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Can anyone id these rocker arms?

These are out of my 930 engine. While giving them a pre-cleaning treatment before re-bushing and re-grinding I noticed I have 3 different types or brands of rocker arms.

The first one on the left and the center one are very similar. While there are very much alike, the one on the left has a rougher casting finish than the one on the center. There is also the letter "B" cast into the side. I only have one of these.

The middle one has a much better finish than the others and appears to be factory original. I have 8 of these.

The one on the far right also has the letter "B" cast onto the side and it's missing the little "ridge" feature on the threaded size of the rocker arm. This one has the worst casting finish of all three.

Can anyone shed some light on these?




Old 10-24-2010, 05:32 PM
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Same parts, but made by different vendors to Porsche A.G.

The QC on rockers has really slipped over the years and we have to check each one to make sure the bores and pad surfaces are parallel.
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Old 10-24-2010, 05:43 PM
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Thanks Steve, I am really surprised that they are all factory rocker arms. Especially the one on the far right.

It really makes me wonder if there are any other differences I can't see or measure between these.

I would sure feel better if they all matched.
Old 10-24-2010, 06:23 PM
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I just looked at my 50+ core rockers and could not come up with a perfect matched set!

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Last edited by cgarr; 10-24-2010 at 06:44 PM..
Old 10-24-2010, 06:33 PM
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Quote:
Originally Posted by nocarrier View Post
Thanks Steve, I am really surprised that they are all factory rocker arms. Especially the one on the far right.

It really makes me wonder if there are any other differences I can't see or measure between these.

I would sure feel better if they all matched.
Yes indeed, those are all OEM pieces made by different manufacturers to Porsche.

As above,...each & every rocker arm used in all of our engines get checked for parallelism. Rockers used in race engines get magnafluxed (and sometimes X-rayed) for cranks and occlusions.

Many years ago, a gentleman named Clay Dopke used to sell rocker sets that were X-rayed, magnafluxed and then fully polished to eliminate stress raisers. Not cheap, but they were very reliable.
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Old 10-24-2010, 06:55 PM
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I guess there are a lot of engines running out there with mixed up rockers!

I think I am going to try and find 4 more of the ones like the center one in the picture.

The ones on the right are terrible compared in person .
Old 10-25-2010, 07:20 AM
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Here's four different styles:



From my fleet (which is now larger by about 11):



Old 10-25-2010, 11:49 PM
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Do I recall that the un-bushed rockers (red arrows) were only on some ’68-’69 cars, starting with the RoW ’68 911T?

If so, how did these get in a 930 engine?
Could this be a MM ‘back-date’?







Best,
Grady
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Old 10-26-2010, 12:12 AM
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No, sorry for the confusion. I am getting them re-bushed and re-ground. A friend of mine had a valve grinder but I just found out it's long gone..... I had made a tool to press them out so I just went ahead and did so.

On another note, this engine is a complete basket case! I ended up buying the car from a customer of mine who supposedly just had the engine rebuilt from a shop in central Florida. He shipped the car to me sight unseen to see if I could sort it out. (I have never met him in person) After a few months, and of me telling him that my impression was he got the "short" end of the stick, he asked if I wanted to buy the car.

Knowing I would have to do a complete rebuild, (and the fact that I have loved this car since my previous life) I offered him a reasonable offer which he took! Other than the fiberglass 965 style bumpers, and rockers, the chassis is nice and clean. (I am going to return the body to stock. I don't feel safe with fiberglass parts on a street car.

I actually found a very large receipt in the glove box from a shop in central Florida.

I attempted to contact them before and after I bought the car but I get no response (go figure).

On a supposedly fresh rebuild, all the rocker arm bushings were out of spec as well as the cylinders, valve guides, a few seats, valves. The timing chain was not adjusted properly and the sprockets and chain were chewing themselves to an oblivion! I am almost ready to split the case. I have already removed the number 5 Rod and thankfully, the bearing was a std. size!
Old 10-26-2010, 05:00 AM
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Rockers

Who's shop, or what city was the shop in if you don't want to disclose.
Mike
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Old 10-26-2010, 05:21 PM
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The shop with the large receipt is in Sebastian, FL

But get this,

I have a receipt from another shop in W. Melbourne and one of their line items is

" Replace fuel distributor with US version."
Old 10-27-2010, 07:13 AM
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We are North of Orlando, and I'm not sure who is over there in that area, let me know if I can be of help

Mike Bruns JBRacing.com
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Old 10-27-2010, 07:18 AM
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Rocker arm ID:

At Gunnar Racing's website; "Did You Know?"
Gunnar Racing, they posted a picture of some rocker arms:


... but without an answer. Can anyone fill in the missing info?

In Early rocker arms
Grady has this to say:

"There are four distinct rocker arms:
There are the original forged steel rockers with bushings used ’65 through some ’68.

There are the cast steel, non-bushed rockers used in some ’68 and later.

There are the cast steel, bushed rockers used from ’68 all through the later 911s. Many, many years.

There are the forged steel non-adjustable rockers initially used in the 906 and 911R, 935 and all through 962. These racing parts require a ‘lash cap’ on the end of the valve stem to adjust the clearance. Adjustment is with swapping different ‘lash cap’ thickness.

The forged steel rockers are stronger and the non-adjustable ones also much lighter allowing much higher revs. On a street (and weekend track car) that is a disadvantage. Many use the bushed cast steel rockers for safety. If over-reved and the valves contact the pistons, the rocker will break, possibly saving further damage."

Can anyone match Grady's description with the above photos? Grady?

Thanks,
Sherwood
Old 06-19-2011, 11:59 AM
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bump
Old 06-27-2011, 08:34 AM
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Is it common the rockers to break?
I have a friend with a 964 RS with slightly hotter cams and stiffer valve springs to match.
2 of his rockers broke on the same cylinder at the same time (well, guessing on that). The engine wasn't overreved, they broke coming out of a corner on the track.

He just put in 2 new rockers from Porsche, which by the was looked like cheap china knockoffs, and the engine was back to normal.


Sorry for the hijack...
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Old 06-28-2011, 07:35 AM
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the only porsche shop i know of in w. melbourne is the werkshop. hope that is of help.
The Werkshop - Home Page
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Old 06-30-2011, 06:14 PM
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