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Join Date: Nov 2008
Location: Michigan
Posts: 642
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Can I glass bead my Heads?
Last fall, I found 3 broken head studs on the left bank on my SC. I removed the head about a week ago and saw what was happening. Everything looks alright other than some scaring were the sealing ring moved out of the grove in the cylinder and got pinched a few times agianst the combustion chamber in the head. It seams to be relatively light but was wondering if glass beading an aluminium head is safe or not. Thanks.
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04-19-2010, 01:20 PM
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Senior Member
Join Date: Feb 2000
Location: Lacey, WA. USA
Posts: 25,310
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Yes, I have seen glass-beaded heads. Once they are cleaned up, inspect them carefully. It sounds like they are damaged. If you look carefully on the surface that touches the tops of the cylinders, and if you see that the cylinder has left a mark of any kind, that means your head has been beating agains the top of the cylinder and is no longer flat. I had my heads fly-cut when they were off for a head stud repair.
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Man of Carbon Fiber (stronger than steel) Mocha 1978 911SC. "Coco" |
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04-19-2010, 02:49 PM
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Location: Cridersville, OH
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Yep, just clean them good with hot soapy water afterwards and then machine.
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75 911 Indian Red- RUFWAN2B 2000 Boxster 2000 & 2007 Dobies www.stahlwerks.com Cages and preparation for your Porsche “People who never make mistakes must get tired of doing nothing” Bill : The origin of the orgy of Porsche |
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04-19-2010, 03:10 PM
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I don't see any marks where the cylinders have been baning on the heads, just some scaring from the sealing ring around were the ring meets the head.
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04-19-2010, 03:32 PM
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Heres a pic of what I got. I think just a good beading would clean this surface right up. You can feel it with your finger, but it isn't real deep. I'm a machinist so I'm used to feeling .005 differences in surfaces so I can feel it well, but doesn't feel to damaged. What do you guys think?
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04-19-2010, 03:48 PM
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I think you're going to take more than .005 off to clean that up. That's what I think.
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75 911 Indian Red- RUFWAN2B 2000 Boxster 2000 & 2007 Dobies www.stahlwerks.com Cages and preparation for your Porsche “People who never make mistakes must get tired of doing nothing” Bill : The origin of the orgy of Porsche |
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04-19-2010, 04:19 PM
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Join Date: Mar 2001
Location: Marysville Wa.
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those swirlies are from the head gasket inner windings blowing out and getting pounded between head and cylinder. i would recommend having them all flycut. that does not look good. once they're glass beaded, you will see more. then there's the matter of the cylinder top edges that get pounded just like the heads. a good machinist can do a slight cleanup cut on those also, so you get a decent seal all around and no seepage, (fluid or compression).
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04-19-2010, 04:29 PM
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John, is it true that the head sealing face is machined with a slight taper, maybe a thousandth or two?
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2014 Cayman S (track rat w/GT4 suspension) 1979 930 (475 rwhp at 0.95 bar) |
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04-19-2010, 04:35 PM
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Location: Nash County, NC.
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In my experience when there is broken studs there is a tenancy for the heads to warp and requiring fly cutting as part of the valve job completion.
Bruce |
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04-19-2010, 05:18 PM
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1979 Porsche 930 3.4
