Is this BS?
I read an article in Sept issue of Muscle Car Enthusiast and they talk about how far off the stock rocker arms ratios are. So I've typed out most of the acticle.

For example, a small block Chevy calls for a rocker ratio of 1.5:1. This means that the rocker arm will multiply the camshaft lobe lift by 1.5 times. Pretend the lobe lift cam is .300-inch on both intake and exhaust lobes. When multiplied by the rocker ratio of 1.5, the gross valve lift works out to .450. No big deal, right?

Wrong! In many cases, a stock stamped steel rocker ratio will only check out to 1.43:1 or less. As a result, the gross valve lift works out to .429-inch. As you can see, the cam LOST about 5% of it's effective lift. And it only gets worse as the lobe lift numbers increase (cam more radical).

Reason:
Volume. The Bow Tie bunch has produced in excess of billions of rockers produced. The dies wear out and hundreds of thousands of rockers make it out the door.

Answer:
To maintain the stock height valve covers the options diminish quickly. The 1st option is to check a bunch of rockers until you find the highest effective ratio and are close to one another. If you have hydraulics then you'll have to replace one with a solid lifter on one camshaft lobe. Slowly and carefully tighten the rocker arm to zero lash. Next, install a dial indicator to read off of the valve stem side of the rocker arm. Manually turn the engine through 1 complete revolution. Compare this gross (zero lash) figure to your cams specs. You may find numbers that don't correspond.

To verify the figures, either cross reference the number with your cam card or check the lift at the lifter and multiply that number by the engine rocker ratio. This number is the theoretical gross valve lift. Most SB rockers check at between 1.4:1 and 1.47:1. Few attain the advertised 1.5:1 ratio.

You can rummage through boxes of new rockers until a perfect set is found or install a set of aftermarket rockers. Another option is to examine the line of stamped steel rockers offered by Crane. They are beefier in the pushrod cup location and don’t have a build up of metal flash in the area of the pushrod oil hole. The slot is slightly larger than stock. In addition the valve-tip contact surface on the Crane rocker is smoother than the stock piece. In the case of Chevs, grooved rocker balls are standard equipment and so are the jam nuts. The ratios are on target (Crane).

Competition Cams makes a Magnum rocker that’s a cross between roller and stock rocker. They feature a true roller tip coupled with a conventional grooved rocker ball/jam nut fulcrum arrangement.

What’s the benefit of the roller tip? With the conventional stamped steel rocker, the tip (or area which contacts the top of the valve) sweeps or glides across the tip of the valve as the cam forces the rocker nose down. The sweeping action becomes rollerized instead of dragging a steel rocker across the valve tip, the rocker rolls over the valve tip. With a roller tip, valve guide wear is reduced and so is the actual wear on the face of the valve tip producing more HP gains.

How much you say?

Dyno tests with a 454

TORQUE:
RPM / STOCK ROCKER / MAGNUM ROCKER / DIFFERENCE
2000 / 445 / 445 / 0
2500 / 454 / 456 / +2
3000 / 452 / 455 / +3
3500 / 431 / 440 / +9
4000 / 394 / 407 / +13
4500 / 352 / 368 / +16
5000 / 299 / 312 /+13

HORSEPOWER:
2000 / 170 / 169 / -1
2500 / 216 / 217 / +1
3000 / 258 / 260 / +2
3500 / 287 / 293 / +6
4000 / 300 / 310 / +10
4500 / 301 / 315 / +14
5000 / 285 / 297 / +12

So has anyone swapped out their stock OEM rocker arms on their small blocks or big Blocks? Or has anyone gone to roller rockers with the stock lifters?

I have heard the stories of NHRA stock eliminator guys going thru 100's of factory rocker arms to get 16 good ones.
I have also seen people change pushrod lengths to get the most lift out of a rocker arm instead of the best wipe pattern accross the valve stem tip.

One mistake people make is using old stamped steel rocker arms with a new performance cam. The old rocker might have been used with a cam having .400 valve lift, and you put it in an engine with .450". The wear pattern between the
rocker and ball is worn for the low lift cam, and now the new cam pushes the rocker arm further and the ball hits the unworn area. Sometimes the rockers can break, and someone will say " oh you should have put long slot rockers on it"

Elgin industries has a nice stamped steel rocker arm I have used with great results. I like the Cranes too.

How about roller rockers without roller lifters? Any gains or a waste of time?

I will not dispute the reliability,improvement of ratios and less friction using roller rockers.

I will dispute that swapping from stamped rockers to rollers will NOT net you any ET or MPH gain.
Nothing to be gained timeslip wise

I'm actually in the same boat now, I've swapped cams twice, have some nice trick flow heads, basically the whole top end has been replaced EXCEPT the rockers, still running hte stamped steal.

I dont have a big budget so is there a better rocker out there than http://store.summitracing.com/default.asp?target=partdetail.asp&part=SUM-141507 for around the same price?

Also going from stamped to roller means I need to install the guideplates on my heads right?

you shouldn't be able to notice a difference in HP or ET with rollers over stamped. the difference is more reliable operation in relation to vibration at high revs and more accurate valve opening and closing.

from what i've run into, you're fine running stock rockers if you don't spin the motor over 4500 to 5000 rpm. if you want to go any higher, get a good STEEL roller rocker. aluminum is cool and everything, it just breaks more easily under the high strains a performance cam puts on them.

I'm running an Elgin cam in my 454 with a decent lope to it (563 int ; 573 exh), since it's a street/strip car with an auto (bracket racing) i don't spin it up high enough to hurt it. my stock rockers work just fine. motor dynoed out at 517 hp with 100 octane

I will not dispute the reliability,improvement of ratios and less friction using roller rockers.

I will dispute that swapping from stamped rockers to rollers will NOT net you any ET or MPH gain.
Nothing to be gained timeslip wise

What about swapping the rocker arm OEM that are mass produced and seem to be inaccurate? Should I go with stamped steel or stamped steel roller and what brands?

Mark,I will make this statement: Everyone seems to scream about the inaccuracy of factory stamped rockers..how well do you think the aftermarket measure up for ratio accuracy? Anyone ever do any real testing? Something to ponder :)

With that in mind,stamped steel replacements are your best bet for the budget minded.

One mistake people make is using old stamped steel rocker arms with a new performance cam. The old rocker might have been used with a cam having .400 valve lift, and you put it in an engine with .450". The wear pattern between the
rocker and ball is worn for the low lift cam, and now the new cam pushes the rocker arm further and the ball hits the unworn area. Sometimes the rockers can break, and someone will say " oh you should have put long slot rockers on it"


Good words Copier !!!!! I broke a stock rocker on the way to work about a month ago. It broke across the push rod slot. Within an hour I was on my way to work again after my wife brought me a few new ones with push rods I had laying around. I hate budget so I just tonight ordered a set of Comp Cams Pro-Magnums from Summit, with new push rods