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len911's Avatar
 
Join Date: Feb 2002
Location: Central NJ
Posts: 568
2.7 Piston carnage...

Well, I'm slowly getting into the 2.7 out of the 76 I bought a couple of months ago. Engine was smoking consistently, low compression on most cyls. PO said that it started smoking after he installed the dist 180 deg out of phase...

Well, I think something was dropped inside the cylinder. What do you guys think of this damage. Looks like there are two piston chunks missing, along with cyl wall scoring. Also, the head took a beating... Will eventually need a new head and cyl.

Did 2.7 come with Mahle cyls? I counted 11 fins and the base of the cyl has the "m" next to the triangle with the cyl height and size tolerance... Lou

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Old 02-14-2006, 07:04 PM
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put a magnet on the cylinder wall. If it slightly sticks it is a nikasil if not
it is alusil
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1976 911s targa
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Old 02-14-2006, 07:13 PM
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The color of the cylinder looks like Alusil. The magnet test will tell more. If it's Alusil you should be able to find another cylinder cheap.

-Andy
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Old 02-14-2006, 07:38 PM
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Looks like the classic hole in a piston. Typically detonation cracks the area above tht top ring groove, pieces fall out and bounce around in the cylinder until being expelled through the exhaust. Less severe cases would just show a burned notch in the same area and no head damage.
Phil
Old 02-14-2006, 08:49 PM
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that doesn't look too bad at all

you should have seen the piston that was hitting this...
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Old 02-14-2006, 10:27 PM
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Naah, it looks like knock induced cylinder erosion to me. Eroded piston edges w/o marks in the middle is a tell-tale.
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Old 02-15-2006, 02:26 AM
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Quote:
Originally posted by obrut
that doesn't look too bad at all

you should have seen the piston that was hitting this...
DAYUMM! This made me wince and cringe!
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Old 02-15-2006, 03:14 AM
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sand man

motor failed day 1 of a 4 day rally. over-rev lead to bent valve which then broke and the valve head dropped into the comb'n chamber. it all went pear shaped about 200m from the end of the last stage of the day. not what you call a good day...

however, the rebuilt motor is even better...

len911 - sorry about the thread hijack!
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Old 02-15-2006, 03:32 AM
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