Rocker Clarification is up!!!
 

Go to nhra competition rules ammendments!!!!

Re: Rocker Clarification is up!!!
 

I would say that clears up a lot of questions!

Re: Rocker Clarification is up!!!
 

do the roller rockers have to be steel or is aluminum ok?

Re: Rocker Clarification is up!!!
 

I think they still need to add one line -

Aftermarket rocker arms must have same ratio as OEM for engine horsepower claimed

or

OEM or Aftermarket rocker arms with any ratio permitted

I do like the new rule about being able to reinforce an OEM steel rocker arm!

Lew

Re: Rocker Clarification is up!!!
 

Anybody have a brand name and part number? It would be nice to see what we need to buy.

Re: Rocker Clarification is up!!!
 

Re: Rocker Clarification is up!!!
 

Those, if they're going to be listed, would be in the "Accepted Products" list.

As of just now, there is no rocker arm category listed.

Re: Rocker Clarification is up!!!
 

So if I show up with Harlan Sharp 1.7 roller rockers on my 327 I'm OK? Are they going to check the ratio?

Still a lot of "what if's"!

Lew

Re: Rocker Clarification is up!!!
 

Rocker Ratio is defined in your Engine Specifications in the guide.

Re: Rocker Clarification is up!!!
 

I spoke to Nhra tech last friday and was told stock ratio, dont know why its not
on the new ammendment. As pointed out earlier it is in the engine blueprints and
probably why nothing has changed ratio wise. I was also told there will not be a accepted
or required list, Any commercially available unit that fits the outlined requirements
will be just fine.

Re: Rocker Clarification is up!!!
 

Thanks, Ron! That makes sense, I guess, although I still wonder why something wasn't said about the rocker arm ratio in the amended rules.


Lew

Re: Rocker Clarification is up!!!
 

This is still confusing, as the 2012 rulebook still states that guide plates can be installed, and the new rocker rule goes against that statement? Any thoughts Travis?

CAMSHAFT/LIFTERS

Camshaft must retain stock lift for horsepower claimed per NHRA
Technical Bulletins. Front-wheel-drive vehicles and stock trucks,
maximum lift is limited to .430-inch or OEM, whichever is greater.
Aftermarket OEM-type replacement lifters permitted. Lift checked at
valve retainer, with zero lash. Hydraulic lifter cam will be checked
with pushrod and rocker as run, plus solid lifter, at zero lash.
Plunger height of checking lifter will match extended height (no
preload) of hydraulic lifter. Hydraulic lifter may not be plugged or
bottomed. Aftermarket gear drives/belts prohibited. Aftermarket
timing covers permitted as long as OEM-type timing gears are
used. Adjustable pushrods or adjustable OEM rocker arms (not
both) permitted; must be same or greater weight as stock. Pushrod
guide plates permitted. Cylinder head may be clearanced for larger diameter

pushrods.

Sean

Re: Rocker Clarification is up!!!
 

Sean, all i see is about Stud Girdles being Prohibited.

Re: Rocker Clarification is up!!!
 

I 'd call Southland Speed since they advertise on here and I don't see JEG'S on the site.....lol. But thats just me :)

Re: Rocker Clarification is up!!!
 

Yeah, not the smartest rule they could make.


Scott Helms, check your PM's bro.

Re: Rocker Clarification is up!!!
 

Some time back on another thread under the Tech section, we discussed push rod length and how to optimize it. Quite a lot of discussion resulted in the description of the desmodronic valvetrain commonly found in the various Kettering overhead valve engines. What it boiled down to in layman's language was that push rod length could affect rocker arm ratio.My 327 has a max allowable lift on the intakes of.390". That means that lobe length at the cam has to be .260" with a perfect 1.5 ratio rocker arm. We all know in the real world that nothing is ever perfect in consistant enough quantities to ever be counted on.The trick here is to have a valvetrain where the lobe lift is 2/3rds the valve lift. We discussed how a short pushrod with the same cam lift,rocker arm and lifter could result in a different lift at the valve than a long pushrod. The means for determining rocker arm ratios is to first determine valve lift at the retainer, as it's checked by NHRA,then divide that figure by the cam lobe lift, checked at the lifter,and it should verify the ACTUAL rocker arm ratio. With a roller tip rocker arm,some of the problems associated with OEM stamped arms vanish, but it will be interesting to see what new factors creep up as we start doing this.I am about to reassemble my 327 stocker motor soon, I'll compare results obtained with it as it goes together. I bought a new Dart block,had Gregg Luneack machine it and deck it, I'll soon see what possibly changed. The discussion we had on the Tech section a few months ago got so involved that before we were done, the various compilations of info resulted in a mini-textbook on push rod length. Fun reading!!

