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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 
				__________________ 1989 911 Carrera 4 (964) | ||
|  04-11-2007, 04:05 PM | 
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| Registered 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,.............. 
				__________________ Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com | ||
|  04-11-2007, 05:05 PM | 
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| Registered Join Date: Mar 2002 
					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. 
				__________________ 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   | ||
|  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 
				__________________ 1989 911 Carrera 4 (964) | ||
|  04-12-2007, 08:40 PM | 
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