Carb size/ brand

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dartlove

dartlove

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So I am looking for a Little Help from the racers. I am in the search for a carburetor for my 496 . Has 14:1 compression. Indy 4500 flange intake. Trick flow max wedge heads. 2 1/4" exhaust primary's. Question is 1050cfm enough or should I get a 1250 and jet down. Strictly bracket race car.
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At WOT, If the carb is really to big for the motor it will run lean. The engine doesn’t move enough air through the carb to create enough signal through the venturi. At WOT velocity of the air is what pulls the fuel. There is no manifold vacuum. To big not enough velocity.
 
furrystump said:
At WOT, If the carb is really to big for the motor it will run lean. The engine doesn’t move enough air through the carb to create enough signal through the venturi. At WOT velocity of the air is what pulls the fuel. There is no manifold vacuum. To big not enough velocity.
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So how do I figure this out? Is it also based on venturi size. Doing this one on my own don't really have the help that I used to for making selections
 
With a bracket car I would err on the small size. It will give you better throttle response and be more consistent. I have no experience with the “big” carbs, but if you don’t get an answer there’s a guy thats supposed to be pretty good at setting up those carbs on moparts. Thumperdart.
 
I would contact some of the specialty carb builders. A 496 will do quite well with a good sized dominator. Exact CFM I don't know but it may not make that much difference on a bracket racer. Main thing is consistency and the specialty carb builders can do that for you.
 
dartlove said:
Great thank you
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If you are on moparts look up Dominic. He runs Thumpr carbs. You can probably find him on Facebook. If you can't find him, PM me and I'll give you his phone number.


Let him pick the carb and let him build it. The initial cost will be a bit higher, but the carb will work. And he answers his phone to help with tune ups. Don't buy an off the shelf carb.

Just my guess but I think if you call Dom he will tell you you need something along the lines of 1400 CFM.

Personally, I can't see any smaller myself but I'd let Dom help you as I've been wrong before. Many times.
 
Dom has really helped a lot of folks out. I’ll be consulting him this fall as I’m finally taking the 4150 off my W8 mill.
 
yellow rose said:
If you are on moparts look up Dominic. He runs Thumpr carbs. You can probably find him on Facebook. If you can't find him, PM me and I'll give you his phone number.


Let him pick the carb and let him build it. The initial cost will be a bit higher, but the carb will work. And he answers his phone to help with tune ups. Don't buy an off the shelf carb.

Just my guess but I think if you call Dom he will tell you you need something along the lines of 1400 CFM.

Personally, I can't see any smaller myself but I'd let Dom help you as I've been wrong before. Many times.
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^^^^^^^^^^^^^^^^
I go w/ this post. I have a 1200 cfm throttle body on a 505, just changed to a more fuel inj. friendly cam, drove it yesterday , it was about as responsive as a hot sbc, pleasantly surprised !
 
Here's a slightly different way to look at it. The main air bleeds can be adjusted to get the AFR flat through redline so don't worry about that. A larger carb will have less restriction at WOT than a smaller carb. If fuel distribution and vaporization in the cylinders is really good, less restriction will make more power. But a little restriction (talking 1/2 - 1"Hg more) can help distribution and atomization which produce more power on setups that need that.
I agree with the suggestion to work with Dom or Mark W. It will save you time and money in the long run.
 
Been a while since I've looked into carb selection. But carbs were picked by intended application. A 4500 might be meant for an IR manifold. Or two on a tunnel ram with a manual trans. My 1150 was intended for use as a single carb,modified class,auto trans. Variables could be,2 or 3 circuits, accelerator pump timing, style of booster, throttle linkage. 1 to 1, soft,progressive. Power valves and so on. The closer you fit the app the less mods needed.
 
And please,forget everything you know about jetting up or down to this or that. The motor will tell you what it wants. You just gotta listen. With an A/F meter,reading plugs or what traps the fastest.
 
This AED carb was built to my application. They asked quite a few questions as far as cam specs ,compression, heads used, Gearing ,converter ,and I'm probably missing a couple other things.
 
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