Re: Rocker Clarification is up!!!
 

Greg
I am playing with a couple of stocker motors at present and I am working with the cam grinder. In doing so I asked the cam grinder what ratio rocker did he develop the cam lobe around. He told me that in this case it was slightly less than the factory designed ratio because most will never be long. Almost all will be short on ratio. So I sat the rocker arm up upside down in the mill an used a laser beam to find my pivot point so that I could establish my pushrod "designed'" length. I then installed the cam between centers and plotted the area under curve. I then put the head on and lifter in with that rocker arm and using that laser determined pivot point, I adjusted a pushrod for my optimum lift. I then went thru the motion of determining area under the curve again and it followed area under the curve as a cam. Now I will move push rod lengths around a see area under the curve again and let you know what I find. But with the new rocker arm rule and the ability to make all rockers exactly the same correct ratio, I think we will see people adjusting pushrod more than ever just to get their lifts in spec and they may loose area under the curve as a result. My .02 worth
reed

Re: Rocker Clarification is up!!!
 

So in the example that Greg gave with his 327, a camshaft with a lobe lift of .260 and a rocker arm ratio of 1.5 would give a theoretical lift at the spring retainer of .390, as specified. Could you not also use a camshaft with a lobe lift of .24375 and a rocker arm with a ratio of 1.6 to get the same lift at the retainer and still make spec? It would also, I think, open the valve faster and improve cylinder filling. Another reason to fabricate a head dyno!

Lew

Re: Rocker Clarification is up!!!
 

Unless the rule has changed, a 1.6:1 rocker arm on an engine that came with a 1.5:1 rocker arm is illegal in Stock Eliminator.

Re: Rocker Clarification is up!!!
 

Don't see why ratio would matter as long as valve lift spec wasn't exceeded...Again, the spring pressure deal "opened" up this can of worms...

Would think though...that MOST stocker cam lobe profiles were created with the STOCK rocker arm ratio in mind....notice that I said MOST...but not ALL...

Re: Rocker Clarification is up!!!
 

what about vice-versa?

Re: Rocker Clarification is up!!!
 

Correct-A-Mondo............Alan is 1000% correct......brush up on your stocker racing history. Remember the Crane stamped steel rocker that came in 1.6 for the small block chevys. Several big name stocker racers were DQ'ed many years ago by NHRA for using these even though the lift checked correct at the retainer. It changes the rate of lift and produces more flow as the valve rises off the seat. Its DUMB to even think you could use rocker ratios greater than what the engine spec. book calls for. Stop trying to reinvent the wheel.

Re: Rocker Clarification is up!!!
 

Less would gain you nothing unless you had some major piston to valve clearence or geometry problems with some odd ball engine. The OEM stock steel stamped rockers are way less to begin with.

Re: Rocker Clarification is up!!!
 

If the stock stamped rockers were less and all the cam makers know this. What are the odds that just switching to a aftermarket roller rocker will bump the lift at the retainer over the allowed limit?

Re: Rocker Clarification is up!!!
 

exactly my issue....
and while we're at it, is it legal to run less lift than spec?

Re: Rocker Clarification is up!!!
 

Yes.....some do to gain piston to valve clearence and use more duration. Duration and overlap is more important than valve lift. Maybe not so much with the bogus aftermarket pistons of today which give you more piston to valve clearence than the OEM unit.

Re: Rocker Clarification is up!!!
 

[QUOTE=X-TECH MAN;305163 Remember the Crane stamped steel rocker that came in 1.6 for the small block chevys. Several big name stocker racers were DQ'ed many years ago by NHRA for using these even though the lift checked correct at the retainer.[/QUOTE]

How does NHRA check rocker ratio at teardown?

Re: Rocker Clarification is up!!!
 

I don't know how NHRA does it but I would think the easiest and most accurate way would be cam lift divided by valve lift.

Re: Rocker Clarification is up!!!
 

