Roller Rockers in Stock

[Jeff Lee]

Originally Posted by 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.

Cracked is broken. Thats 11 broken rocker arms in five years and you have raced "a few" races a year. If that was two races a year, that would be ten races in five years. That's .9 broken rockers per race.
I remember one year Scott Pearson could only afford to race two national events. He won them both. True he races SS/JA but there are many Stock racers like yourself that can't afford to attend many races. Sure would suck if you broke a rocker in a final round! Even first round breakage would cost you a lot of money.

[Alan Roehrich]

Originally Posted by 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.

A few?

How many Division 2 races did you and Brenda skip this year Bill? We didn't make the tour this year, we'll be back next year.



We have never broken a rocker arm, not in 6 years, although this year was real short. We've broken one 7/16" rocker stud, the poly lock killed the entire engine, including the block. We have only run near 500 passes on one set of rockers, and maybe 300 passes on the other set. No, we ain't as fast as some, but we haven't lost too many heads up races, we've got 2-3 class wins, and we usually go a few rounds fairly often. It may not be a rocket, but it ain't a slug, either.

[FINESPLINE]

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

[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.