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Registered
Join Date: Feb 2004
Location: UK
Posts: 2,230
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Cams for SC Motor
We have a standard small port SC motor with Webers and an SSI exhaust which needs a top end re-build.
We are considering opening up the ports to the early SC spec but leaving valve sizes alone and then changing the cams. We also want to leave the CIS pistons in the engine. Would early 911S cams be a suitable profile or would there be valve clearance issues. Thanks for any ideas. |
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10-07-2008, 03:18 AM
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Moderator
Join Date: Dec 2001
Posts: 9,569
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Chris,
It seems to me that you would need to cut valve reliefs in the pistons, which can be done fairly simply.
__________________
'66 911 #304065 Irischgruen ‘96 993 Carrera 2 Polarsilber '81 R65 Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13) Ex-'88 Carrera (Sold 3/29/02) Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04) Ex-'89 944 Turbo S (Sold 8/21/20) |
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10-07-2008, 07:32 AM
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Moderator
Join Date: Dec 2001
Posts: 9,569
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__________________
'66 911 #304065 Irischgruen ‘96 993 Carrera 2 Polarsilber '81 R65 Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13) Ex-'88 Carrera (Sold 3/29/02) Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04) Ex-'89 944 Turbo S (Sold 8/21/20) |
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10-07-2008, 07:33 AM
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Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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Another voice,.......
 IMHO, cutting valve reliefs in CIS pistons for early S cams isn't a good idea. First, they don't make the same power as the proper double valve relief pistons due to changes in swirl (using S cams) and second, the domes get kinda thin at the cut and I am not comfortable with the long-term durability of that practice. If it were me, I would either scale back your cam selection or use the right pistons for this application,....
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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10-07-2008, 10:20 AM
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