This statement, makes me think you do not understand how a vac sec carb works. It does not depend on intake manifold vacumm. The vacumm is developed by the airflow thru the carb. The higher the airflow thru the venturi, the greater vacumm is developed, and applied to the secondary diaphram. I know how it works, but I think I am going to confuse you trying to explain it. Perhaps someone can do a better job of that.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Martin, you seem to have already convinced yourself that you want a 600DP.

My main questions would be how much gear are you going to run in the rear, and is it a stick or auto? If you'll have lees than a 3.91 and a good loose converter for an auto, I'd stay away from a DP carb.

Anyway, get a 390 VS Holley and be done. The amount of real world performance you'll give up is negligible.

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Official Cookie and Mater Tormentor.

The engines that run 600 dp carbs to good effect carry short gears; Lower ratio than 4.10's. They run lots of stall. 3800-4200 would be a good range. That would be behind a slant, so a much higher stall number behind a V8. A 3000 rpm stall converter behind a V8 may stall in the 2400-2500 rpm range behind a slant as an example.

Here's the deal with the Edelbrock. Once it's set up, you won't have to mess with it. None of the gasket surfaces are beneath the fuel level. There is very little to go wrong in there. They will work at varying temperatures and altitudes with less issue. You won't have to mess with the jetting.

Basically, an OEM 500 Edelbrock performer will work out of the box. The amount of tweaking is minimal. If anything, the metering rod springs might have to be changed out and you may need to toy with the pump shot.
I run faster with my Carter 500 AFB by 2/10ths than with a Carter 600 AFB. The Edelbrock is a newer bit of engineering on the same design as the Carter.
I run about the same with the 600 Holley Vac Secondary as with the Carter 600. The big difference is; I don't have to fuss with the Carter at all. The Holley needed played with every time I changed 500 feet of altitude, or the temperature changed 20°F. With the Carter/Edelbrock, that doesn't phase it.
My gears are 3.50's. My stall is 2500.
My cam gives me great signal, so I run the heaviest metering rod springs. You may have to run something else. Fopar runs a bunch more cam, and runs a Carter 600. He's a tad quicker than I am, and daily drives his cars. Once it's set, leave it alone.

2¢

CJ

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Part of Tyrde-Browne Racing

You are rigth, I was wrong on VS operation!!! Thanks for your imput, I will look for additional info on how it works NOW on the web.
I was, now I'm NOT!!!
My car will have 3,73 gear, 245-60-14 tyres, manual trans 1st gear 2,84.
But I have four different manual trans to choose from. I'll open a different post on this, maybe you can also help me to configure my car for drag.
Ceej: Thanks also for your imput.

So, no DP carb. Got it!!!


Now about the 390 I think I can do better with a 600 Vac. Sec. since the primaries are sized just the same as our OEM Holley 2300. And with the 600VC carbs I have more options to choose from.

About Edelbrock carbs I should learn the difference between the Performer 500 and the Thunder AVS 500 carb to see wich one is more suitable. Now i know that I should seriuslly consider the Edys carbs, so I need to start reading on it's operation and calibration

Thanks again for your imput. Here in ARgentina the 4bbl carbs are not common at all, we are used to play with Holley 2300 or Dino Webers, but not 4bbl, thats why I have so many questions about them!

So it will be either a 600VS or a Edy 500. Thanks!

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Martin Zappettini
1974 Dodge Polara RT 318cu.
1965 Valiant III Coronado Slant Six 6-Pack (soon!!)

The two offerings from Edelbrock are the Performer and the Thunder AVS series.
The difference is how the air valve works. There are butterfiles in the secondary that work like a mechanical, but there is an air valve above them that is controlled by air demand.

The performer uses a weighted air valve. The Thunder uses a spring air valve.
To adjust the air valve in the performer, the weight has to be adjusted. This is accomplished by drilling holes to lighten the weight, or by adding weight to increase it. Less weight allows the secondary to come in sooner, more makes it come in later. If holes are drilled, they should be sized so they can be threaded to put the weight back if it causes a bog.

In most cases, the weight won't need to be fooled with.

The AVS allows you to increase or decrease the spring pressure that keeps the air valve shut. It's a much more useable tuning feature, since you won't have to take the carburetor apart or epoxy weight to the air valve. It also begs to be played with, so can take you in a big circle that generally ends up back where it was set by the factory.

When I started out with Edelbrock carbs, I knew I could make it better! I changed primary jets and metering rods searching for the perfect tune. And ended up with the stock jets and rods in the thing!

Hope that answers the question you had about the AVS and Performer carbs. They are very tuneable, but generally, you won't have to.

CJ

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Part of Tyrde-Browne Racing

Once again CJ thanks on your imput!!! Are you shure you don't work for Edelbrock?!!! because you almost got me into this carbs!!! LOL
I spent the last 3 hours learning about them on the web, just because of you!!

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Martin Zappettini
1974 Dodge Polara RT 318cu.
1965 Valiant III Coronado Slant Six 6-Pack (soon!!)

I'm evil.

CJ

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Part of Tyrde-Browne Racing

Ahem, Ceej who talked you into using Edelbrock!


Richard

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Part of Tyrde-Browne Racing

Whatchoo talkin' 'bout? I got a Carter!

CJ

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Part of Tyrde-Browne Racing

Ceej, you know they are the same just different name

Richard

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Part of Tyrde-Browne Racing