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Old 01-18-2015, 09:13 PM   #1
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Broken spark plug cover bolt

Sad moment earlier while reinstalling a cam cover. I was fastening down the cover sans flange sealant before the final reinstallation. I accidentally tightened two of the cover bolts into the hopes for the spark plug covers. One popped through the other side, breaking through the aluminum. The other bolt broke. Embarrassing.

Question is, how to deal with each of these problems?


Above is the new hole through the cam cover. I plan to add a little Curil T to the spark plug cover bolt to help seal out oil. Reasonable idea?



Above is photo of broken bolt... And the broken ez out inside the broken bolt. Question is, how critical is it to get this out and have the spark plug cover secured by two bolts vs one?
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Old 01-19-2015, 02:25 AM   #2
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Originally Posted by gonzojive View Post
Sad moment earlier while reinstalling a cam cover. I was fastening down the cover sans flange sealant before the final reinstallation. I accidentally tightened two of the cover bolts into the hopes for the spark plug covers. One popped through the other side, breaking through the aluminum. The other bolt broke. Embarrassing.

Question is, how to deal with each of these problems?


Above is the new hole through the cam cover. I plan to add a little Curil T to the spark plug cover bolt to help seal out oil. Reasonable idea?



Above is photo of broken bolt... And the broken ez out inside the broken bolt. Question is, how critical is it to get this out and have the spark plug cover secured by two bolts vs one?
You will need to drill them out and install time-serts threaded inserts.
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Old 01-19-2015, 05:02 AM   #3
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Gonzo, I have a 2.7 engine from an '01 that I am scrapping soon. If you want the cover from it PM me. The engine had a catastrophic failure and was full of debris, but I think that the cover should still be good after a thorough cleaning.

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Old 01-19-2015, 08:31 AM   #4
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Gonzo, I have a 2.7 engine from an '01 that I am scrapping soon. If you want the cover from it PM me. The engine had a catastrophic failure and was full of debris, but I think that the cover should still be good after a thorough cleaning.

STOP RIGHT THERE! The cam covers and cylinderheads on these engine's are machined as a unit; they cannot be moved from one cylinder head to another without encountering misaligned cam bores, etc. Don't even try it, it won't work.
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Old 01-19-2015, 09:06 AM   #5
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Originally Posted by JFP in PA View Post
STOP RIGHT THERE! The cam covers and cylinderheads on these engine's are machined as a unit; they cannot be moved from one cylinder head to another without encountering misaligned cam bores, etc. Don't even try it, it won't work.
I was wondering. Good to know... back in the Aluminum bin.
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Old 01-20-2015, 12:20 PM   #6
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Keep pounding against the bolt counter-clockwise with a hardened punch- it'll eventually come out.
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Last edited by woodsman; 01-20-2015 at 12:50 PM.
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Old 01-20-2015, 02:09 PM   #7
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Getting a little OT: Disposable engine...

Quote:
Originally Posted by JFP in PA View Post
STOP RIGHT THERE! The cam covers and cylinderheads on these engine's are machined as a unit; they cannot be moved from one cylinder head to another without encountering misaligned cam bores, etc. Don't even try it, it won't work.
I don't understand how with modern computer driven machining they won't make parts like this to be interchangeable. Makes me picture some guy putting the head in a vise and boring it with a big hand drill.
I will like mine 'till the engine has it's eventual catastrophic failure. I don't think the replacement engine will be an M96.
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Old 01-20-2015, 02:37 PM   #8
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78,
The continuing myth of CNC machinery is that it's more accurate than conventional machinery. All the "computer" side of the equation gets you is the ability of F up a whole pile of parts as effortlessly as a conventional machine scraps out just one.

Precision and accuracy (two different things) are still a product of machine rigidity, set up and the condition of the machine tools (cutters, drills, boring bars,etc).

I'm not a fan of the choice Porsche made to run cams right in the aluminum head without any form of bearing, and much less enthusiastic about their choice to use the cam cover as the outer bearing half. It is light, simple and cheap (to produce) however.

When they bore a head and cam cover as an assembly it doesn't really matter much if the centerline of the bore is off, say 0.005" from another head in the pile. But if you grab a mismatch set of head/valve cover and they have a 0.005" difference in the location of that bore it is a 0.005" step, and the running clearance on the cam shaft is WAY less than that (I think I saw Jake post that 0.0015" is his limit)

Props for offering up the piece though.

I'm with JFP. Suck it up and take it to a machine shop. It won't be that expensive to do a proper repair and save the valve cover.

Oh, and the M96 may have a "few" short comings but you can build up a pretty nice M96 with way less problems than the original engine and it will be cheaper than doing a full conversion using a Subaru or LS by the time you do it correctly and get the bugs worked out.

Last edited by flaps10; 01-20-2015 at 02:41 PM.
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Old 01-20-2015, 02:43 PM   #9
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Originally Posted by 78F350 View Post
I don't understand how with modern computer driven machining they won't make parts like this to be interchangeable. Makes me picture some guy putting the head in a vise and boring it with a big hand drill.
I will like mine 'till the engine has it's eventual catastrophic failure. I don't think the replacement engine will be an M96.
Then be careful which one you choose as a lot of modern engines are this way. It is not just Porsche..............
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Old 01-28-2015, 10:44 AM   #10
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Sorry to say this, but you dont have the fine touch necessary to work on these engines... It doesnt mean you never will, but working on these engines requires a lot of experience and a delicate hand. You should have felt that something was going wrong while you were tightening the bolt.

Have the dowel pin removed and the broken bolt repaired by someone with a little more exerience before you do any further damage.
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Old 02-16-2015, 09:54 PM   #11
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The EDM shop I took the part to managed to extract the broken bolt and extractor. It took an EDM drill and some follow-up with an end-mill. The shop was nice and removed the entire bolt even though all they promised before the job was that they would make me a centered hole.

Thank you EDM Labs in Fremont, CA.
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Old 02-17-2015, 04:40 PM   #12
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Glad to hear it was able to be repaired without a major overhaul.
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Old 02-17-2015, 05:26 PM   #13
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Nice. Now go forth and sin no more.
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