Hello, I currently have 1974 2.0 and am thinking on purchasing a big bore kit for it. I have a set of Weber dual 40's and distributor set up for carbs that I will be using on the car but do not know the correct main jet size for the carbs . Any help would be much appreciated.

Hello
I have documents from a German engine builder.
Porsche 914
Venturies 30mm
Mixing tube F11
Main Jet 125
Idling jet 55
Regulating nozzle 180 evtl.200
hope to have helped

This might be a good place to start but depending on engine size you might have to do a little experimenting with jet combinations

It's an air correction jet instead of a regulating nozzle here in the States. Buy the weber tech manual by Bob Tomlinson. Read it until you understand how the carb works. I had to read it several times before i wrapped my head around all of it.

You'll need to buy a carb cam too. Otherwise you won't be pleased with the performance.