I have a Weber 4 barrel carb (don't know the exact model though) and I there's two screws in the front. Which way do I turn them to make it leaner? I'm pretty sure I'm running rich now because there is a more prominent fuel smell when I drive. Thanks for any help.
For adjusting your air/fuel mixture,
connect a vacuum gauge to a good vacuum source, A good starting piont is 1 1/2 turn out from bottom(on a holley), turn each one in or out until highest vacuum reading is achieved.if you dont have access to a vacuum gauge,listen for highest idle.
then adjust your main idle.
Before you do any of this I should mention your timing should be set where you want it.
Unfortunately...the screws only effect idle richness. Has nothing to do with the motor when you are driving. Even if it smells rich, does not mean that's what it is. I'm afraid that if you smell gas, there is probably another problem.
( I believe grego, you always set main idle first. )
THe Webber should be the same as an Edelbrock. I just bought and installed and Edelbrock performer 600 cfm for my car. It has the webber name all over it, I beleive the Edelbrock bought all the castings from webber a number of years back.
Anyway, I don't know if you have any trusted mechanics near you or not. I just took mine to my guy yesterday. I was running rich, backfiring and all. HE adjusted it in less than 5 minutes and didn't charge a dime. All he used was a screwdriver and his ear.
I've got a 4 BBL Edelbrock carb which I'm pretty sure is the same as your Webber. I have had poeple try and adjust mixtures by ear, but the best method I have found so far is to have it put on the dyno tune and set up correctly. Its not a large expense given the accuracy and the performance it provides. My car has never run better - starts first go every time, idles smoothly and pulls hard all the way through the rev range.