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say you have a 302 v8 ford which has a bore of 4inch and a 3 inch stroke, with normal mild cam and compression in it, that 302 has a ci of 37.50 per cylinder ..and for compasion reason the carb is a 650 cfm, now say you have a motor that is 300 ci, nearly the ci , but is only 6 cylinder aka ford 4.9 liter straight 6 with a bore of 4 inch and stoke of 3.98 which gives you a ci per cylinder of 50 ci, would the same carb work or would it require a bigger carb if the said six cylinder has same compression , rpm etc..
 

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The cylinders my be a different size, but with the V8 the cylinders fire every 90 deg, were the 6 cyl fires every 120 deg. Most likely they would use the same carb, as the v8 would have more overlap between 2 cylinders on the intake stroke for a longer duration then the 6cyl.

Hope, that make sense
 

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Carburetors specifically designed for v6 engines are rated differently. Instead of using the standard 1.5 inch preessure drop used to rate v8 carburetors, they use a 3 inch pressure drop. For the reason stated above.......less (but stronger) intake pulses. Meaning that the v6 will create less "pull" on the carb. This mostly applies to the 2 barrel carbs. Which is why the Holley 500 cfm is essentially the front half of a 750. Conventional math says it should be a 375, but suck harder on it (3 inch pressure drop) and it flows 500 cfm. It's all relevant to the engine, of course. Put your 650 on a prostock and zing it up.......is it flowing 650? No. Probably more like 1200. Something to keep in mind when spec'cing a carb for your 6 cylinder.
 

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Carburetors specifically designed for v6 engines are rated differently. Instead of using the standard 1.5 inch preessure drop used to rate v8 carburetors, they use a 3 inch pressure drop. For the reason stated above.......less (but stronger) intake pulses. Meaning that the v6 will create less "pull" on the carb. This mostly applies to the 2 barrel carbs. Which is why the Holley 500 cfm is essentially the front half of a 750. Conventional math says it should be a 375, but suck harder on it (3 inch pressure drop) and it flows 500 cfm. It's all relevant to the engine, of course. Put your 650 on a prostock and zing it up.......is it flowing 650? No. Probably more like 1200. Something to keep in mind when spec'cing a carb for your 6 cylinder.
its not a v6..its a 306 ci straight 6
 
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