1999 454 carb swap. best street carb, 600? 650? 750? CFM

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Nasty-LSX

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I have this carb now it it sucks really bad. Not even going to rebuild it.
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I'm not asking what carb I need I'm asking whats the best CFM for a stock hydraulic roller 454 with headers and full 2 1/2 in exhaust.
Came out of a 1999 2500 suburban. Vortec fuel injection converted to carb. Its not a race truck just a tow pig or commuter to where ever it goes lol. here is what it looks like in a video. I dont have pics. SQUARE BORE weiand intake.

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carfanatic63

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People might disagree but a good quadrajet is hard to beat.

Flows 750-800 cfm, great street manners, plentiful, etc..

Been running one on my 454 for 10 years (intake, headers, exhaust) and it's been fantastic. Starts below freezing, hot, never bogs, great power and throttle response.

It's got better throttle response than most efi systems on new cars in my opinion.

Negatives, they are old at this point so some used ones are missing parts and/or warped. They are also difficult to set up compared to a holley or edelbrock but once they are dialed in, they are fantastic.
 
Nasty-LSX

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carfanatic63 said:
Negatives, they are old at this point so some used ones are missing parts and/or warped. but once they are dialed in, they are fantastic.
Click to expand...
I agree with everthing you said, but this is why i will not buy a used one. Just going to pic up a Eddy AVS II. :happy160:
 
ali_c20

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The AVS 2 has a great throttle response. I run a 500 cfm on my crate 350 in my K5. I calculated the cfm I need with a carb size calculator. I feared it would be to small but it runs better than ever before. Order a tuning kit with the carb.
 
75gmck25

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The Edelbrock AVS2 seems to be a reliable solution that will probably only need some minor tweaking with springs and rods if you buy the 750 cfm version. A Quadrajet has the potential to be an even better solution, but it’s usually hard to find someone to set it up right.
 
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What are your complaints? Anyway, best to stick with a square bore carb, adapters suck, generally. Bigest problems with slappin a carb on a FI engine is, they tend to run too rich, and re-calibration is necessary, lots of times. I used to be a wiz at Q-Jets, even set them up for racers, back in the day.
Personally, holly's are easiest to change jets and things in.
 
Nasty-LSX

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bucket said:
I'd say it can be a happy engine with anything in the 650-850 range.
Click to expand...
Thanks Bucket. I dont want to over or under carb it, Thats why I ask. Just was not sure what a stock 454
should have.
 
Tonimus

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I've got a QFT SS 850 on my 383. Excellent carb. Was also on a 427 and a 350. Ran great on the 427, just a little big for the 350.
 
JD Miller

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Get a Quadrajet. Its the Best Carb

I have 3 , 800 Q-jets .

My '81 k20 350 factory original is a 800 q-jet

Built Motor has Hi-perf. heads, perf. Cam, headers, edelbrock perf. intake etc. running a 800 Q-jet with rebuild parts from Cliff Ruggles
https://cliffshighperformance.com/

(Typo, 800 cfm not 850)
 
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SquareRoot

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carfanatic63 said:
It's got better throttle response than most efi systems on new cars in my opinion.
Click to expand...

Assuming both are properly tuned it's impossible. A dry flow system (EFI) will have better throttle response than a wet flow system 100% of the time. Law of physics. Just saying.
 
bucket

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SquareRoot said:
Assuming both are properly tuned it's impossible. A dry flow system (EFI) will have better throttle response than a wet flow system 100% of the time. Law of physics. Just saying.
Click to expand...

I'm not arguing, but can you explain this further?
 
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The stock carburetor from gm would of been a 800cfm Quadrajet with electric choke.
 
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The Q-jet carb is only 800 cfms if you open up all 4 barrels if just driving moderately the front two barrels on a Q-jet are 600 cfms. Everyone bad mouths the q-jet but one of the best street carbs ever made no power valves to blow out and cause a fire. If you want a little extra power as a big block would want at higher rpms the two larger barrels are there to do the job.
 
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