600 cfm vs 500 cfm

[Chiclassics]

So i have heard from shops, offroad guys and some locals 600 CFM (Edelbrock 1405/1406) is actually okay for stock 302. But when I look up its CFM its around 450+..So what do experts here recommend 500CFM (Edelbrock 1404/1403) or 600CFM (Edelbrock 1405/1406)? What are pros / cons.

My current 1406 gives me a feeling of sluggish response at start/low speeds.

 

[DirtDonk]

Either one should be able to work, and either one should be able to be tuned properly for your engine.
My personal feeling is that the 500 is more appropriate, but that perhaps the 600 could still be tuned more precisely than it sounds like it is, for a stock engine.
From jet sizes, needle designs, accelerator pump settings, and all of the above stuff.

I ran both a Carter AFB 625 and an AFB 500, and liked the 500 better overall.

 

[Madgyver]

Qjet is the way to go. edelbrocks stumbles on speed bumps
my opinion
small primaries, big secondaries for WOT

 

[serial car restorer]

One of my prior projects was a '64 Chevy C10. It came to me with a stock, low compression 305 from an early '80s pickup, and was fitted with a 600CFM 1405 on a Performer manifold. Obviously not exactly the same as a Ford 302, but same basics. The 1405 worked, but I was never totally happy with it. Like you, response at low RPM seemed soft to me. I would have preferred the smaller 500CFM carb. Or maybe I should have reverted to a 2BBL instead. I know I'm pleased with the rebuilt stock 2100 on the 289 in my Bronco.

Another thing I learned when playing with the Chevy was that the manual choke Edelbrocks are set up a bit fatter (for hotter cams) than the auto choke carbs. For a stock 302 I'd start with the auto-choke carbs.

 

[m_m70]

I have had the best performance with the 500cfm 1404/1403 when I was running Edelbrocks.

 

[.94 OR]

I ran a Holley 600 vacuum secondary for years. I never felt like I had the air volume required to fully open the secondaries. I think a 500 would have been a lot better at all things.
I now run a FiTech 400Hp version. I don't run full tilt in it enough to know if I need more air or not, but likely not.

 

[bronco italiano]

I have edelbrock 600 off road carb or Holley 470 truck avenger off road carb for sale. Bothe had less than 5k miles on them before being rebuilt

 

[ared77]

This is not me, but rather something I saw about 4100's in a Vintage Mustang Forum, for what it's worth -


"I just read an article in the Mustang and Fords that stated that the 1.12 carb that was made for K-code 289s only flowed 480cfm. They said that Ford engineers worked hard to design an intake system that matched the flow capacity of the K-code heads. The article justifies the intentionally-low flow capacity by saying " Keeping the inlet velocity up meant outstanding throttle response, and this helped the K-289 wind up quickly..."
The 1.08s flowed even less, something like 430 cfm, IIRC.
The article's flow information is consistent with what I've read over the years."

 

[nrramse]

I had a 600 CFM Holley for a long time (or 650, I don't remember), then switched to a 500 CFM Edelbrock. The 500 has a better low rpm response and is great for stop and go driving in town. It doesn't like getting jiggled around on steep bouncy roads though, even with offroad float valves and fuel pressure regulator. If I were in the market for another carburetor, I'd look at the Holley Truck Avenger or Quadra Jet

 

[BroncoJimbo]

I ran a 600 CFM Holley on my 302 then 351W for years. I replaced it with a 470 TA and it has been flawless. I don't feel the need for bigger carb but then I'm just tractoring around anyway.

 

[Chiclassics]

Thanks for all comments. @serial car restorer good point on manual choke have fatter flow, didnt know this i thought 1405 and 1406 are same. By examining more I realized what I have is a 1405 and the mustang shop I got it from installed a electric choke on it. I thought it was a 1406 and its not.

1405 .100(prim) .95(sec) . Prim metering rod 70x 47
1406 .098(prim) .95(sec). Prim metering rod 75x 47

So it looks like at throttle my primary is giving out 30 (100-70) instead of 23(98-75) which definitely is richer

I would get a 1403/1404 then. Thanks for Holley suggestion guys, I have more comfort in fixing up Edlebrocks so lets see if this works before i start leaning into Holleys.

Does anyone have a good compare of Edelbrocks vs Holleys? is that too sensitive of a topic

 

[DirtDonk]

Shouldn’t be too sensitive for most of us. But I don’t remember a specific list of pros and cons, or even deeper specifics, between the two brands.
Might be because there’s so many models between them!
Plenty of users prefer one over the other, and sometimes it just boils down to what you’re more comfortable with.
But in other cases, there are legitimate pros and cons to each one.
Just depends on which ones are more important to you I guess.

There was an episode of Engine Masters that, if I remember correctly, compared an Edelbrock to a Summit Racing (based on the old Ford 4100 model), and one Holley variant.
All they were testing for was overall power, but at least it gave you some insight as to possible good and bad aspects.
For ultimate fine-tuning, most carburetor experts probably prefer one Holley model or another, over everything else.
But that doesn’t mean you can’t get a good tune out of other types.

 

[nvrstuk]

Chiclassics..."Does anyone have a good compare of Edelbrocks vs Holleys? is that too sensitive of a topic"

Q-jet has much better throttle response than either the Edelbrock or Holley. I've run 'em all, built them all and the air velocity of the Qjet off idle can't be beat because of the "tiny" primaries. Smaller venturi's increase the speed of the air and it's very noticeable off idle. It's about as close to a variable venturi carb as possible. Work great. Does NOT matter that they can flow 750 cfm (they also have an 800cfm one). I have built these and run them on 4 cyl marine engines (yes, they work great on the little 4 bangers), 6 cyl engines, small V-8's, large big block V-8's. Tune them and they can't be beat for on/off road (that's why the Avenger was built). and for on rode driveability for sipping gas when you are trying to squeeze mpg out of your cruise.

 

[Chiclassics]

Just got my used Edelbrock 500 cfm (1404), did some cleaning fully opening it up. Put it on my Bronco and voila , I am getting much better throttle response and happy for what I wanted out of it. Thanks to ebay seller sateabjr . He seems to have good summit racing parts from clearance racks.