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911TE's Avatar
 
Join Date: Nov 2004
Location: Munich, Germany
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hair cracks in 993 heads

In cleaning and bead blasting the heads of my 993 engine I found in every head a very small crack beginning in the threads of only one spark-plug to the exhaust valve seat.
Has anybody here, especially the profi head rebuilder seen this before?
Can I reuse these heads with new valve guides and ignore the cracks or will finally the seat-rings fall out?

Sebastian
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Old 03-03-2006, 07:10 AM
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I have a set of 993 heads if you need them.
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Old 03-03-2006, 08:55 AM
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I'd take them to an experienced machine shop that has dealt with 911 engine parts before. They will be able to advice whether this can be repaird.
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How about a NoBadDays DualChip for 964 or '95 993
Old 03-03-2006, 09:14 AM
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Paul, thank you for the offer, I`m only afraid shipping them to Germany wouldn`t be cheap. If the experts say they are crap, IŽll come back to you!

ischmitz, IŽve been to my machine shop, he is able to repair them, but this would mean pulling the valve seats, welding, cutting new threads for the plugs, machining for over-size valve seat and pressing in new seats, probably more expensive than used heads.
The machinist says, there are a lot of cylinder heads of other brands where cracks are standard and do not harm, he just doesn`t know how Porsche 993 heads behave!

Sebastian
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Old 03-04-2006, 11:51 AM
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hallo
i send you a email ,i have aset of 993 heads .
harald
Old 03-04-2006, 12:07 PM
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Hi Sebastion, Shipping by US Mail is cheaper than you might think and only takes a week, I ship Porsche racing engine parts to Europe quite often.
Thanks, Paul Weir
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Old 03-05-2006, 07:44 AM
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Paul and Harold,
I know you guys must have seen a lot of 911 heads. I'm curious, what is your experience with 993 head cracks or 911 head cracks in general?
-Chris
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Old 03-05-2006, 09:27 AM
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The only cracked 911-930 heads I can remember seeing came off 935 and 962 IMSA engines where the boost was turned way up.
I have a few cracked 3.8 RSR heads an a few cracked 993 heads but I am sure they came off full race engines so its more understandable.
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Old 03-05-2006, 10:56 AM
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Harald please respond to my emails.
Thanks
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Old 03-06-2006, 01:19 PM
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I attach a picture of the crack, highlighted with green color, otherwise it wouldn`t be visible on the picture.

Any comments?

Sebastian
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Old 03-06-2006, 02:43 PM
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it would probably be cheaper to start with a good set of used heads than repair those. remove seats, weld, remachine, install new seat X 6 wouldn't be particularly cheap. seat swapping in 911 heads is dicey. i've seen too many replaced seats come loose.
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Old 03-06-2006, 04:40 PM
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Are these the 914 heads of the future? I wonder if we will start seeing more of this....


Cheers
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Old 03-06-2006, 06:45 PM
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We made a test today at the machine shop, heads were heated in the oven to 300 degrees Celsius=572 degrees Fahrenheit, the exhaust rings are still firmly in the heads. I think I will leave them in and hope!

Sebastian
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Old 03-07-2006, 07:50 AM
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