Carburator Question

[Sammuzzu1]

I have a stock '63 Catalina. 1A1 engine with a fac. 2bbl. There is a large standard screw adjustment on the firewall side (back). There are the 2ea. fuel mixture screws on the front. What is the big one on the back for? I cannot recall ever seeing something like this before? Any info would be great.

Thanks,

Sam

 

[melsg5]

I could be wrong but looking at the pictures on this link, your screw is not an adjustment but a plug somebody put in to block a vacuum port.

http://www.ebay.ie/itm/181869736049

 

[Sammuzzu1]

I took a few pics.

 

[melsg5]

OK I found a reference to it. It is an idle bypass screw.

http://6364cadillac.ning.com/profiles/blogs/running-rich-and-how-to-adjust?xg_source=activity

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[Sammuzzu1]

Thank you my good sir! That makes sense then.