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Join Date: Mar 2003
Location: Edmonton
Posts: 549
NOS cams vs billet; plus rockers

For the same price, would you go with NOS cams or new billets? 'E' profiles. And for this relatively mild profile is it OK to reuse used rockers?
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Matt B
'73 911E
Old 04-09-2019, 02:25 PM
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Join Date: Mar 2004
Location: Windsor, CT
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A good nos cam should be just fine. If that is the profile you want.

Used rockers is a bad idea. The bore of the soft bushing wear at an angle. The resulting wear means the rocker pads were aligned with the specific cam tower and individual rocker shafts and the old cam surface.

The new cam will likely suffer from uneven wear and probably start to fail (spall) the rocker pad surface. This will happen quickly. And then the nos cam will need to be reground, or replaced with a new “billet” cam. 🙁

And the rocker may (will) also start to chew up the rocker shafts if they are not smooth.

I’d have the rockers rebushed and reground. Polish the rocker shafts smooth or replace them.
Old 04-09-2019, 04:04 PM
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The resulting wear means the rocker pads were aligned with the specific cam tower and individual rocker shafts and the old cam surface.
Assuming the bushing is in good shape, aren't these all parallel? I don't imagine the cam lobe has any taper.
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'73 911E
Old 04-09-2019, 04:19 PM
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The bushings do not wear perfectly. They have a slight bias. The valve is centered in the head and the two lobes intake and exhaust, are offset to fit

That offset creates a torque on the rocker during operation. And wears the bushing unevenly.

And causes a slight taper wear pattern on the rocker face.

All of this means old rockers on new cam shafts are not going to be happy.

Also, the wear pattern on the rocker is specifically matched to its cam lobe. You can see it in the surface of the rocker. If the new cam and rocker mate up at a different location then the surface may have a ridge or valley that gets crossed over each time. Oil, may /may not like to maintain a lubricating film over that transition.

If you Reuse the old cam, with the rockers and shafts from the original positions. Installed in the old cam tower. That is ok.
Old 04-09-2019, 05:09 PM
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gearhead
 
Join Date: Nov 2007
Location: Loverland, CO
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Send your rockers off to Steve at Rennsport Systems for reconditioning Or try Jeff at Turn3 in BC if you don’t want to deal with shipping Parts across the border.
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Old 04-10-2019, 08:26 AM
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I sent my cams and rockers to John Dougherty Racing. Cams ground to DC30-mod Solex, and he rebuilt the rockers (rebushed and ground face) for 38.00/rocker, under $500. I thought that was a great price and service.
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Old 04-11-2019, 05:47 AM
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Cgarr (Craig Garret) in Grand Rapids does a great job on rocker refurbishing.
Old 04-11-2019, 07:58 PM
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