Quote Originally Posted by Giovanni89 View Post
Base timing should be set with the vacuum advance disconnected. Remove the hose and plug it so there is no vacuum leak. Then set your timing to 7BTDC and reconnect the vacuum.
When running manifold vacuum to the distributor you will get full vacuum advance at idle. I don't know what the pull from the vacuum mechanism is, but i suspect when you retard your timing all the way to get 17BTDC, your actual base timing is somewhere around 5ATDC.
There are two brass ports on the side of the Weber, one ported and one manifold. All you have to do is take the plug out of the ported side, swap the hose, and put the plug in the manifold side. I wanted to be a believer in running full manifold vacuum, but I found that the biggest drawback is a large loss in engine braking performance. I tow with my truck with some frequency and the service brakes aren't that big!
Thats the problem is that if I try and set it without the advance hooked up I can't get close to the 7 BTDC. I can only get 17 BTDC or 2 ATDC