413 dual quad CFM question...

[33 IMP]

The problem with 500 edelbrocks is that crummy primary booster. When Carter did the 500 thing they did it right. They kept the 1 3/16" primary venturi and 1 7/16" throttle bore but down sized the secondary to 1 5/16" venturi and 1 9/16" throttle bore. What did edelbrock do? Those cheap ***'s just made a restrictive primary booster for their 600 carb. That's 2 parts vs 6-7 parts to do it right. The 600 has the same size primary as a 318 2bbl carb. What part of that is too big and needs down sized? Edelbrock may have been the worst thing to happen to a perfectly good design. Quit buying carbs buy a cfm rating!

Maybe that's why they sell ten times as many 600s as 500s?

 

[lewtot184]

Maybe that's why they sell ten times as many 600s as 500s?

The so called 600 has been around long before edelbrock starting making them. At one time is was somewhat the universal hipo 4bbl carb. It was on many 389 Pontiac variations, buicks, the 300hp 327 Chevy carb, 409's, s/s mopars street hemis, etc. Just a basic universal carb until the holley 3310 came out.

 

[62maxx]

I use edelbrock 600's on my 440 with a ch28 and I can assure you they are none too big. They are the same size as street hemi. They have small primaries and are velocity controlled. Forget the cfm hype. 500cfm edelbrocks are garbage.

View attachment 1764629

What kind of throttle linkage are you using and what else for the TRANS kick down? If you have any part numbers handy, I would greatly appreciate it. !

 

[62maxx]

The vacuum operated secondaries won't open if the engine airflow doesn't demand them
If you were gonna run two 600 holley double pumpers.....? A different answer.



You do know it will probably run better with a performer rpm and a 750 vacuum carb, right? (and probably considerably cheaper.)

I ran two 750 competition AFB"s on mine..... but it was on a crossram maxwedge head roller cam motor. An 850 double pumper on a tarantula was just as fast, and easier to tune.

I agree on the $$$$ factor. I am leaning towards the inline 2X4 intake with the repo "football" air cleaners from Vans Auto for the "period correct" engine set up.

 

[62maxx]

It’s because you think the carbs will discourage a crazy amount of fuel but this is not how carbs work. They work on the draw of air rushing past the choke, boosters and on down which picks up the fuel to mix.

This is where “Jetting” the carb comes into play for any carb. If the jet is way too big, even on a 2bbl., you wash the cylinders down with fuel. The reverse is true with to small of a jet n any carb not delivering enough fuel causing havoc.

The engine will draw in what ever amount of air that is needed at what ever rpm it is turning at and as long as the fuel is metered to be enough, not to much, not to little, the engine will be fine.

The real question here is drivability with larger carbs.
Also, part throttle and wide open throttle.
If the carbs are tooooo large, then jetting can be a nightmare and a good smooth running engine without issues is the concern.

There is a lot to unpack behind this. But! A stock 413 can handle twin 600’s. While a smaller set will have improved throttle response, drivability & probably mileage if you can keep the foot out of it. This is why Edelbrock recommends twin 500’s calibrated for this.

I don’t think it’s a bad way to go BUT IF you need to save a few bucks and/or have twin 600’s on hand, use the 600’s.

Thank you for the education!

 

[62maxx]

Just because you put 1200 cfm worth of rated flow on an engine that doesn't mean the engine will use that much.

How much of the cfm rating an engine uses is the sum of a lot of variables. A given engine might only use 800 worth of what's available.

Vacuum and airspeed play a big part of the equation.

For what it's worth I have 800 cfm AVS carbs on my CH-28 and I am not over carbureted.

Tom

Thanks for the valuable info!

 

[62maxx]

If your looking for performance it's not about some rated "cfm" it's about venturi area; that factor that the common culture chooses to ignore. It's about filling the cylinders quickly and efficiently and cfm ratings by themselves can't do that. People also tend to leave out intake manifold efficency. It's more than just carb cfm.

Maybe the most important aspect is what are you going to do with the car? Just cruising around? Street and strip? Strip only?

Mostly STREET with that "oddball" desire to have the inline 4BBL'S as the period correct set up, back in the day. As a fellow mentioned above, a single 750 cfm with an intake would probably run better AND cheaper. I REALLY wanted the "eye candy" A&A or INDY cross ram (non max wedge) intake & carbs but I no longer can afford that anymore. When that stuff was around $2,500.00 for everything, I thought it was "high" back then.....and as we know now, it's tipping 4 grand.

