Just curious as to what the little vacuum switch screwed into the manifold does, with the three ports. I checked Year One and it looks like it's called a Thermostatic Vaccum Switch. I ran my finger over each of the ports, at idle and there doesn't seem to be any vacuum from any of them. There were not lines connected to any of them either, and the ram air setup is not installed right now, would that connect to those? Also, does anyone know where I can get a good diagram that shows where each vacuum line goes? I have and assembly manual that I got form EBay, but it isn't easy to read. I noticed that the car hesitates and bogs for a second or two and then runs fine. When I picked up the car, the vacuum advance was connected to the port on the right side of the Q-Jet, and it wouldn't advance the timing, but when I switched it to the port on the left front (not the port for the secondaries), it seemed to run better, but I haven't had a chance to run it yet. I sprayed carb cleaner around the base of the carb and the open vacuum ports and nothing seems to change with the idle. I'm so confused, the lines are all spliced and tees are put in, I thing I need to just get a diagram and start from scratch. ou: Thanks in advance for the help!! Scott
Without knowing what year and motor you have, I'll take a stab at this. That switch prevents the EGR or vacuum advance from getting vacuum when the engine is cold. Unless you are worried about concourse points, just disconnect the EGR and bypass the dist. advance so it goes directly from the carb to your distributor. You'll be surprised at how much better it will run this way.:bglasses:
Oops, I was going to put the year/motor and got sidetracked by a nice street rod driving by the house, I had to run out and check it out. It's a '70 GS Stage 1, all stock. Scott
That car shouldn't have an EGR valve, those started showing up around '73.......but I would guess the thermal vacuum switch is connected to your timing advance circuit. I'll let someone else chime in here, b/c I am not certain of the specifics here and I don't have a '70 service manual to look at.:bglasses:
The thermal vacuum switch sends full manifold vacuum to the distributor vacuum advance if the car gets too hot. It has two inputs -- one for ported vacuum and one for manifild vacuum. The bottom of the switch senses coolant temperature. The output goes to the distributor vacuum advance. The cars were set up from the factory so that the distributor got ported vacuum -- that means no vacuum at idle - to the distributor. But in case the car got too hot, the switch sends full manifold vacuum to the distributor. This makes it run cooler. The full manifold vacuum advances the timing at idle, and a cooler running engine. But it's not as emissions friendly.
