Forged Rockers

[chris_seven]

I am planning to order tooling to re-manufacture a drop forged Rocker for the 911 engine.

I would prefer forged rockers in race engines and for Period F FIA engines the 'solid' Motorsport Rocker that is being remanufactured in UK is not allowed and too expensive.

The plan is to make a batch of Rockers from 4340 and supply them with a new Elephant's foot.

They will have a DLC coating rather than hard chrome.

I haven't got final pricing but they shouldn't be out of reach.

[Chuck Miller]

chris,

You’ve probably taken this into consideration but………

Please double check the surface 'Rockwell' of your proposed rocker to make sure they will be compatible with some of the 're-grinds' we use. Example, WebCams lobe surface is much harder than the factory's.

[YTNUKLR]

How will that be allowed if the other repros are not?

[chris_seven]

The RSR style rocker doesn't have any adjustment hence it was described as a 'solid' rocker. To adjust valve clearance you have to fit a 'lash' cap that is specifically ground to the correct size or have a bucket full made with different heights.

These Rockers are specifically forbidden by FIA for Period F Appendix K cars, which is my main interest in making these parts. They are also about $500 each without the lash caps. !!!

Our plan is to replicate the 1965 and 1966 forged rockers which take a standard Elephant's foot adjuster and hence are quite acceptable for all periods. They are also much easier to install and set up than the solid type.

Chuck, A DLC coating is extremely hard and wear reistant it is difficult to measure the hardness of these thin coatings but some recently developed techniques seem to indicate figures of around 1800Hv can be obtained.

The surface has a very low coefficient of friction and wear is generally excellent.

it is also reported that these coatings have no impact on fatigue life and they are tinn enough to be able to be applied to the complete component wiithout the need for any masking.

The majority of rockers used in F1 engines have used this type of coating for several years now so I am reasonably confident that they should work well.

[preS]

I had this discussion last week w/ Scott (Kinder). Have you ever had a later rocker break under normal circumstances but high revs, like 8200 rpm?

Richard

[Alan.uk]

Hi Chris,

I have also considered having these made, but if you do it, I would be a customer. Please keep us up to date. Depending on price I would need enough for 3 engines.

Alan

[chris_seven]

Richard, I have had two cast rockers fail in fatigue but they were standard and hadn't been shot peened, which may give an improvement but we just don't have the resources for testing. A retirement from a single race will lose almost as much money as the tooling cost so I think that to have a forged rocker is a reasonable insurance policy.

I have seen some 964 rockers used in race engines - they have been extensivley modified to take an Elephant's foot and these are being used in a number of early race engines but th cost is horrid at over $650 each!!

I hope to produce good rockers with the correct metallurgy and heat treatment for within 20% of the price of a factory cast rocker.

[Flieger]

I applaud your efforts, Chris. I always thought the forged rockers just looked more finished and well engineered compared to the cast rockers. I never really bought the "sacrificial rocker arm" explaination. It seems if the valve took enough force to break the rocker, there would be other damage as well. The forged must be lighter, as well, without all that flash.

If I was building my motor, I would use a set. But, I will run what I have for a while.

[preS]

It seems if the valve took enough force to break the rocker, there would be other damage as well

Often the valves are just slightly bend at most and at least you can continue w/ min time losse in for instance an endurance race or rally. An overreved engine w/ forged rockers is end of the race / rally.

Richard

[Chuck Miller]

I commend Chris’s efforts as well

However Richard has a point......

I drove my car for 3 months after zinging it at the track .....
At the rebuild the only way you could tell the 2 bent exhaust valves were bent was to spin'm on a lath and take a very small bite.

...... these engines REALLY want to keep run'n give'n half a chance.....