carburetor size on a 350

I need help.
I know stock Chevy 350s are happy with 650 CFM carburetors. That being said I have a 750 Edelbrock 1411 on my non bored over 350 9.93:1 compression that is far from stock.

It has an Edelbrock dual-plane intake, A lopey 510/520 lift cam (2200-5800 RPM) and aftermarket vortec heads that I have ported and Polished myself.

Whenever I tell people I have a 750 CFM on a 350 they freak out saying my carburetor is too big but to me it doesn't feel like it's too big. When I stomp on the gas it does not bog it just goes, when I read my spark plugs either after daily driving it for a while or driving it hard the spark plugs look clean with light amount of soot around the ring at the end of the threads (in other words they look fine to me) and the vehicle idles fine. If this will tell you anything I have a vacuum reading between 15 and 16 inHg. I have not changed Jets metering rods or Springs.

When I tell people (including shop owners) that the engine runs fine. they say oh well it's still too big you're probably losing to tuneability or losing power at higher rpms.

So what I'm asking is is my carburetor too big, if not what defense can I use to make these people stop freaking out and what are the signs that a carburetor is too big?


1985 chevy c10 262 v6 swapped to around 400hp 350 vortec heads
Stage 3 700r4

Tell them the standard Quadrajet flows that much or more and stop talking to those people?

If you're happy and the engine isn't then it'll let you know.

I'd tell them to shut up! The guys on Engine Power run a 950 regularly on their dyno, even on small blocks.

2 CFM per cubic inch is a rough rule of thumb I was told many, many years ago.

A mild 350 I used to have ran much better with a 750 double pumper than it did with a 650.

Craig 85 said:

I'd tell them to shut up! The guys on Engine Power run a 950 regularly on their dyno, even on small blocks.

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And Frieburger put two 750’s on a tunnel ram in the Crusher Camaro with a small block and ran in the 10’s.

I have been messing with my new vortec (350 horse),engine with a 600cfm quick fuel carb. on it and it runs great but I thought it should have more. I just put a 650 double pumper, (brawler) carb. on it for fun and it feels like I added 40lbs. torque and pulls harder on the top end.

Your 750 eddie carb. is good to go imo.

Tell them eat a bag of dick's

The shop that swapped my 305 to 454 told me my edelbrock 1407 wasn't big enough for the 454. It didn't run bad just seemed to be lacking power for a big block. They told me I needed a 850cfm carb. Lol

I'd just bought a quadrajet for the 305 before I found the 454. Switched them out with the help of an adapter plate for the intake. Figured if the quadrajet didn't help then I'd get a different one.

The quadrajet was a big improvement over the edelbrock. Much better throttle response and ran much better overall. So it's quadrajet for me.

82sbshortbed said:

The shop that swapped my 305 to 454 told me my edelbrock 1407 wasn't big enough for the 454. It didn't run bad just seemed to be lacking power for a big block. They told me I needed a 850cfm carb. Lol

I'd just bought a quadrajet for the 305 before I found the 454. Switched them out with the help of an adapter plate for the intake. Figured if the quadrajet didn't help then I'd get a different one.

The quadrajet was a big improvement over the edelbrock. Much better throttle response and ran much better overall. So it's quadrajet for me.

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What cfm Quadrajet did you have?

82sbshortbed said:

The shop that swapped my 305 to 454 told me my edelbrock 1407 wasn't big enough for the 454. It didn't run bad just seemed to be lacking power for a big block. They told me I needed a 850cfm carb. Lol

I'd just bought a quadrajet for the 305 before I found the 454. Switched them out with the help of an adapter plate for the intake. Figured if the quadrajet didn't help then I'd get a different one.

The quadrajet was a big improvement over the edelbrock. Much better throttle response and ran much better overall. So it's quadrajet for me.

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Carter and then Weber were what the edelbrock carbs were.Had edelbrock,never ran as good as my qjets tho.But then I never cared much for Holley either.But that is sacrilege in some circles. Lol

chevyninja350 said:

What cfm Quadrajet did you have?

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Most are 750 to 800. Guessing Mines a 750. Been told since the secondaries are vacuum controlled the carb will adjust to the amount of vacuum it's pulling. Not an expert on this just watched some video and read some articles on them. Here's a good one on the cfm on quadrajet carbs.

https://www.hemmings.com/stories/article/rochester-quadrajet-carburetors

Gm put the quadrajet on for a reason. Still get great throttle response while giving you the best gas mileage.

I know this is beating a dead horse, but unless you are mainly doing full throttle blasts down a drag strip, a quadrajet that’s properly tuned is extremely hard to beat.

I ran one Edelbrock carb for a while on a daily driver and didn’t care for it. Swapped in a quad and was much happier.

I still run a Holley on my play truck that doesn’t get street driven much. Fuel efficiency and driving manners aren’t a concern. I want full throttle performance and a Holley is easiest to tune, for me, in that scenario.

Sounds like this problem. “My significant other wants to jump my bones twice a day, you guys think that is too much”?

Waylon said:

I know this is beating a dead horse, but unless you are mainly doing full throttle blasts down a drag strip, a quadrajet that’s properly tuned is extremely hard to beat.

I ran one Edelbrock carb for a while on a daily driver and didn’t care for it. Swapped in a quad and was much happier.

I still run a Holley on my play truck that doesn’t get street driven much. Fuel efficiency and driving manners aren’t a concern. I want full throttle performance and a Holley is easiest to tune, for me, in that scenario.

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When you think about it, the Q-jet is far and above a more advanced carburetor than the Edelbrock. Really the only thing the Edelbrock has going for it is simplicity. It's easy to work on, tune and rebuild. The Q-jet I think gets a bad rap because it's complex and some people will mess them up during a rebuild.

As to the CFM thing, if 750 is working for you run it and forget able what others say.

I like simplicity. My bone stock 350 Goodwrench crate engine runs just fine with a 600 cfm 1405/Performer dual plane Edelbrocks.