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Registered User
Join Date: May 2013
Location: Western Massachusetts
Posts: 5
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1981 911sc need advice
My girlfriend inherited a 1981 911SC. This car sat for several years. I charged the battery, changed the fuel pump, flushed the gas tank,and replaced a brake line. All I had left to do was replace leaky valve cover gaskets and change the oil. As I began replacing the lower gaskets I found 10 of the 12 lower head studs broken.
After removing the motor and purchasing Bentley's Porsche repair manual I began to disassemble the engine. After disassembling down to the case I successfully removed all 12 lower studs. The only problem I have is I removed the cylinders from the pistons. Is there any way I can re-ring these pistons and reuse the cylinders? I found out after the fact that I should have removed the wrist pins. Too late for that now. The pistons and cylinders are Mahle's. They look good there is no damage to the cylinders. The odometer reads 112,700. |
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05-29-2013, 04:16 PM
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Registered
Join Date: Mar 1999
Location: Des Plaines, IL USA
Posts: 79
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I'd suggest getting Wayne Dempsey's book, How to Rebuild and Modify Porsche 911 engines. There's a lot more involved than rebuilding a SBC, and some special tools are needed.
As far as the broken studs, the engine had Dilivar studs originally, and these are known to fail as you have seen. A good alternative is to replace them with those made by Supertec or other aftermarket manufacturers. As far as reprinting the pistons, you need to check the wear specs on the pistons and cylinders to let you know if they're still OK. I'd also take a careful look at the valve stems to see if they're still within specs or need replacement. Enjoy your project in good health! |
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05-29-2013, 05:07 PM
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Free minder
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You are lucky because Mahle cylinders are better than Alusils cylinder for reringing. At 112,000 miles, I would do it. The recommended preparation method for the cylinders is to deglaze them with a 3M red scotch Brite pad on a hone. Do not use the hone diamonds directly. Just 3-4 vertical motions should be enough to help the rings seat. Then break in method is important too, up and down rpms. You can get away with just replacing the rings and headstuds, although now would be a good time to renew the heads too...
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1978 SC Targa, DC15 cams, 9.3:1 cr, backdated heat, sport exhaust https://1978sctarga.car.blog/ 2014 Cayenne platinum edition 2008 Benz C300 (wife’s) 2010 Honda Civic LX (daughter’s) |
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05-29-2013, 08:36 PM
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Registered User
Join Date: May 2013
Location: Western Massachusetts
Posts: 5
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Thanks for the advise
I appreciate your advise. I will purchase Wayne's book and I need to know where to get the rings if the cylinders and pistons are within specs. So far as purchasing the special tools required after spending hours reading this forum I have no problem spending the money. Does anyone have preference on what brand tools works better? I am a heavy equipment mechanic so I deal with Snap On and Matco regularly. No Mac dealers left around here.
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05-30-2013, 03:13 PM
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Free minder
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Quote:
Porsche 911 & Carrera Pistons, Cylinders, and Heads - Page 2 Snap on tools have an excellent reputation. But it is the part that hold the tool which matters most  .
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1978 SC Targa, DC15 cams, 9.3:1 cr, backdated heat, sport exhaust https://1978sctarga.car.blog/ 2014 Cayenne platinum edition 2008 Benz C300 (wife’s) 2010 Honda Civic LX (daughter’s) |
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05-30-2013, 04:22 PM
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Registered User
Join Date: May 2013
Location: Western Massachusetts
Posts: 5
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No truer words have ever been spoken
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05-30-2013, 04:30 PM
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