Re: Weber Carb Questions - Saab Sonett Bulletin Board -

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Re: Weber Carb Questions
Posted by Chris Hartman [Email] (more from Chris Hartman) on Mon, 1 May 2017 15:49:55

In Reply to: Re: Weber Carb Questions, Greg Lemon [Profile/Gallery] , Sun, 30 Apr 2017 19:07:48
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For a stock V4, the 40DCNF is a bit much. However, they can be jetted down like any carb, and most of them tend to have fairly smaller 32 or 34mm venturis. The DCNF as mentioned, is also synchronous, opening both barrels at the same time. So you really need to dial in the idle mixture. Also, their choke mechanism is "opposite" the more standard weber carbs. The DCNF range actually have a fuel enrichment circuit. The 32/36 carbs instead use a choke plate that blocks air. The end result is the same, a much richer fuel/air mixture. They just do it differently.

I actually had a pair of 42DCNFs on a 1,290cc Fiat motor, and it ran great on the street. It did have a hotter cam, head work etc., but it never felt overcarb'd.

My current Sonett (Jack Ashcraft's Fast Freddy" is a hot rod 1,700cc motor with big valve/port heads, higher compression, F66 cam, big exhaust, light flywheel, needle bearing rocker arms, and it still runs a 32/36DGV5A carb. We've run it in normal non-synchronous mode, added a kit to make both barrels dump at the same time, and I've run the car with a bigger Weber 38DGAS. I feel these carbs are more than adequate for that very well-built motor, so a 40DCNF is likely overkill for your stocker.

And I know people suggested calling Jack Lawrence. Just be cautious with his big solex setup. It is very much intended for road racing applications, and would be a a pig for street driving on a stockish V4, imo.

Hope this helps.

posted by 73.12.214...

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