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Registered
Join Date: Jun 2005
Location: Hot Houston
Posts: 307
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another weber jetting question
I am in the process of putting my carbs back on the car after a carb rebuild. I am not sure I have proper jetting yet. The car currently has
1974 2.7L S CIS "S" heads Euro RS P&C GE 40 cams 40MM Webers RS curved dist MSD 6AL Bosch WR5DS Tall PMO manifolds carb jetting: 36MM venturi tall AV F3 tubes 155 mains 180 airs 60 idles Some of the references I have recently seen suggest that this setup should have 175 Airs instead of the 180s. Otherwise it matches. My reason for questioning the setup after seeing the 175 reference is I find VERY little effect when I adjust the idle mixture screws. It makes it nearly impossible to tell when the engine starts to miss. I can never be confident I have them adjusted correctly. I haven't been able to drive the car yet. I hope to tomorrow. I just wanted to start with the best starting point before I start chasing my tail. I also have available F24 tubes 65 idles, 45 idles 170 airs 150 mains Your help is always appreciated.
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Rob Richardson 1974 911S Carbed RS Clone engine Turbo flares 2009 Carrera S - Porsche Racing Green, PDK Last edited by rrichar; 11-20-2009 at 05:53 PM.. Reason: further clarification |
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11-20-2009, 05:51 PM
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Registered
Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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Rob,
Your current jetting is VERY close. If the idle mixture screw adjustments do not make any difference, make sure that the idle bypass scews are properly adjusted. You might also try 55 idles, too. I'm assuming that fuel pressure and float levels are absolutely perfect. 
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Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com |
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11-20-2009, 06:43 PM
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Registered
Join Date: Jun 2005
Location: Hot Houston
Posts: 307
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Steve, as always thanks for your help and insights.
I do believe the floats and fuel pressure are spot on. I have learned from you to make extra sure they are set correctly. I spent quite a longtime getting the floats all set the same. I will try to reset the air by passes tomorrow. One of the things I might have done wrong with them is to set all six of them to the same level as the lowest draw. Something I read suggested that you set each side to the lowest denominator on that side then re-balance the sides with the idle stops. Is that a better way?
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Rob Richardson 1974 911S Carbed RS Clone engine Turbo flares 2009 Carrera S - Porsche Racing Green, PDK Last edited by rrichar; 11-20-2009 at 09:45 PM.. |
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11-20-2009, 09:42 PM
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