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Dual Weber L20B


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I think whomever told you that was thinking of deleting the booster. Personally, I'd rather have power brakes than dual carbs, since dual side drafts don't do much without other internal engine mods. A simple downdraft DGV is more than adequate. If you want more than adequate, get ready to spend a couple thousand bucks to bring things up to snuff.


Back to the booster - there are two different size boosters that came on 620's, one smaller than the other, but both of them are still an issue with dual carbs. It is possible to move the booster back the the firewall by deleting the pedestal it bolts to, but this requires moving the clutch pedal/master assembly over towards the A-pillar. Metal fabrication and welding are required.


The intake manifold you would want to use for the dual side draft setup (on a 620) is hard to find too (made by Mikuni). If you can find one, it is quite a lot shorter than others on the market.

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A single sidedraft is supremely underwhelming, but then so are duals on a stock engine. You will see them when you open the hood. You'll hear them when you romp on the pedal, but you won't feel them at all unless you also go for a cam, a good cylinder head, a recurved distributor, good exhaust, etc.


I like Hainz' idea of using the dual Mikunis on a SU manifold.


The four bike carbs are cool too.

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I only have access to Weber’s. I’ve never even heard of Mikunis and we are new to this. My son just liked the way the the Weber’s looked. I was told the Weber’s would fit if we applied shorter horns, but I don’t know for sure. Very confused, so maybe I’ll just tell my son to go with the regular carb. 

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The PHH series Mikuni/Solex carbs are similar to Weber DCOE side drafts, but many people feel they are better, and I agree. But, they are hard to find as they stopped producing them about 25 years ago.


The Mikunis Hainz linked to are a motorcycle carb, and not in any way similar to a Weber DCOE or PHH Mikuni, but are very tempting to try, since they are inexpensive, modern, compact and easy to get.


The "regular carb" you mention, if you're referring to the stock carb, can be ditched in favor of a downdraft Weber DGV, DGEV, DGAS, etc. Those are all very reliable, easy to tune, easy to work on and easy to get. I don't know how old your son is, but if he's young, he probably likes flashy things. So I understand his desire for dual side drafts, but they take a huge learning curve to set up properly and tune/maintain.

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I have bike carbs but similar to the SUs in operation. They don't have an accelerator pump or power valve or a choke flap. They are very different from a usual carburetor. I had to learn how to drive them as they have no bog or stutter off the line or hesitation when floored at any speed. 1,200 RPMs in 4th and floor it and the car pulls away (slowly at first) but without pause and just keeps on increasing it's pull. Hard to do that with a carburetor without stepping into it little by little until it gets going. The slide or SU type (also known as a constant velocity) does this for you and only opens up as needed to keep the venturi vacuum constant. Carburetors are the opposite with low venturi vacuum at low RPMs. 

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The SU’s sound really cool! We are still worried about how any dual carbs are going to fit with the power brake booster. My sons king cab is a deluxe and comes with power disc brakes and he really likes that. We will probably go with the down draft for now. Thanks for all your help. 


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Strictly a '76 1/2 through '77 emblem which coincides with the introduction of the King Cab. All KCs were called deluxe cabs, but there's wiggle room for everything. Maybe they were swapped along with the grill.

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