Roller Rockers in Stock

[Alan Roehrich]

Kris,
I'm going to try to address as many of your questions in this post as possible, given the constraints of a bulletin board, and the need to not tell everyone everything.

Rocker arm weight is not critical, stock rockers are not heavy, rocker weight in Stock has little to do with valvesprings. It is not the weight of roller rocker arms that will allow higher RPM, an aftermarket roller rocker arm will most often be considerably heavier than the stock part, especially if the stock part is stamped steel, regardless of whether the aftermarket rocker arm is stainless steel or aluminum. For valvesprings and RPM range, rocker arm weight is only important from the center of the stud or shaft toward the valve, what the other half weighs is practically irrelevant.

Again, we have a racer, he can turn X000 RPM, to go higher, he needs more valvespring, and he'll break rocker arms anyway, even without more valvespring. Turning another 1000 RPM will allow him to go faster. Give him roller rocker arms. Now, he can go turn 1000 more RPM, and find out what breaks next. In order to make HP 1000 RPM higher, he needs a new camshaft with more duration or more lobe separation angle or both, since he is lift limited. So, now he's bought new rocker arms, new pushrods to go with them, to keep his lift correct, new valvesprings to turn more RPM, and a new cam to make HP at a higher RPM.

Again, go search and find the principles behind the Crane "quick lift" rockers they sold a few years back. I'll give you a quick hint. The idea behind those rocker arms was you could change the ratio of the rocker arm at low lift, where the valve opens and closes, without changing the ratio at maximum lift (where NHRA measures lift and determines rocker ratio in Stock, by the way) so that you could make significant changes to your camshaft profile at the valve, without altering maximum lift, so you did not have to worry about changing valvesprings, or possibly having to cut the top of the valve guides, etc.

All I'm going to say about valves and valve jobs is that when you change the amount of time, percentage wise, that you spend at certain amounts of valve lift, then you need to change the valve job, and maybe the valve, to take advantage of that change. Remember, we no longer have a real valve job rule in Stock Eliminator, you can run any angle you want, as many angles as you want, the only limit is how far the valve job goes into the bowl of the port and the chamber of the head.

People keep talking about the cost savings this will bring. They ignore the other parts that will get changed. Those parts cost money, too. They ignore the increase in RPM, that will cost money, too. This is not going to make Stock Eliminator one dollar cheaper. This is in fact going to allow people with a lot of money to spend more money with more expensive engine builders who can do more testing to better take advantage of the new rule. This will not bring the "have nots" closer to the "haves", it will only serve to further widen that gap.

So far, we have only addressed the costs inside the engine, with regards to the ability to turn more RPM. That ignores headers and collectors. That ignores torque converters. It ignores transmission ratios. It ignores rear end ratios.

A Stock Eliminator engine is all about the combination and the complete package. A Stock Eliminator car is exactly the same. When you change a rule on one critical part, that rule and that part have effects on the entire car. In Stock Eliminator, it is NEVER about just one part.

[Alan Roehrich]

Originally Posted by 69Cobra

All very good points. You've personally have taken me from wanting roller rockers in stock to not so much. I guess we'll have to wait for the NHRA rule book to know which way to go here.

Kris, to be quite honest, at first glance, roller rocker arms looked like a decent solution to me as well. However, I learned many years ago, at great cost, to look very carefully at rule changes, and be extremely suspicious of rule changes intended to "save racers money". At least 99 times out of 100, rules that supposedly "save racers money", end up costing them a fortune either right then, or not far down the road.

[Dwight Southerland]

Alan, I agree with all your analysis about the deterioration of the spirit of Stock Eliminator, but using the "quick lift" Crane rockers as a point of "evils" associated with roller rockers is not totally a valid argument. The principles of physics that are designed into the Crane rockers can also be incorporated into stamped rocker arms, and the additional low lift increase can be built into the cam lobe profile.

The addition of roller rocker arms into the current mix of contradictory rules in Stock Eliminator is probably of little consequence other than helping a few applications be more reliable.

[Aubrey N Bruneau]

Once again, I'm going to be offering an opinion in an area that I shouldn't... but that's OK... as long as it makes people laugh.
Right now, isn't pretty much anybody running fast, running the absolute most duration in their cam that they can, due of course to piston-to-valve clearance ????? To me, the guidelines on pistons will ALWAYS set the limit there... and as long as NHRA keeps the piston monitored, more duration just isn't in the cards. That, I think, is good. Seperates us from Super Stock.
So.... roller rockers, in one way or another, brining about another 1000 RPM ?... even 500 ?
Can't see it.
Perhaps a couple hundred, but unlikely in the form of a completely altered torque curve.
For me, just providing reliability when buzzing that last 300-400 RPM over the shift point, when passing through the traps.
A LITTLE piece of mind at 120+ MPH !

