2 bbl to 4bbl

[VictorII]

Recurving a dizzy is pretty easy. You simply put in lighter springs and an adjustable vacuum advance and experiment with the transition between mechanical to vacuum advance to optimize your ignition. The standard curve is really slow. You want it to come in a little more quickly and top out at aroud 3,000 RPM. You also want it to run higher at idle. Check out the Crane site. I think they have a pretty good guide. I did it and picked up a little power and stopped the pinging. And if you can't get it right, put the old springs back in.

 

[D.Hearne]

so the vac secondary is when you have a carb that only uses 2 barrels untill needed...so a regular 4 barrel is 4 barrells all the time?

The first part is correct, the second part is not. As far as I know or remember, there are no 4 bbl carbs that open all 4 bbls at the same rate. The mechanical secondary carbs such as Holley's double pumpers, open the primary bbls first, then at a certain point the linkage pulls the secondaries open, til at wide open throttle ( WOT) all 4 bbls are open completely. Now if you have a 2 x 4 Ford setup such as I ran on my old 427 lowriser, you DO run on 4 bbls ( the primary sides of both carbs) til the engine's vacuum pulls the secondaries open. At that time, it's HEY BUBBA, WATCH THIS!!!!!!

 

[ratio411]

If you use an Edelbrock carb, a poster is right, 500 cfm is what you want. That carb is not a vacuum secondary, so it will try to force the secondarys on the engine even if it doesn't need it.
The Holley 600, or even 750 vacuum will not overcarb your engine if adjusted properly.
I would like to comment on a remark about the F4B being a 'knockoff' of the Ford Cobra intake...
No sir!
The Ford intake was a knockoff of the F4B.
Edelbrock made all of Fords specialty intakes during that time period... still do as a matter of fact. That is why you can buy a Ford part numbered Victor Jr today.
Dave

 

[65fastback2+2]

so now im fully confused on carb choice

 

[D.Hearne]

What's confusing about it? Just buy yourself a Holley list # 1850 4 bbl carb.