What are the advantages of each?

I'm building a street 440, probably holley 750, or 770 street avenger.

Just wondering on mechanical vs. vacuum secondaries...

sjd

Either can be tuned to work well. Really depends on how aggressive of a combo you are building. A mild street engine will probably do best with a vac carb, a strip engine best with a DP, and a hot street/strip build can do well with either one.

If you are going with a 3.23 or smaller gear ( numerically speaking )I'd go with a vacuum secondary carb. They are generally much easier to live with on the street. Easier to tune. Better mileage. Better in cold weather. Most OEM 4 barrel carbs have vacuum controlled secondary's for that reason.

Auto or 4 speed Trans??

Auto. 3.23 rear. I'm starting from a blank slate, but it's a real RS23 GTX, non-matching. I'm gonna do the 440, auto trans, but 4 wheel discs, vinyl top delete, original color GY9...

sjd

I understand that vacuum secondries work best with an auto and mechanicals work best with a stick or very high stall auto.

vacuum seconds it is then.

carb/intake recommendations?

I was thinking Holley Street Avenger 770 with Performer RPM, or Holley Street Dominator...like I said, it's a blank slate, I've basically got a block and a crank, and some 346 heads (which I may or may not use)

sjd

Quote:

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Holley Street Avenger 770 with Performer RPM

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That's what's on the 440 in my 66 Coronet. Works great for me. The only issue is my hood clearance is borderline and the RPM manifold is 1/2" taller than the standard Performer.

I prefer the DP carbs on my street/strip cars. I like having 2 accell pumps and the fact that when I nail it I know all 4 throttle plates are wide open. I do not use a choke on my 63 but even at 30 degrees F I can pump the pedal 3 times and then hit the key and it fires right up. I have to keep pumping it while it starts and keep it running for a few minutes with my foot on the gas holding it at a fast idle but the vac secondary carbs are real hard to start with no choke when it gets below 50 degrees F. I prefer no choke on my street/strip cars as I start it up every week or two in the winter but I dont drive it when it gets below 50 degrees F. I like the hard launch you can get with the DP also when dailed in as it will launch harder then the vac secondary carb. I am not knocking the vac sec carb as they work well in the right application on street cars but I will take the DP anyday. Ron

I like the VS carbs for a mild setup, or for someone who is learning to tune a carb. Once you understand what the secondary spring can do for your application, then understanding how to tune a DP comes allot faster. A DP carb is definately for the performance applications. They have a quicker reaction to WOT than the VS carbs do but if they are not tuned correctly, the DP will be a dog. Both carbs can be tuned to have excellent response at idle to 100% WOT (but a DP takes more tuning effort to do so), but the DP difinately has the advantage at cruise to WOT response if tuned correctly. I think it boils down to how experienced a tuner a person is and what their driving behavior might be for their application.
My only suggestion would be no matter which type of carb you get, definately study the tuning options of each carb before you buy. The VS carbs are nice with the quick change secondary spring setup, and the metering block on the secondary side (versus the metering plate). Electric chokes can be had on either type of carb and the adjustable air bleeds/idle feed restricters are nice and see thru sight glasses on the bowls can be found for both types of carbs. If you choose the DP I have found that the adjustable secondary linkage is a nice tuning aid.

750/770 vacuum and an RPM manifold is my first choice.If you don't have the hood clearance the regular performer intake will work and the older CH4B works well also.
I would recommend the street dominator on a mild motor with 3.23 gears.It will work but will give up a fair amount of low rpm torque to a dual plane.