Dual quadrajets on tunnel ram BBC

[avmechanic]

One of my future projects is a 55' Chevy gasser. I have a 489cu BBC with ported rectangular port heads. It has fairly stout Engle solid roller cam. It will be running fenderwell headers. It is a 4 speed with 4.56:gears. While not very streetable I would like to be able to drive this on the street at times. I have a Offenhouser dual 4 tunnel ram to run. While I have pairs of both 600 and 750 AFB carbs available to use in my Horde of parts I also have some Q-Jets. I like doing things a little different and was thinking it would be cool to mod up two Q-jets to go on the tunnel ram. I was wondering if anyone would talk me out of it or give me some encouragement and info on how I could make it work. What do you think? 

[Cliff Ruggles]

I've set up a few sets of Q-jets for dual quad applications.  First you need to start with two identical cores.  I use and prefer the early style Chevy divorced choke carbs for this as they are side fuel inlet and very compact, plus generous linkage to hook things up on the throttle linkage.

They are built the same as any single Q-jet would be for the engine except no bypass air is needed in most cases at there will be idle air from both carbs.

They work really well in those applications because you can control air to the engine going to full throttle instead of dumping both carbs on the engine like many other makes do........Cliff

[avmechanic]

Do they have to be the same part number or can I just use the same style core? I have a couple early style chevy cores that I could use. I thought the Q-jets would probably work well. The project is a little way off but I think I will work towards making this happen. Thanks for the info Cliff.

[von]

I always wondered how you'd want to set up the linkage for this. Would it be best off idle to open the primaries of one carb first, then bringing in the other at say 1/4 throttle and having both primaries open the same amount at about half throttle; or by just making things simple by opening both carbs the same amount at the same time?

[qjetsrule]

Here's a progressive linkage on a 426 Hemi. The rear primaries do all the work until about 40%. The slotted linkage then picks up the front carb which has a faster opening ratio. Kinda cool.

https://www.wallpaperup.com/872550/1970_Plymouth_Superbird_nascar_mopar_race_racing_muscle_426_hemi.html

[von]

That's the type of linkage I'm thinking would work well.

[Cliff Ruggles]

They don't have to be the same part number but it would be better if they were. 

There are minor differences between almost every part number in how the factory set them up.  So if you use different numbers you will want to check everything and make them mirror images of each other......Cliff