08-14-2009, 01:14 PM
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CC Member
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Join Date: Aug 2007
Cobra Make, Engine: 31XX Car
Posts: 374
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Choke size
Quote:
Originally Posted by priobe
Dcmgt,
Peak power was made 5800 rpm ( If memory is correct).
It is a 427 Ci
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Ok, for peak power at 5800, the choke/displ parameter would be about 32. Rearranging the equation and plugging in yields 2*(32*427/25.128)^1/2 = 46.6mm choke diameter if you don't want power to be limited by choke size.
There is a rule of thumb of how much greater the carb bore size should be than the choke and I recall it's around 20% by memory (can't remember whether that was based on diameter or area). So a 46.6mm choke ratio'd up by 1.2 is about 55.9mm carb bore. Now imagine if you wanted peak power more in the 6500+rpm range, you can see how the ideal choke size would approach 50mm and the bore size to go along with that is 58mm........we just went through a similar exercise to what Shelby American/Ken Miles went through to determine carb size when they were developing the big block Cobra race cars.
For you're planned usage, it would probably be ideal to have 48mm IDA carbs bored out to 52mm (a common procedure done by shops I believe like Berg) and run something like 45mm chokes.
Last edited by DMXF; 08-14-2009 at 01:17 PM..
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