I am in the process of switching to a carbed setup on my 355. It will consist of the following:

-Comp cam (230/236 dur @ .050, .510/.520 lift, 110 lobe sep.)
-AFR 195cc heads with 64cc chambers
-Edelbrock Performer RPM Air Gap intake manifold
-Probably a 700 CFM Holley carb
-700R4 trans with a 9.5" 2600 RPM stall converter and either a 3.42 or a 3.73 rear gear

I was told by some people to go with vacuum secondaries in order to avoid bog at lower RPMs. I was told by others to go with mechanical secondaries because I will go faster and I should be able to tune the carb so that the lower RPM power is where it should be. So I figured I'd ask the carb guys. My car will be driven on the street quite often, but I don't really care about driveability as long as I turn out good numbers at the track. Any opinions?

Also, I will probably be buying a used carb due to lack of funds. A friend of mine knows Holley carbs like the back of his hand, so I'm guessing I should buy a rebuild kit. Is there a jetting kit or anything I should buy in order to properly tune the carb? Any help would be greatly appreciated. Thanks in advance.

 

If the secondaries aren't opened, both carbs will act exactly the same - although it is possible for the vacuum secondaries to open without being at full throttle.

The bog occurs when there isn't enough air flow to provide adequate vacuum boost to pull fuel through the secondary main metering path. This can happen with either VS or DP, but is easier to "tune out" of a VS carb (make the secondaries open slower/later).

The way Holley puts it is to use VS on heavy cars with engines built for torque, auto tranny and street gears; and DP on light cars with engines built for top-end power, manual tranny and strip gearing.

The key for using a DP on your car is the torque converter - it has to stall high enough for the engine to be in the cam power band immediately, or you'll bog. FWIW, I know a bunch of racers with strip-only or strip-primary automatic cars, and they all use DP's.

For tuning, get the Holley jet assortment from Summit or Jegs. Two of every jet size from 66-99, or something like that. About $40 (cheap).

 

With that motor you'll want a 750 double pumper.

 

I can get an awesome deal on a 700 CFM double pumper ($250 w/elec. choke, brand new). Should I go for this, or do I really need a 750 instead. Thanks.

 

You'll give up probably 10hp, maybe a lil less, but it won't blow your motor up or anything.