I recently did a little work on my engine, replaced water pump, thermostat, and thermostat housing, etc. When I went to put everything back together, I noticed the ported vaccum switch? coming out of the thermostat housing (see attached picture #1). This piece has three nipples on it which hoses connect to, one hose looks like it goes into the exhaust manifold (see attached picture #2), and the other hose goes into my vaccum diaphragm (see attached picture #3). The probelm is, I only have these two hoses to connect to the three nipples, and I can't remember how it was connected before. Can anyone shed some light on how (what order) and which hoses I need to hook up to this piece. I can explain more or add more pics if that helps. Thanks in advance, Brad
I think that the two hoses coming from your distributor vacuum advance go to the top and bottom fittings, and the middle goes to a manifold vacuum source. I do not know which goes to the top or bottom. From you picture it looks like you have the dual advance vacuum on your original distributor. Unless you have emissions requirements in your state and you are not allowed to alter your system.....you might want to look into a single vacuum advance for your distributor and connecting it to ported vacuum off of your carburetor. Ported vacuum is a source above the venturi plates. From what I have learned and remember the dual advance is switched when the thermal switch (the 3 way tree) gets above a certain temperature. The thermal vacuum tree and the dual advance units can and do go bad over time from engine heat and age.
hoses Look carefully at that switch on the thermo housing, it should tell you which one goes where. one to manifold, one to dizzy, one to carb ported as noted above. The switch should be marked .... should be
Egr Valve(or egr VSV) should be the 3rd line. I'm fairly certain. But, I can't tell you what order they go in. When you run with the egr open you need more ignition timing but you should only open the egr valve when the motor is warmed up. Thus, the need for the VSV(vacuum switching valve). In Texas the law says you got to have a EGR valve but, does not state that it has to work. Down here I would connect the egr to the vsv and not plug anything else to the vsv. Then plug the other lines. The egr is mainly a way to reduce NOx emissions and can cause(or help cause) carbon build up in the intake and valves. It does have one minor benefit, It actually cools(no really!) the intake charge during part throttle and allows a leaner mixture and more ignition advance while cruising. Some motors (not all) can see a gas mileage increase of 0.5 to 1 mpg with an egr. That mainly applies to high compression engines.
Uhhh....yeah I hate to jack your thread, but I've been asking this same question for quite some time now.... My 302 has the same tree on the water nozzle but none of it is hooked up. There is also a plugged 3/8 vac line on the front of the carb plate, and another tree on the rear of the manifold, with one big 3/8 nipple and a few 3/16 nipples, also with no apparent reason to live. Anybody have a diagram or photos of their properly connected vacuum harness? And please stop telling us we only need two lines! P.S. I have a single line vacuum advance.
I am sure that there are lots of variations for vacuum routing. Anyone trying to do it correctly should check the specific year shop manuals. I looked at a 1970 shop manual and did not really find what I was looking for. There were a couple of examples, one showed the distributor vacuum modulator, one did not. Both examples were for V-8's Pretty sure that there was not an EGR in 1970.
my 200 has the same 3 connection tree, it hasnt had anything pluged into it for as long as i can remember. i dont think it has caused any problems so i left it alone
My vacuum advance runs off of that tee on my 250. Car seems to run ok. I took the car to big O today for an alignment, and the guy called me cracking up. He said the strut bushings need to be replaced because they are missing but he would probably have to order them for a 72 maverick. He said he would put the car inside and take good care of it until the parts arrive. I guess I forgot to check those when I rebuilt the front end. It was steering like crap and jumping whever it wanted.
302 lines Actually on a dual vacum distributor two of the lines on the tee go into it. One goes into the advance side and one go's in to help the retard side. (note this is pre egr motor 1972) if your distributor only has one line going into it then the third T should be capped.:16suspect
Unless your state requires it, just get rid of all that crap. You only need one line going from the intake to the vacuum advance, and one line going from the intake to the modulator on the transmission.
I know this thread is a little old, but I've been searching through info on the web trying to determine some things about the vacuum system on my car as well. What I found strange is my engine has a dual vacuum advance distributor even though they were used on 75-79 cars and mine is a 71. I also had a PVS valve (three way valve in the thermostat housing) that wasn't connected to anything. I still don't know why I have a dual vacuum advance distributor, but I did find out that the PVS valve was used on some cars with AC. The top line goes to the carb vacuum source, the bottom line goes to the manifold vacuum source and the middle line goes to the distributor vacuum advance. The reason for this is to increase the idle speed when the engine runs too hot while you're runnin your AC in the blazing summer months. When the valve gets too hot it switches from the low vacuum of the carb to the higher vacuum of the intake manifold which increases the timing advance, increasing rpms/fan speed/coolant flow thus lowering the engine temperature. The back side of the daul vacuum distributor is connected directly to the intake manifold. This is used to retard the engine timing under periods of closed throttle, (idle/decceleration) to lower engine emissions.
