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Registered
Join Date: May 2003
Posts: 132
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98 mm cylinders, O-ring or Gasket?
I just bought a set of 98 mm Mahle cylinders with RUF pistons. The cylinders have been cut for a gasket or an O-ring. Can anyone give me some insite on this modification?
Do I have to o-ring the heads or can I use a head gasket similar to the 3.0 liter 911? Does anyone know of a source for the head gaskets? Pelican does not have them. The measurements are ID = 4.045 in or 102.743 mm depth = .074 in or 1.880 mm width = .084 in or 2.134 mm OD = 4.213 in or 107.010 mm Here is a close-up of the groove  Vic
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Victor Toce 2000 Boxster S w/ Tequipment exhaust 1993 Spec Miata 87 911 turbo - sold 3.4 RUF pistons and cylinders Euro CIS head |
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03-09-2004, 05:17 PM
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Forced Induction Junkie
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Victor,
The cylinders have been "Ni-Rist"-ed. This machining process improves the sealing between the cylinder and cylinder head under high boost pressures. Both the heads and cylinders have to be machined to accept the Ni-Rist rings. I recommend you take both the cylinders and heads to a Porsche machine shop so they can match up the correct rings.
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Dave '85 930 Factory Special Wishes Flachbau Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P |
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03-10-2004, 08:03 AM
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Registered
Join Date: Mar 2002
Posts: 3,563
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Vic,
LUCKY YOU! Dave is correct, these cylinders have been prep'd for Flame Ringing. Protomotive typically does this mod/upgrade to it's HIGH HP beasty creations. Send your heads to Todd Knighton of Protomotive and have them match machine them for these cylinders. They will also make up the Aluminium rings which slot into this groove to provide you with exceptional cylinder-head sealing at high HP/boost levels. You won't see any cylinder-head leaks for up to 2.0+ bar boost levels  This is the sealing technique they use for their Stage 4 turbosystems, which run 1.25-1.4bar 
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Merv '89 911 Turbo Cab Protomotive MAP ECU, Twin Plugged Heads, GT2-EVO CAMs, 3.3L fully finned P&C's, ARP fasteners, C2T head gaskets, Titanium Retainers, Turbo spec valves, springs & guides, 964 splash valves, GT35R BB turbo, GSF Stainless Headers, Magnaflow Exhaust, Full bay Intercooler, TiAL 46mm w/gate, TiAL 50mm BOV, Apexi AVC-R EBC, SPEC Stage3+ Clutch kit, Crane CDI Ignition 
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03-11-2004, 06:17 PM
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Registered
Join Date: May 2003
Posts: 132
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Thanks for the info. I'm learning more and more about these rings. Neil at Performance Developments uses a Copper-Beryllium ring which is stronger than the aluminum but has the same expansion rate as the piston and cylinders. I have also talked to people that use a stainless steel ring.
The problem seems to be that there is no common ring size. Each machine shop has their own formula. It looks like my only option is to get the heads o-ringed to match. I'll check with Todd at Protomotive to see if their ring size will match.
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Victor Toce 2000 Boxster S w/ Tequipment exhaust 1993 Spec Miata 87 911 turbo - sold 3.4 RUF pistons and cylinders Euro CIS head |
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03-12-2004, 05:36 AM
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1985 Porsche 930 Fac. Slantnose 3.3l
