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Registered
Join Date: Mar 2007
Location: Chattanooga, TN
Posts: 167
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Cam timing. The most allowable advance and retard?
On a ROW 3.0 with the stock Nikasil 8.5:1 pistons and SC cam what is the most degrees the cam timing can be retarded and the most that it can be advanced before the engine starts to experience piston to valve clearance problems?
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1985 Porsche 911 M491 option 55K miles 1985 Alfa Romeo GTV6 CRG Heron Daytona CR125 Shifter Kart Last edited by Noah Holcomb; 06-13-2008 at 08:12 AM.. Reason: the title was too short |
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06-13-2008, 08:10 AM
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Navin Johnson
Join Date: Mar 2002
Location: Wantagh, NY
Posts: 8,774
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You would have to measure the clearance at the extremes, i.e. set the cam timing further advanced, or retarded, then measure piston clearance through an engine cycle.
Ive set cam outside the "spec" but have checked the clearance, and have a dyno to see the results in real time.
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Don't feed the trolls. Don't quote the trolls  http://www.southshoreperformanceny.com '69 911 GT-5 '75 914 GT-3 and others |
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06-13-2008, 11:10 AM
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Registered
Join Date: May 2003
Posts: 3,346
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These cams had a spec of .9mm to 1.6mm depending on the year motor. So you can safely say they will work in that range. I doubt there would be a performace advantage to going outside that range. If you want to go outside that range just measure the clearance during assembly.
-Andy
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72 Carrera RS replica, Spec 911 racer |
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06-13-2008, 06:01 PM
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GAFB
Join Date: Dec 1999
Location: Raleigh, NC, USA
Posts: 7,842
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Was just talking to a well-known builder about this very subject. Said his shop regularly timed stock 3.0 motors to 1.5mm for optimum performance. Maybe he'll weigh in here...
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Several BMWs |
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06-13-2008, 08:19 PM
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