forged rockers - friend or foe?

[66S]

Are the early adjustable forged rocker arms good for racing? Im assuming the racing rockers are also forged. Ive been told cast rockers will work for racing but X-ray them first. What do 911 racers use?

[tom1394racing]

Many racers use them because of the added strength.

The problem with them is that they are too strong. In the case of an over-rev situation, where the pistons and valves come in contact, the cast rocker will break and limit the engine damage while the forged will not and something else gets damaged like a valve or a piston.

I recent parted out an early Al case motor that had been over-reved. Every piston had a deep impression from the valve and one piston pin was broken from the impact ruining that piston and cylinder. All the rockers were in tact with no impact damage.

[a911s]

Grady Clay told me the same thing. Nice and strong, but they are a b**ch to adjust and will not break before the valve damages the piston. They are nice but not necessary for an 8500 rpm motor that has all the other good stuff, so I went with polished forged that were inspected.

[kenikh]

The forged have a (minimally) better rocker ratio than cast.

[Steve@Rennsport]

Forged rockers are slightly lighter and do raise the threshold of valve float (much like RSR ones do) but like Grady said, they will not snap off if the valves collide with the pistons.

That said, I've seen PLENTY of bent valves using the cast rockers so its no guarantee they will break off to save the valves & pistons,...

I have no qualms about using them provided they are in excellent condition and good aftermarket valve springs & retainers are installed.

[304065]

Steve, what did we ever conclude about the rocker face? How could that be renewed? I think you said it was hard chromed?

I have a set from the '66 resting in eternal slumber in cosmoline, along with the shortie rocker shafts with the 5mm pinch bolts.

Did we ever validate the rocker arm ratio by an objective measurement? I've heard they are a fraction better, but wonder 1) where on the rocker face that calculation is performed, or is it an average and 2) what is the methodology for that test. Seems to me that the geometry of the stock cam tower is the limiting factor but what do I know, I just read a lot.