 

[62maxx]

A lot of larger 60s engines ran 2 - 600 cfm carbs - 409, 427 ford, 428 PI Ford, 413/426 max wedges, Street Hemi, 421 Super Duty Pontiacs. The one thing that distinguished most of them was the ability to make power up to 5,500-6,000 rpm. Even the 302 Z28 optional cross Ram used 600 Holleys I think and could use them because of near 7,000 rpm red line. If your engine is going to top out at 5,000 or so, 500 carbs might make sense but I don’t know about their quality.

PLUS..... why are the 500's more expensive than the 600's? I can't figure THAT out.

 

[lewtot184]

What kind of throttle linkage are you using and what else for the TRANS kick down? If you have any part numbers handy, I would greatly appreciate it. !

I have a factory throttle cable and I modified a stock cable bracket for more adjustment. I made spring brackets and a one piece kickdown rod like factory. I use the edelbrock linkage.
Some of these hoops you don't have to jump thru if you use the lokar cable kit.

What kind of throttle linkage are you using and what else for the TRANS kick down? If you have any part numbers handy, I would greatly appreciate it. !

 

[lewtot184]

PLUS..... why are the 500's more expensive than the 600's? I can't figure THAT out.

Yep, and people keep buying the junk. If you have 500's you can simply use 600 boosters in them and recalibrate.

 

[bobs63wagon]

The 413's in 62 I think ran 2-3447's on the crossram intake. They are 600cfm like the 1405's. They used the 3447's in 63 with the 426 wedge on a crossram.

 

[rumblefish360]

Thank you for the education!

Your welcome! Glad to be some help.

Mostly STREET with that "oddball" desire to have the inline 4BBL'S as the period correct set up, back in the day. As a fellow mentioned above, a single 750 cfm with an intake would probably run better AND cheaper. I REALLY wanted the "eye candy" A&A or INDY cross ram (non max wedge) intake & carbs but I no longer can afford that anymore. When that stuff was around $2,500.00 for everything, I thought it was "high" back then.....and as we know now, it's tipping 4 grand.

View attachment 1765491

Exactly! I’m setting up for multiple carb applications currently. I get told and asked the same thing and my response is always the same. I’m doing it because I want to and nothing more, nothing less. I don’t care what you say, I just want to do THIS and that’s that. I don’t care if it’s cheaper, faster or whatever. I’m doing it my way because I Want to do it this way. That’s all.

All small block below.
Edelbrock dual quad w/twin AVS II 650’s.
Modified 6 pack
MP-M1-TR-twin Edelbrock 750’s for now.

 

[Dave6T4]

Thanks! For some reason , I cannot fathom a big block not getting flooded on a total of 1,200 CFM. But, it is what it is.

440 6-Pack was 1350 cfm. from the factory. 350 cfm. primary centre carb, plus 2 500 cfm. secondary outboards. It seemed to work OK. Where the problem comes, is when someone is putting together a 2 X 4 setup using two primary carbs without the air velocity-controlled blades over the secondaries. These make the fuel flow dependant on how much air the engine can pump. I had a factory 1962 Chrysler 300H 2 X 4 inline on a 426 Street Wedge in my 1964 Polara 500 convertible. I think the carbs were around 450 cfm. each, and they both had secondary air valves under the boosters. I ran progressive linkage on them. The carbs for factory dual setup had the linkage attachment points at different heights. This allowed the front secondary carb to open faster, so it would be wide open at the same time as the rear primary carb.

 

[gtxrt]

6-Pack was 1350 cfm. from the factory. 350 cfm. primary centre carb, plus 2 500 cfm. secondary outboards.

Holley 2 barrel carbs are rated different compared to how they rated 4 barrels. even if they were 1350 cfm it was down to like 990 cfm when rated like a 4 barrel. some guys say the end carbs were not even 500 cfm but who knows for sure.

 

[rumblefish360]

6 pack cfm wise is 955 cfm when converted to the 4bbl measurement. Still! Not to dang bad considering it is set up to act like a 4bbl when working right.

The mechanical set up is a little more but I forget what it converts to cfm wise

 

[RemCharger]

6 pack cfm wise is 955 cfm when converted to the 4bbl measurement. Still! Not to dang bad considering it is set up to act like a 4bbl when working right.

The mechanical set up is a little more but I forget what it converts to cfm wise

That's with the 340 or the 440?

As far as the old carter 600s go,, I always thought the Carter performance carbs were good and the Edelbrocks not so much

 

[rumblefish360]

That's with the 340 or the 440?

As far as the old carter 600s go,, I always thought the Carter performance carbs were good and the Edelbrocks not so much

Both