In need for my 307 upgrade to 455 big block

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HotDiggy

Not-quite-so-new-guy
Oct 15, 2022
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What up gbody world. I got a 84 Cutty that Im in progress of a few upgrades.

What would be the best carb for my 455 olds big block?
 
What are the plans for your 455? A 800 cfm Qjet is a nice carb.
 
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What are the plans for your 455? A 800 cfm Qjet is a nice carb.
I mean Im pretty open minded right now. I have no experience like that when it comes to the gbody game. I'm just trying to soak up the best advice I can get as of right now brotha. U got a blueprint suggestion as far as what would give me the best results.
 
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I mean Im pretty open minded right now. I have no experience like that when it comes to the gbody game. I'm just trying to soak up the best advice I can get as of right now brotha. U got a blueprint suggestion as far as what would give me the best results.
You came to the right place. Olds307 knows his olds stuff.
 
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Decide what you want for compression and cam. I have a completely rebuilt 800 cfm Qjet set up for a pretty radical cam, I may part with.
 
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If you're going racing at WOT all day- get one of those fuel dumpers like a Holley. They're a "performance" carburetor to work best with your right foot on the floor.

If your goal is to drive it mainly on the street, and you want driveability and street manners while on the street, get the most advanced street design carb known to man- a Quadrajet.
 
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750 qjet on my 455. Ive tried others and for the life of me couldnt get them to work any better. I give up, runs good the way it is.... lol
 
I appreciate it fellas.

If you're going racing at WOT all day- get one of those fuel dumpers like a Holley. They're a "performance" carburetor to work best with your right foot on the floor.

If your goal is to drive it mainly on the street, and you want driveability and street manners while on the street, get the most advanced street design carb known to man- a Quadrajet.
I think Im leaning more to the Quadrajet. This my first ol scoo so, my goal is to keep it on the street for a lil while. I gotta upload sum pics.

I appreciate your advice for sure.
 
I straight stole this from a Motortrend article I remembered reading back in 2020. I hope it helps.

Hutch

Engines are just big air pumps. All they care about is fuel and air, even if all you care about is horsepower. In fact, horsepower is just a math equation based on torque and rpm. In short, an engine is all about air and fuel, which produces torque, which, using math, we can convert to hp so we can brag to our friends.

Like we said, how much hp your engine makes doesn't matter when sizing a carburetor. What matters is this formula:

Cubic Inches x RPM / 3456 = CFM (cubic feet per minute) / Volumetric Efficiency

According to Westech Performance's Steve Brule, our go to guy for all things carburetor related, you can just assume 100 percent VE when doing your calculations, and that will get you in the ballpark. For example:
A 454 big-block that revs up to 5,900 rpm would need:

454x5900/3456=775

So, it would need a 775 cfm carb assuming 100 percent VE
Of course, that high-performance street engine won't have 100 percent VE so:

454x5900/3456=775x.90=698 cfm

(When adding VE to your equation 1=100 percent, 0.9=90-percent, and so on.)

Because the 454 is less efficient, it doesn't need as much cfm, so a 750cfm carb would be fine while a 650 cfm carb would be too small. All of this, and we never once had to know how much horsepower the engine makes.
 
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