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Old 03-02-2004, 09:37 PM
Bruce Robles Bruce Robles is offline
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Join Date: Oct 2003
Location: Surprise, AZ
Cobra Make, Engine: 2004 Kirkham 427 Roadster. New BBM Sideoiler Block, 484 cu. in. built by Valley Head & Racing Engines, Northridge CA. installed 3/20/2016
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Bruce Edwards,
You are spot on about the vacuum secondaries verses mechanical. All Cobras, & Shelby Mustangs built both for street and road course's came with vacuum secondaries.
We ran a GT 350R with the 715cfm carb with vac. secondaries. Same as on my 66 street car. We ran a test with a 750 double pumper on the race car and all it did was drink more fuel. The engine can only use what it can use, and that's it.
We could light up the rear wheels with vacuun carb idling with the clutch all the way out, mash down on the gas and sit there in the smoke. Couldn't do it with the double pumper though, it would just try to drive away like it was in to high a gear, slowly.
On the clock there was no noticable difference in lap times between the 2 carbs just fuel consumption, the double pumper was thirsty, but it didn't give any real benefit.
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