Alan... as usual, a little over my head ! HEE HEE !
Though, I DO know exactly what you're talking about with the "variable ratio" rocker arm. INGENIOUS, if you ask me !
Money has always seperated the real players from people like me. I'm OK with that.

BTW... Have I ever mentioned that EVERY TIME I read this message board, I learn something ..... ? !

great place !

[FINESPLINE]

Thank you ,Alan, could not have been expressed any clearer in layman terms.------------John

[Alan Roehrich]

Originally Posted by Dwight Southerland

Alan, I agree with all your analysis about the deterioration of the spirit of Stock Eliminator, but using the "quick lift" Crane rockers as a point of "evils" associated with roller rockers is not totally a valid argument. The principles of physics that are designed into the Crane rockers can also be incorporated into stamped rocker arms, and the additional low lift increase can be built into the cam lobe profile.

The addition of roller rocker arms into the current mix of contradictory rules in Stock Eliminator is probably of little consequence other than helping a few applications be more reliable.

Dwight, you're absolutely correct, it is possible to make a stamped rocker arm like the Crane, but it would require someone making a very expensive set of dies to stamp it with, and owning a press. You can make an aluminum rocker like the Crane with any good 4 axis CNC machine, maybe even with a 3 axis.

Yes, you can put that low lift aggressiveness in a cam profile, provided you are not already on the edge of the rocker face.

I disagree, there's a lot you can do when you take the stock rocker arm out of the equation.

[MikeFicacci]

I wonder what the real fast guys that have to deal with rocker issues have to say on the subject. Specifically big block Chevy guys. I know a lot of them check these rockers religiously and do have to deal with breakage from time to time. Curious.

[Alan Roehrich]

Originally Posted by Aubrey N Bruneau

Once again, I'm going to be offering an opinion in an area that I shouldn't... but that's OK... as long as it makes people laugh.
Right now, isn't pretty much anybody running fast, running the absolute most duration in their cam that they can, due of course to piston-to-valve clearance ????? To me, the guidelines on pistons will ALWAYS set the limit there... and as long as NHRA keeps the piston monitored, more duration just isn't in the cards. That, I think, is good. Seperates us from Super Stock.
So.... roller rockers, in one way or another, brining about another 1000 RPM ?... even 500 ?
Can't see it.
Perhaps a couple hundred, but unlikely in the form of a completely altered torque curve.
For me, just providing reliability when buzzing that last 300-400 RPM over the shift point, when passing through the traps.
A LITTLE piece of mind at 120+ MPH !

Alan... as usual, a little over my head ! HEE HEE !
Though, I DO know exactly what you're talking about with the "variable ratio" rocker arm. INGENIOUS, if you ask me !
Money has always seperated the real players from people like me. I'm OK with that.

BTW... Have I ever mentioned that EVERY TIME I read this message board, I learn something ..... ? !

great place !

Actually Aubrey, we (read rectangle port big block Chevy racers) are not running all the duration that will fit in the engine, honestly, I don't think that many people are running every bit of duration that will fit. That's all I will say about that, but we can get more cam in the engine, so can many others.

Again if you accept the premise that you need "x" amount of spring pressure to turn "y" RPM, but you cannot run "x" valve spring with stock rockers, your rockers, for what ever reason, will only take "n" valvespring pressure, then yes, roller rocker arms will lead to a significant increase in RPM.

Also, let's just say that if you could go faster turning more RPM, but you need more valvespring pressure and a better rocker arm, you can change the lobe profile so that the valve opens just a bit slower just before TDC on the intake, and make the lobe faster elsewhere. With a really stout valvespring, you can slam the exhaust valve shut faster, only slowing it down slightly in the last 5-10 degrees before it seats.

[Bill Grubbs]

Using GM rocker arms, we have acually broken 3 rocker arms in 5 years, found probably 8 more cracked. Rocker arms are not a problem for us, but we only run a few races a year.

[Jeff Lee]

Like I said...those that want every .001 to .01 will do what needs to be done. The rest, those that obviously will never find the true potential of their combination, just want reliability.

Case in point...I see a LOT of stick racers that could go .20 to .30 quicker with more refined clutches and if not more refined clutches, then more refined tuning. And I'm not here to bash one brand or another, nor I am I hear bashing one racer over another racers clutch driving / tuning abilities. But you see clutch racers that go "all out" looking for every .01 (I would be in that category) and others that give up two tenths or more because the feel they would rather give up ET performance for what they perceive as reliability and repeatability for rounds. And some just don't believe that ET decrease is possible so they don't even explore. Is this any different than the rocker arm debate? In the end, you will have those that want it all and those that just want to get by and have fun. There's a LOT of Stock racers that are just there to have fun and their idea of fun is not breaking parts and not looking for every .001 with cubic dollars.

And I can't say how many but I know there are many out there running roller rockers with hopes they never get caught. Think about that. Racers are willing to risk a one year suspension for a flagrant rules violation. I believe this guys are after reliability and rounds more than anything else.