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Join Date: Mar 1999
Location: Vancouver,Wa.
Posts: 4,457
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Piston ID
I'm trying to identify these pistons for a friend.
My shelf of knowledge came up empty for these....try to ignore the carnage. They are Mahle 90 mm, but the valve cut outs threw me....the cutouts *appear* to be part of the orginal manufacture. What appears to be a dish in the top of the piston...is. MM is involved here so we gots a box of chocolates. On to the pics:  
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JPIII Early Boxster Last edited by J P Stein; 07-05-2005 at 02:55 PM.. |
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07-05-2005, 02:50 PM
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Location: Vancouver,Wa.
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Come on, guys. Just tell me they are standard Malhe CIS pistons that some one fly cut.
The clyinders are Alusil KS. I suspect: 1) the pistons were never ferrocoated or 2) they were used pistons that all the ferocoat was worn off. The galling on most of the P/Cs is gawd awful. This particular one took more than half the botton of its barrel off....pictures available upon request  We also gots broken rings on a few pistons.....and a real neat MM sticker on the fan shroud. ARP rod bolts and a bunch of new stuff inside the case,seals, chains, yada.....looks like it only ran once....and not for long
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JPIII Early Boxster |
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07-05-2005, 05:45 PM
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I would rather be driving
Join Date: Apr 2000
Location: Austin, TX
Posts: 9,108
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Just like you said. They look like a CIS piston that had valve clearance pockets cut.
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Jamie - I can explain it to you. But I can not understand it for you. 71 911T SWT - Sun and Fun Mobile 72 911T project car. "Minne" - A tangy version of tangerine #projectminne classicautowerks.com - EFI conversion parts and suspension setups. IG Classicautowerks |
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07-06-2005, 07:21 AM
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Irrationally exuberant
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Out of curiousity, what is the top ring thickness? MM has been known to "recycle" pistons by cutting new wider ring groove and using a thicker ring. I think Mahle did this for a friend of mine once.
Don't CIS pistons tend to be low compression? I would think that cutting a valve relief pocket in a CIS piston would make the compression so low as to be unusable. Just speculation of course. -Chris
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'80 911 Nogaro blue Phoenix! '07 BMW 328i 245K miles! http://members.rennlist.org/messinwith911s/ |
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07-06-2005, 07:53 AM
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i'm suprised MM didn't weld up the dished part to make up for the lost compression
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big AL '77 911 |
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07-06-2005, 02:44 PM
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The piston ring grooves (those that survived the disaster) are un-cut. It looks like they actually did a decent job on everything but the P/C mismatch. 4 of 6 are galled.
The case was line honed, main bearing wear (for it's short life) looks like the case was pretty straight. The bypass mod was done, time certs in, ARP rod bolts, std/std crank, new chains, seals & all....to bad somebody screwed the pooch on the pistons. Oddball non CIS/MFI heads that someone ported to 36mm on the intake side only. Haven't got the cams out yet to see if the fly cuts were necessary.....A lot of work that was wasted cause someone was stupid/ignorant. A  waiting to go off
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JPIII Early Boxster |
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07-07-2005, 09:51 PM
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The Blue Pheonix
