Venturi sizing, planning for my winter project Options

[jr91472]

ok, so Britt's crazy thread about the mysterious "two-throat webers" got me going on my upcoming winter project: Addition of Dual Carbs.

First to all you FI guys....I know, I know (IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif)

Now to my question: My 1.8L engine (actually 1.7 heads w/ 1.8 p/c) already has a "carb friendly cam" and a progressive weber. Once again..... I know, I know (IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif). Unfortunately I have no specs on the cam other than it was installed to worked with the progressive.

Now I want to install a set of dual carbs. It sounds like most recommendations are of the 40mm variety. My question is about vent sizing. An article on Aircooled.net states that Vent size should be 3-5mm smaller than the Intake valve. According to the manual, the intakes on 1.7L are 39mm, so looks like I need 34-36mm venturi's. Yes / No? (IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif) Seems too simple.

It also troubles me because I have read several 2.0L guys using 32mm vents (with 42mm intakes)(IMG:http://www.914world.com/bbs2/html/emoticons/confused24.gif)

thoughts anyone? Standby for future questions about jet sizes (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

sorry for the long post