carb choice for turbo

[Anonymous]

not sure if this site has been covered before or if i saw it before when doing some other searches but its a familiar site...so sorry if its been covered.

http://www.vs57.com/indextech.htm

AFB carburetors can be used with at least 8-9 pounds of boost (some have been used with up to 18 pounds of boost, using solid floats) without the need for an air box, and were indeed sucessfully used in this way by Studebaker on their R2 engines. They are available with a large range of cfm capabilities, and can be found relatively cheaply.

Gary Sypherd reports that if you are using a new or nearly new AFB, you don't need to change anything but the jetting up to 22psi(the point at which the floats collapse) and the accelerator pump seal. He found that the accelerator pump doesn't leak, nor do the throttle shafts, nor from any other "hole". Depending on horsepower, you may need to chage the inlet needle valves as they come stock from Edelbrock at .935" diameter. Edelbrock makes .110's and Carter has .120's

 

[xctasy]

On a street Mopar or 409, the Carter AFB and AVS carbs are one of the best around. The produce better results than Holleys or Qjets, but are not easily adjusted. They are solid zinc alloy, don't suffer fuel leaks like Holleys as the split line is horizontal. The throttle bodies seldom leak. Excellent float bowl. A 625 AFB can sit forlorn for yearsa, and get a new lease on life with just a clean up.

Turboed, they aren't a good choice for our I6's, unless its a Big Block 240/300.

The parts are old, the inventory isn't as full as it is for the Quadrajet. The Rochester Qjet is not a good blow through carb as far as I'm aware, due to the very sensitive nylon bushed baseplate. They have metering rods serviced by Edlebrock now, though.

Holleys suffer massive metering problems at high boost. They cannot be easily tuned to provide lean low boost fuel supply, and then rich high boost metering. The arrangement with the 4-bbl Carters is metering rod tuned, which is much better for varying, (not platic or alloy Qjet style 9800 series)

Best option, on a blow through on a log headed six, are two Carter carbs, covered in a bonet, or two 32/36's. There are ways of making them work okay. There is a plentiful supply of jets, and there is a way of covering them with a complete boost box which allows the stockj fuel pump to be used without a hobs valve or complicated extra work.

My opinion, of course!

 

[Anonymous]

so it would only be for vee-8's then eh looks like I'm gonna end up going the 2 carb route after all then...2 carter YFA's gonna be allright if i get a solid float? or will i have to do some upgrading to keep seepage from the idle mixture screw and throttle body as well? or are u talking about 2 2bbls or are there 1bbls that come with available jets still?

 

[xctasy]

Solid floats are only ever needed when you are running a carb which isn't fully sealed. A couple of YF's like Mustang Geezer (stuck record Stevenson strikes again ) looks like they can be covered by a simple 10 long by 7 inch high by 6 inch wide stainless steel presure box. So long as it is sealed, no problem. Two 32/36's or 5200 Holley Weber out of a 2 liter Pinto would work better.

The rule with turbos is that it must be lean when its off boost, and richen up when on the boost. There is no other option. Twin YF's would over juice the engine most of the time, as they flow very well.

I've never build a gasoline turbo, so I'd look at just a mild Does 10's or 200 drag-stang set up, or Import Killer set-up.

There are many guys doing it, good honest experience will tell.

From the Aussie carb turbos of the late 70's and early 80's, draw throughs were lousy. Blow throughs, such as the Ford Lazer Turbo, were not though of as reliable, but they ran Weber progressive carbs. Freddy Gibson, a very sucessful Turbo Nissan compaigner, found that the Weber carbs were very easy to pressurise. HKS sold many kits, and they worked well, with 50 to 60% boosts in power with stock low compression engins, and only 6 to 9 pounds of boost.

On a six, two of those Ford 2, 2.3 , 2.6 and 2.8 liter progressive carbs would be perfect for every dollar spent, in my opinion.