Which carb should I use??????????

[duster360]

I have asked this question before, but now I have other carb options here on the shelf. I need some opinions on what size carb to run on my combo. This is just a weekend cruiser with an occasional beating to clean it out. I have these 3 carbs on the shelf to pick from. Should I go holley 650 or 700 double pumper or 670 vacuum carb and why? I promise I won't ask again for this combo, so don't beat me up too bad for asking for a second opinion. Plus some of my combo changed a little.

67 Dart
340 ci
Edelbrock 60779 heads, no porting
Edelbrock Air Gap intake
Hughes engines roller rockers
Comp cams XE275 HL
10:1 compression
4 speed
3.55 gears

Comp cam specs:
Hydraulic flat tappet
Basic Operating RPM Range:
2,000-6,000
Duration at 050 inch Lift:
231 int./237 exh.
Advertised Duration:
275 int./287 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:
0.525 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:
0.525 in.
Lobe Separation (degrees):
110
Grind Number:
CRS XE275HL-10

 

[goldduster318]

650 double pumper, but only if it's not one that's set up to be pig rich. They are more responsive than Vacuum Secondaries. Otherwise if you don't care so much about that go with the 670 vacuum.

 

[Bad Sport]

I thought vacuum secondary carbs were better suited for auto cars. Or is it they work better for an auto as opposed to a DP?

 

[d55dave]

650 double pump. It is sized appropriately for the 340. For performance, with a 4 speed you can't beat a double pump because it has mechanical secondaries. When you're shift gears you let your foot off the gas. With a vacuum sec it takes the secondaries a moment to get the vacuum signal and reopen when you lay the pedal back down. With the mechanical secondaries they are open as soon as you lay back into it. It will be more responsive.

 

[duster360]

The only thing that concerns me about the 650DP is I am worried it might lean out at high rpm, I won't turn it more than 6200 rpm though. Or would it be fine.

 

[Bad Sport]

Here Jaimie, play around with this:

http://www.carburetion.com/calc.asp


Of course it's not gospel, but it will give you an idea.

 

[duster360]

Using that calculator I came up with 579 cfm.

 

[Fisher]

A 650 DP on that engine would be nice. It is a 4 spd car too. Jet it properly, run a power valve on the primary side and a plug on the secondary side and you should be fine. A 650 will give you a **** ton of throttle response down low too, with 355 gears i think the 650 would be right.

 

[rumblefish360]

650DP, no go play!!!!

 

[duster360]

650 it is then. Just bought a kit for it today.