factory 2X4 vs homemade set up - flow?

So, using the known vacuum signal level in the dual quads, I should be able to figure out what springs should be used in the secondary actuators to attain full open secondary butterflies. At this point, could I assume the vacuum signal level in the dual quads will be half of what a single carburetor sees? If so, I would just need springs that are half the rate of OEM?

 

Assuming vac source is the venturi signal...I don't think it would drop to half, and if it did it might well be unworkably small. I think it would be more a matter of timing, that venturis would get into the range where they are efficient/consistent later than with one carb, which would be probably OK. I THINK, no actual measurements at my disposal, that venturi signal is pretty consistent over a wide range when sizes are reasonable for engine. You don't want the secondaries opening if primaries are below working range anyway...
If source is manifold vac, ported or otherwise, problems largely reverse...normal vac at idle, vac drops dead quicker as more area than stock opens up. Venturi and manifold depressions run opposite at extremes, probably both high at efficient mid level cruise. Venturi signal is pretty weak, the big problem with making the Loadamatic work at full throttle...and another reason it's a good thing you aren't using that.
And remember, these are really small carbs by modern standards, the reason everyone needed two or a forest of Strombergs on 300-inch plus engines until a few years after 1956 when Carter and Holley started seriously addressing bigger displacement needs.

 

Yes, at a specific throttle blade angle there will be less vacuum, but it just means the throttle position for cruising will be different.

Not necessarily.
An engine that draws say 19" of vacuum at idle will still draw 19" of vacuum at 2000 rpm.

Only by complete coincidence.

 

Waayyy too many bits-o-folklore here. I really try to avoid he said-she said discussions.
However: math isn't going to take you very far in predicting what's happening in a manifold. The pressure drop from a valve opening occurs much faster throughout the plenum volume than mixture flows from an individual barrel.

 

Do any of you guys know anything about restricting down a couple of 1406 Edelbrock carbs for a 2x4 tunnelram? There is a guy who makes air restrictors for the 600s to make them either 500cfm or 400cfm. I've never done it before but I see the principle behind it. I have a fresh 350 sbc with a rough cam, hei, 2500stall, 700r4, 3.36 gears and 9:1 comp. I have 2 1406 carbs but it's overkill in my opinion and thought restrictors might be an option. Any thoughts?

 

By the way they are the restrictors that go on the boost venturies.

 

There is another thread discussing this. Guys have been able to run carbs progressive on tunnel rams and others say you can't. If I were going to run this set up on the street I'd want the carbs small and not progressive.
If you want to sit at a light and stab the throttle wide open you need to not flood the engine with air. Might be hard to do. Remember tunnel rams were made for drag racing and nothing else.

 

Thanks Jimmy, I've looked at other threads but can't seem to find what I need. Do you happen to remember what it was?
Thanks

 

Sorry, don't remember the title.