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Old 06-19-2008, 02:30 PM
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SuperHart SuperHart is offline
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Join Date: Mar 2001
Location: Cinnaminson, NJ
Cobra Make, Engine: Cobra Fibercraft Bodies 427 S/C, 351W disguised as a 427.
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Not to get into a discussion about mechanical versus vacuum secondaries, but Shelby used vacuum secondary carbs for a good reason, the secondaries open as engine demand increases rather than being either closed or wide open with those extra pump shots of fuel to cover the flat spots which is a waste on the street. Of course, I talk about only Holley carbs. Sorry Edelbrock and Carter AFB lovers, those carbs just don't cut it on a Shelby Cobra. Using a pair of 600 cfm carbs on your 427 is still overkill. A 427 at 7000 RPM assuming 100% efficiency will only need 875 cfm of venturi area. I had a friend who used a pair of Holley #8007 390 cfm carbs on his 427, fiddled with the jets a little and loves them to death. Then again, he drives 100% on the street and never pushes the motor to the breaking point. In addition, when mounted on the intake and covered with the S&H air cleaners, they look identical to the 600s. One last point, if you choose to run dual Holleys, ALWAYS use the dual quad secondary diaphragm cover kit to equalize the secondary diaphragms.
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