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holley 2bbl on a 4.3

A way of determining size for a carb is CFM=cubic inches x RPM x volumetric efficiency divided by 3456. A normal stock engine will be in the neighborhood of 80% volumetric efficiency. A 262 ci v6 at 4800 rpm and 80% VE is 291 CFM. Holley does make a marine 300 cfm in a couple of versions I believe. If memory serves, the base bolt pattern doesn't match. You could compare mounting gaskets for the two different carbs for compatibility.
 
A way of determining size for a carb is CFM=cubic inches x RPM x volumetric efficiency divided by 3456. A normal stock engine will be in the neighborhood of 80% volumetric efficiency. A 262 ci v6 at 4800 rpm and 80% VE is 291 CFM. Holley does make a marine 300 cfm in a couple of versions I believe. If memory serves, the base bolt pattern doesn't match. You could compare mounting gaskets for the two different carbs for compatibility.


Supposedly a V6 will run on a much bigger carb than a V8 based on that calculation, plus they measure 2bbl carbs CFM at a different vacuum level than 4bbl carbs. I think it has to do with engines actually taking gulps of air rather than smooth constant flow.
 
The carburetor is an interesting read and often the subject of misinformation and ensuing conflict. Always remember that a 390 cfm carb in Nascar supports over 750 horsepower. This would seem to shoot a hole in the bigger is better theory. I've made not a small amount of change over the years in the stoplight to stoplight combat on Saturday night from folks that had all kinds of money into a car but had a really bad combination of parts. That and not being able to get their arms around the concept of the first 80 feet of competition being 80% of the outcome in that realm. You might remember some of those folks that put skinny centerlines on the front and cut a hole in the hood for a tunnel ram and a monstrous pair of carburetors on top of a 283 small block in a 55 Chevy and it pretty much pumped raw fuel out of the turbo mufflers that were hanging just ahead of the rear axle. It would have been probably way worse but the stock fuel pump down there on the side of the block couldn't pump any more fuel. Ahh the looks on their faces when I would hand the keys to the girlfriend and explain that if they were able to get in front of her then they could earn a go at me. Then she would shyly get into the drivers seat and point at the accelerator pedal with her right index finger and look coyly up at me and say "This one on the right is for go, right?"
 
Gawd Jimway, I love your replys, but, how fast would the Nascar boys be if they were allowed to run a 750cfm Holley????
 
I'm thinking fast enough to take flight, and not in a good way. That girlfriend eventually became Mrs Jim, by the way. And it gets worse. I have been recently called out by a cantankerous old friend that is getting to the end of the trail, so to speak. After seeing Mrs. Jim in action behind the wheel, he has requested that she drive his old truck against yours truly. We have recently been rebuilding his old Ford truck for him, amping it up quite a bit. She gleefully accepted. I think I may have done too good a job on that old pickup.
 
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