Advice on reconditioning rocker arms

[Swallowtail]

Hey guys,

I’m not sure about the options regarding my rocker arms of my ’73 911t. To me it looks like they have been reground in the past. However some of them show some pitting.

Here is a picture of the worst offender and what I consider to be the best one. The rest are somewhere in-between.

Is the pitting normal or is this a sign of some mistake in the past? Do I need to replace the arms or is there enough material to have them ground back to spec?

The bushings look perfect by the way. Haven't had a chance to measure them.

thanks,
Andy

[Flat6pac]

The condition of the rocker makes it impossible for it to do the job it was designed to do?
Removing metal won’t change the charistics of the design?
Bruce

[stownsen914]

The pitting could be from abnormal wear, or inclusions from casting. It would take a lot of grinding to remove those, so that rocker is probably toast.

How's the cam look?

[Swallowtail]

According to my machinist the cams look like they have been reconditioned in the past but are in excellent condition. If I have time later maybe I will take some pictures.

[cgarr]

If I had to reconditioned those I would grind it clean then heat treat then finish grind it.


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[Swallowtail]

Originally Posted by cgarr

If I had to reconditioned those I would grind it clean then heat treat then finish grind it.

By heat treating you mean hardening or stress relieving? As I understand, they were never hardenend by the factory. If I read your signature correctly you do this professionally. So in your opinion they have enough meat to be saved?

[cgarr]

Well someone flame hardened the cast iron surface

Should be able to save them, they are only surface hard to about .030 so if you grind out the pitting you should harden them again


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[stownsen914]

^^ there's an expert opinion

[Rosco_NZ]

WebCam can weld and regrind.

[winders]

Originally Posted by Rosco_NZ

WebCam can weld and regrind.

^^^^ Ding, ding, ding! We have a winner!!!

[Neil Harvey]

Some cautionary advice for free.

Make sure that the dimension from the pin centerline to the pad radius center point remains as designed. Otherwise your camshaft geometry will be wrong and the engines performance will suffer.

Also, make sure that the rocker pad surface hardness is softer than the cam lobe. Not sure if a welded surface is correct here???? May look good when finished but could be an issue when running.

[911pcars]

Originally Posted by Rosco_NZ

WebCam can weld and regrind.

A question would be if Webcam requires new or rebuilt rockers With their new or remanufactured cams (possibly all welded lobes). Factory cams are cast iron that are surface hardened.

Rocker arms and cam lobes must be compatible.

Sherwood

[Swallowtail]

Thanks guys, I will phone around in Germany for a viable repair option. Otherwise I will have to bite the bullet and buy a new set

[mikedsilva]

Originally Posted by 911pcars

A question would be if Webcam requires new or rebuilt rockers With their new or remanufactured cams (possibly all welded lobes). Factory cams are cast iron that are surface hardened.

Rocker arms and cam lobes must be compatible.

Sherwood

This is an interesting question. I did run a new Webcam with some reconditioned rockers not long ago, and the rockers started pitting again. I have not spoken to Webcam to ask if they have any specific requirements.

I only happened to notice the pitting by chance but it prompted me to check them all.

[reclino]

What type of oil are you running with the pitting on the rockers?

[911pcars]

Originally Posted by mikedsilva

This is an interesting question. I did run a new Webcam with some reconditioned rockers not long ago, and the rockers started pitting again. I have not spoken to Webcam to ask if they have any specific requirements.

I only happened to notice the pitting by chance but it prompted me to check them all.

My question is answered by my last look at Webcam's website. They suggest new or their refurbished rocker arms for their new or "rebuilt" cams. Welded cam lobes are harder than ground cast iron.

Sherwood

[Neil Harvey]

Originally Posted by 911pcars

My question is answered by my last look at Webcam's website. They suggest new or their refurbished rocker arms for their new or "rebuilt" cams. Welded cam lobes are harder than ground cast iron.

Sherwood

Correct, be sure you know what the matching hardness levels are. But I don't agree with welded rocker arm pads. Just my opinion and not how we do this. If others do this hand they work , then there are many ways to do this work.

The first and most important factor to consider is the final geometry. There is some allowance to regrind the face pads and stay close to the original designed geometry. The depth of the hardness is another factor that has been brought up in a previous post.

The bushings should be replaced and honed with the correct pin fit to a new or near new shaft before any work is performed on the pad face. The rocker arm should be measured on a jig so the geometry is known. This will show if the pad faces have already had work done to them. If the geometry is off, we have the faces hard chromed, a known hardness and then re grind the faces back to the original geometry.

This gets expensive when you see what a new rocker arm costs. We have been doing this for many years and include DLC coating of the rocker arm and shaft to limit future wear.