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Cam tower resurface

Anyone ever have their cam towers resurfaced? is it common to do during a rebuild to help eliminate oil leaks?

Thanks
Old 07-31-2016, 11:30 AM
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I mean the cam tower to head surface
Old 07-31-2016, 12:22 PM
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Old 07-31-2016, 01:17 PM
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Originally Posted by john walker's workshop View Post
No.

Dang. .040 off both sides. Looking back at stuff I did in my 20s is difficult sometimes.
Old 07-31-2016, 03:40 PM
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0.040" seems like a lot. Did someone gouge them with a chisel when separating or the like? They are not wear surfaces.

I would expect that you might have to shave the chainbox ends by this amount so that the cam seal will fit properly. Maybe you could just dispense with the gasket between chain box and case? There is some room for misalignment there, but not a lot.

In addition, your chain will seem to be too long, although you can get idler gears which are a larger diameter than stock to help with the slack there - because the chain tensioner system can only deal with so much slack in the chain before you start to run out of travel.

Plus your rocker arms will be at a different angle, though I suppose you won't run out of adjustment of the elephant feet, and maybe these angle changes won't cause problems like excess side loading on the valve stems leading to accelerated valve guide wear. The rocker surfaces which bear on the cam might wear over a slightly different section of the rocker, but if they are new or reconditioned maybe that won't matter, although I suspect there would be a small change in the effective rocker ratio.

Are good used ones expensive these days?
Old 07-31-2016, 06:16 PM
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Oh - you could use thicker cylinder base shims to get the geometry back to normal, but you'd reduce your compression. Unless you use aftermarket pistons cut to have a bit more than stock.
Old 07-31-2016, 06:18 PM
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The motor was rebuilt 12 years ago. I put a couple hundred miles on it, lost my job, big changes happened in my life and the car sat in storage for the next 10 years. Things finally settled down, I bought a house and I've been tinkering with the car this summer. It's not running very good so I'm thinking about all the mistakes I probably made during the rebuild. I was in my early 20s when I finished the motor.

It's a 2.2 rebuilt in a 7R case, JE 10.5:1 pistons and 1966 L cams. Hydraulic tensioners all that new stuff... I think I was overly paranoid about oil leaks back then which is why I had the cam towers milled down flat. Though I will say it doesn't leak any oil at all.

It runs ok as long as your foot is on the floor. It won't idle for squat.
Old 07-31-2016, 07:13 PM
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Twin plug? 10.5 is too much for street gas without it, even with a really hot cam. Is the L like the 906 cam?
Old 07-31-2016, 09:10 PM
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My plan now is to put 5 gallons of avgas 100 low lead in it every fill up. I seem to remember there being 94 at the pump years ago.

I recall the 1966 L cam being between an E and S but I can't remember now.
Old 07-31-2016, 09:41 PM
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Ask Henry Schmidt at Supertec if he can set you up with some cam housing shims. I've seen him post pictures of them here in the past.
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Old 08-01-2016, 07:33 AM
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Also, I think these housings are not all that stable dimensionally. I've put a few junk ones on a flat piece of glass or a large hunk of quartz (taken from a rehabbed kitchen) and they take a bit of sanding to get the surfaces level. John @ Costa Mesa R&D seems to think they need a resurface. But I think he's also doing that along with some other fixes to later 993 type housings.

https://www.youtube.com/watch?v=PTxkj1QkCYY

https://www.youtube.com/watch?v=aWLsKUJCy0A

All that said, I think their dimensional instability allows them to twist into shape when mounted on the heads? I don't know about that. but I do know it's not unheard of for a cam to bind inside the housing
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Old 08-01-2016, 07:38 AM
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We recondition the cam towers on every rebuild we do. That includes surfacing them.
Generally .005" will bring them around. "040" seems excessive.
Used or reconditioned cam towers are fairly reasonable (in the overall scheme of thing) so when in doubt, replace it.

Ken @ 911 Vintage Parts sells used and reconditioned cam tower for all air-cooled Porsche engines. info@911vintageparts.com

760-731-4911


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Old 08-01-2016, 07:50 PM
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