That's right! Anyone making the switch to roller rockers will need a new cam ground. Sounds like the cam manufacturers were all for allowing aftermarker roller rockers.

Re: Rocker Clarification is up!!!
 

It's called "area under the curve". Making the rocker move the valve faster than the lobe can with the stock rocker ratio gives you more area under the lift curve.

Re: Rocker Clarification is up!!!
 

Thats for the racer to check to make sure this dosent happen. Not the cam company or rocker makers.

Re: Rocker Clarification is up!!!
 

Thats backwards.......divide the lobe lift into the valve lift. The number you get is the R.R. Ifs its over then your DQ'ed. There is a couple of ways to get it.

Re: Rocker Clarification is up!!!
 

Seems that the last several posts have verified what I wrote in my post on page 2. We need to look at some absolutes- two sources of absolutes come to mind- those provided by the engine designers, and those mandated by the sanctioning body.
Absolute #1-- Valve lift must be OEM or as specified.
Absolute #2-Rocker arm ratio must not exceed OEM.
Cam lobe lift isn't too well specified. In order for #1 above to be achieved in a desireable fashion,#2 has to be followed as well. In the case of a small block Chevrolet,ideal results are when valve lift is half again lobe lift.In the event lobe lift is correct,and valve lift is lacking, then another means has to be employed to achieve it. That is where push rod length comes into play. Now, you don't really want exact specs here, you want to be safe by .005-.010". This is because the tech guy at teardown might not read mikes the same way I do. Also, expansion due to heat might cause results to vary. If my intake lift spec is.390". I would love to see an actual.379-.382".Now, if I achieve this spec with a very long pushrod, I'm getting the maximum extra duration and rate of lift out of that valve train.
Now, the other booby trap has to be recognized. If you checked lobe lift, it passed right on the number, used a very close to optimum, a long push rod, you could still result in a rocker ratio that is a bit over, however,that couldn't help but make the valve lift over as well.Optimally, a cam lobe with the correct lift, a valve with lift good by .008-.010, and a rocker arm ratio of 1.47-1.49 would be the best of all worlds. Now, good luck getting it!

Re: Rocker Clarification is up!!!
 

I am well aware that it is the racers job to check I was just curios what the odds are that it is going to come up with a little extra lift. With the old set up knowing the ratio was generally a little short I assume that the cam company's add a little lift to compensate at the request of the racer. Not blaming them for any thing,
I was just wanting to know what the odds are you are going to have to change cams when switching to roller rockers that have a true 1.5 ratio.

Re: Rocker Clarification is up!!!
 

Probably a 50/50 chance or better. Id be talking to the cam grinder and find out what was done.

Re: Rocker Clarification is up!!!
 

Any good machinist reads the "Mikes" the same way. I dont know about other tech guys but I used a dial indicator when I checked lift (and duration/overlap) in the old days. The Govt. spec. on tolerance of either a mike or a dial indicator is plus or minus .001(one thou.) My personal tools were alway certified by myself. ....I worked almost 18 years in a Navy Calibration lab after working as a tool maker for the Navy. Its not rocket science.

Re: Rocker Clarification is up!!!
 

We've just been through this upgrade with rockers, pushrod length etc. What we saw was changes in lift at the valve due to the rocker change, but also as we varied the pushrod length and went from break in to full racing valve spring pressure. After sorting out the rest, we had to order a cam with .006" less lobe lift to get back under our allowed lift of .398" on the 325hp 396. You get rid of a lot of deflection going to the new rockers, so if you'd used a cam ground with extra lift originally to get close to the spec, it would be important to check it after installing the roller rockers. Just my 2 cents.......

Re: Rocker Clarification is up!!!
 

You obviously were trained well and made constant use of your level of skill. Some people weren't and didn't.I don't know about some of these people masquerading as machinists out therehowever. How many times did you get parts back out here that weren't done the way you wanted them done?

Re: Rocker Clarification is up!!!
 

LOL......More times than I can count. When I went to metal parts inspection a LOT of parts for air craft ejection seats and stuff that goes "BOOM" came in from vendors out of spec.

Re: Rocker Clarification is up!!!
 

BINGO ! A smart racer right there. Less deflection but more so in more accurate Rocker Ratio. But check what you order. Not all rocker arms are made equal. Some out there are as bad as OEM or worse. Some of the best are the ones you stocker guys are not allowed to use.