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Old 10-26-2013, 08:54 AM   #1
CF Senior Member
Member Since: Jul 2009
Location: Englewood FL
Default 1961 Dual Carb Idle Mixture Adjustment

My '61 has dual WCFB carbs - 270 HP. I'm working on adjusting the idle mixture starting with the screws backed out 1 turn. I've shortened a 1/4" barb plug for the next few days until the Paragon 755 comes.

It is a challenge to adjust the back carb given the very limited space. Even my carb adjustment tool can't make the bend to get into it so I'm using a 1/4" open end wrench. Anyone got a recommendation for a tool for this?

But more importantly where do most carbs end up for turns out? My engine has the best vacuum when they are about 1/2 turn out. Is that consistent with other dual four engines? And what is the typical vacuum gauge reading? I also seem to have a slight range where about 1/8 of a turn doesn't make any difference. Should I be on the in, out or middle of this?

And anyone know of a good video for this? I can't find a good one on YouTube or with web searching.
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Old 10-26-2013, 09:56 AM   #2
Frankie the Fink
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Member Since: Aug 2007
Location: Winter Garden Florida

My vacuum at idle on my 270hp dual quad car is a rock steady 18". I have the Duntov 097 cam.

Idle mixture screws are from 1/2 to 3/4 turn out on all four. I am running clone carbs but they are set up just like real deal 270 carbs. Worry less about the number of turns and more about highest vacuum/best idle. When you reach that I always lean the carb idle screws out about 1/16-1/4 turn on each screw. The idle will roughen up then settle down but it prevents over rich idling. I use this tool for the back carbs (I tried a 1/4" box end wrench and those springy flex shaft tools and they suck) - it works but is EXpensive:

You use it withOUT a bit in it and then its a regular 1/4" hex driver. Its well made and includes a ratcheting mechanism and dial indicator so you know EXactly how many turns (or partial turns) you are moving a carb screw...

The incredibly short Philip's head bit for this tool is also perfect for tightening the screw on the back of the turn signal housing using a 1/4" box end wrench to hold it. So - you do get a 'two-for-one' use out of it.

BTW - I run the screws in until the engine acts badly and screw outwards to the highest vacuum point and no farther - so any dead spot is not a factor. I doubt you'll find a YouTube video on these carbs as you are now in an elite cadre of classic car owners with Carter WCFB dual quads - there aren't all that many of us. But the procedure is no different than any other carb.

Last edited by Frankie the Fink; 10-26-2013 at 10:17 AM.
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Old 10-26-2013, 09:56 AM
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