Has anyone tried a blow through system on some of the common 2 bbl carbs (BBD)? I have read some on the modifications needed to blow through a Holley, but what about other options.

General direction is a BBD or other 2 bbl on stock 2 bbl intake, not wanting to have to ruin entire budget on 4 bbl intake and Holley carb, if possible.

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1976 Dart Lite /6 3 Speed

It is possible to use the BBD for Blo-Thru.

But one thing about that would be the mechanical power circuit over the vacuum circuit that the HOlley's use (metering rods instead of power valves). You could end up with going into boost at part throttle and needing the power circuit to come in and it would not be able to becuase of being mechanical, to where the Holley being vacuum ( or in this case boost ingauged) would give the extra fuel when the boost comes in.

Many people that just run low boost use the Holley with the power valve in stock config ( not a boost reference power valve) but the power valve still opens when boost comes in. With the BBD the power circuit cant come in untill you give it more throttle.


People that use the Edlebrock (carter type ) carbs get by with it because the metering rods are operated by spring pressure against vacuum, and not mechanical.



IMHO using a Holley 500 two barrel on a super six intake would be the easest cheap setup you should use. The 500 two barrel would need seting up exactly like the Holley four barrel carbs, except you only have to work with one side. Believe it or not boost on a Holley 500 two barrel could reach some pretty impressive horse power number ( atleast 500 to 600hp) and on a slant six it may be able to make just as much as a four barrel under boost(maybe).

The super six intake would be the restriction really with a setup like this. As strange as it may sound the factory one barrel 1920 Holley carb might be a good setup to try. It has a vacuum over spring power valve and a removable metering block that would allow even further modification, and yes it to could make a lot of HP even though its small size (probably around 400hp if done right).


The biggest problem with carbs and boost is controlling the power circuit, and transitioning part throttle operation. The WOT tuning is the easy part.

I believe if going the cheap route, the Holley 500 on a super six, or the one barrel factory Holley 1920 setup would be the two routes worth looking into. A Weber on a super six intake could be another possible choice. The BBD I think would end up in trouble unless something out of the norm was done to make it work, like doing away with the power circuit and making your own, or running richer jets to make up for no power circuit. The richer jets to make up for no power circuit would not be a good street setup though, race only.


To be honest, the price of a good fuel system is going to make the price of a carb that works seem kinda small. And the fuel system is atleast half of what it takes to make a carb work in a blo-thru app. You need more fuel for a 400hp turbo setup, than it takes for a 400hp N/A setup, and its pressure needs to rise with boost and when running a fuel system at higher pressures its harder to keep up the volume.


Still though, one way or the other its doable.



Jess