What Size Holley Carb. Mechacical or Vacuum Secondaries

[Mike Z]

What Size Holley Carb. Mechanical or Vacuum Secondaries

Selling The Dual Quad Setup on My 68 Charger. Was way too much Gas. Has a 400.
Has slight cam and was bored .30 over. With Hooker Super Comp Headers. Has 3:55 Sure Grip and 2200 or 2400 stall convertor. Going to go with a Edelbrock Performer RPM intake.
What size CFM Holley Carb Would be the best in a Double Pump?
Manual or Vacuum Secondaries?
Thanks In Advance.
Mike Z.

 

[Meep-Meep]

Sounds like a street car that spends most of the time from idle to 3500 RPM. If that's so I'd go with a vac secondary carb that is specifically calibrated for street driving and not racing, and a bit on the small side like 670 CFM. I am more concerned with keeping the primaries on the small side rather than looking at total CFM. I'd personally go with an AFB. Perf RPM should do well but not mandatory.

 

[gtxtc]

How big is the motor? I would run atleast an 850 double pump on a 440.

 

[Mike Z]

WOW I did not put that in there. It's a 400. Now edited.
Mike Z.

 

[coloradodave]

Good advice from Beep Beep. First off, all Holley double pumpers are mechanical secondaries. They were designed as race carburetors with NO consideration to gas mileage. Vacuum secondaries are the way to go if you're going to use a Holley. Just look at the factories where they used them on all the high performance applications that I can remember. OR, use an Edelbrock Performance carb around 650 cfm. Great mileage, vacuum secondaries and really easy to tune.
Good luck with your choice.

 

[67 B-body]

Didn't 68 chargers come factory with the 383 option? I think I would just stick with that and go on.... I know it's a 400,,, but that's not going to matter much in this application.
I realy enjoy going to the old parts manuals and looking up replacement parts (as they were) for these ol' heeps that we all love to death!!!! I kinda figure that Mother Mopar did the calculations for us regarding street applications.
You'll probably find that Meeps,, (or is it Beeps...LOL) recomendations are spot on.
It sucks loosing the "Cool" factor of duel 4's though...

 

[Mike Z]

Thanks Guys For The Advice.
I did'nt buy a carb yet.
On the Chassis dyno way too much of a shot of fuel.
She runs ok with it and it looks Super Cool But with 2 Carter Competition 625's too much gas.
Loads up pretty bad when at lower speeds through the Towns.
I Bought it like this and tried to make it work.
I have the Dual Quad set up sold when I pull it off so I'm figuring out what to get.

 

[Al K]

MikeZ;On my 413,I switched from a Holley 750 vac. carb to a Holley 670 Avenger Vac. unit. With a slightly better cam(214/224 [email protected],.442"/.465" lift),E-brock Performer 440 intake,low-stall converter and 3.55 gears,I've got a very driveable package. It seems to like the 670 better. I'm running #70 primary jets,#74 secondaries;nothing else was changed from standard specs,and the plugs are medium tan.

 

[coloradodave]

Mike,
I am confused which seems to happen more and more these days lol. Are you saying that your dual quad set-up USES too much gas (read- can't pass a gas station) or it's running too rich? If it's the 2nd option, that can be TUNED out. You can put a single 600 cfm holley 4 barrel on your car and if it's jetted way wrong it will foul plugs and use lots of gas. The Carter AFBs are very easy to lean through the use of replacement jets and metering rods / springs. You can buy a strip kits for your particular carbs that contains parts to get the tune-up just right or take it to a performance shop that does this kind of work. If you like the dual quads, save your money and get them tuned correctly. If you have a local speedshop I'll bet they can recommend somebody to square it away.
Good luck, whichever way you go.