the effective stiffness of the rocker arm and then the stiffness of the pushrod, the pushrod is around 20 times more stiff (or stiffer) than the rocker arm. And since these are essentially two springs in series, the lower stiffness drives the total stiffness of the system.

Re: stamped steel rocker arm delection
 

i did go from a 5/16 to a 3/8 chromoly push rod .080 wall,i did do some r&d on the rocker arm with several versions of welded rockers,you can get the rocker to stiffen some but you end up adding so much weight to the valve train it would be counter productive it looks like the bottom of the rocker wants to spread out ,,but if you put a rocker in small tool vise, you can see how it flexes real easy with little turning effort ,,its amazing that how much they flex but the breakage is low gmonde

Re: stamped steel rocker arm delection
 

Pushrod stiffness prevents the pushrod from flexing, and putting its own flex and dynamics into the valvetrain. The rocker cannot even begin to do the damage the pushrod can, the pushrod becomes a spring that flexes and surges, then transfers all of that into the rest of the valvetrain.

Unless you try to make the valve end of the rocker out of lead, you're not going to make the rocker arm heavy enough to make rocker weight into a negative factor.

Re: stamped steel rocker arm delection
 

One of my friends that worked at comp cams told me you can't make the pushrod side too stiff or the valve side too light.

Re: stamped steel rocker arm delection
 

Greg, I agree with this up to a point. 90% of the people we talk to are not talking about stocker level stuff. Their experience is with high lift, high spring rate stuff. Talk to Sacha at Trend. They have some cutting edge stuff right now and use a Spintron as well as some other tools for R&D. My 1.72 intake valve will take a different spring rate and pushrod diameter than a 2.02 cylinder head. It just doesnt automatically cross over....

Wade O

Re: stamped steel rocker arm delection
 

Hey Wade have you put your stuff on a spintron? If so how about sharing some of your results.

Re: stamped steel rocker arm delection
 

Exactly what Wade said, different combo might like different things. And yes it is
possible to (over pushrod) a engine..

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.