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Registered
Join Date: Sep 2005
Location: Winnipeg, MB Canada
Posts: 221
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How to lower compression on a 3.6
What are the options for lowering compression on a 3.6 964 motor? (to get it down to about 9:1 compression)
Shave pistons? Spacers under cylinders? ?? Kirk
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1989 911 Carrera 4 (964) |
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04-11-2007, 04:05 PM
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Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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Kirk:
Don't use spacers as that adversely effects deck height. Increasing deck height increases the propensity for detonation by leaving more end-gas at the perimeter of the chamber near TDC. Machine the piston domes but you'll not get it to 9:1 without seriously compromising piston strength,..............
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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04-11-2007, 05:05 PM
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Posts: 3,563
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I've heard of many people machining the domes of the 964 pistons down to 8.5:1 for forced induction application without any dramas, even for up to 1.2bar of boost.
I believe Henry of Supertec has done this many times with great success, as does Protomotive. The 964 piston crowns are very thick. You can't do it with 993 pistons though.
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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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04-12-2007, 07:34 PM
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Registered
Join Date: Sep 2005
Location: Winnipeg, MB Canada
Posts: 221
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Thanx guys.
Im trying to figure out all the options for installing a supercharger I picked up. Its quite the learning curve! Kirk
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1989 911 Carrera 4 (964) |
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04-12-2007, 08:40 PM
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