You've got a dual diaphram dist. Which hose is attached to the carb and which one is hanging? The hose that doesn't go to the carb should be attached to the manifold at a fitting a few inches behind the carb. if everything is stock. <br>The timing should initialy be set to 6~8 deg btdc with both vac lines disconnected and all vacuum ports plugged. This is a good time to check for vacuum leaks with some gummout or WD-40, or something like that.<br>Of the two lines from the dist, the on furthest from the dist cap (closest to the radiator) is the vacuum advance and attaches to the base of the carb. When you hook this one up, the timing should jump up to about 12 deg btdc. <br>The other line, that attaches closer to the cap, is vacuum Retard. It goes to the fitting on the manifold. It's an emissions thing and only functions while decelerating.. It will not affect performance or MPG whether it's hooked up or not, Sometimes it can cut down back-fireing when decelerating but that's the only diff you would ever notice. I would hook it up proper 'cause nothing says "Amature" as loud as things hanging lose, or cut off and plugged off under the hood. The only reason to plug it off is if the diaphram in the dist is leaking. The advance diaphram is just as likely to leak also.<br>A remanufactured dist with all new advanvce, 'tard, and new points adjusted and tested to OEM specs costs about $30. Alot of parts stores have vacuum hand pumps on hand to test things like this.