Okay i was checking out the vaccum advance today. This one has a dual diaphram advance mechanism. The retard side was done plugged which i read is pretty common. Now on to the advance side. Pulled the line off and it held vaccum. Okay short piece of line of the advance then there is a round thing that looks like a small fuel filter. The way it is hooked up now, no vaccum will pass through to operate the advance. If you blow through from the other side, air will pas through, turn it the right way you can not suck or blow through it. I thought okay maybe its backwards? nope it is lableled to carb to advance. I have searched and can find no mention of this thing any where.. so my question is, Do i need this thing?? It looks like the advance aint working.. so any body know what it is called? And if it is needed?? Later!! chris
You have a dual diaphram vacuum advance distributor. The device you are asking about is a spark delay valve. The carb normally has two special ports. One port feeds the valve. The other port feeds a temp controlled gate valve then to the EGR valve. The side port off the dist. goes to full intake manifold vacuum. You need to hook the full system up as designed for the engine, model and the specific car. Otherwise I would replace the dist with a single diaphram design and check if the carb has a port to 'properly' feed vacuum to the replacement dist. The centrifigal internal weights and springs plus the vacuum advance should be calibrated for reasonable action or you could see some pinginig if the advance is to much, or poor power if not enough, so it takes someone who knows a bit about checking out the operation to get it at least close. These original vacuum systems are a pain. Good luck with it.
You do not have to replace the whole dizzy. All you have to do is get a single advance and replace the dual. All it takes is 2 screws and a E clip and it is done. If you want to use the dual all you have to do is use the rear port on the dizzy, I have found that plugging the retard port hampers operation of the advance side. I just leave it open so it can move air in and out. Take the valve out of the equasion and put a straight vacum hose to ported vacum on the carb and you should be fine if you do not want to change to the one port advance pod.
My 72 has the same system. No EGR or anything. Mine won't run right unless hooked properly. The front side of the diaphram uses the carb advance port. That's vacuum above the throttle blades. The little plastic deal you have is a vacuum damper and must be in place. It won't seem right when you manually try to suck/blow through it. It doesn't work that way. The colored side goes to the carb IIRC. The other side of the distributor diaphram (rear port) goes to manifold vacuum, or carb vacuum below the level of the throttle blades. If I plug mine, or mix match any way/shape/form, the timing is screwed up. I left mine stock with the 2 lines running. I intend to swap to a Pertronix and install a single adjustable can, but until then, I don't mind 2 vac lines. Dave
