On my 72 Cutlass sbo there is a thing on top of the engine,near the front and to the left (facing the front of the engine) of the temp sender that has a switch sitting on top of a small tower with three vacuum ports. None of the vacuum ports have hoses but when you have the ignition on and touch the connector to the switch, there is a definate "click". I just bought this car and am having some of the wiring and vacuum hoses replaced, but don't know what to do with this thing. It screws into a water jacket and that adds to the confusion. I plan on taking it out an plugging the hole in the water jacket. If I do, am I going to mess up anything of use ?

 

It is an emission control thermal vacuum switch for the distributor. Transmission controlled spark (TSC) switch. It changes disty vacuum from ported or none (depending on tranny gear) or manifold vac if car starts to overheat.
It can be easily bypassed and removed if you do not want it. Just run the disty to either poerted or manifold vacuum (mine is on manifold).
If you do not want it, do not chunk it - I will buy it from you as mine has tested bad. There may be a day I restore its functionality.

 

That is your thermostatic ported vacuum switch. If it has been bypassed and the engine runs properly you can remove it, plug the hole, and stow the electrical connector.

 

Thanks for the replies. I'll plug the hole and go with full vacuum to the distributor. I've never had a small block anything that doesn't run better with full vacuum. Those guys who insist on ported either don't understand the differences or think they have to go by the book. Oh well that's another subject.
Thanks again for the replies.

 

I understand the differences between ported/manifold distributor advance and also understand the difference between *****-out performance and street driveability. You use the vacuum source that best suits what the damn car is being used for. You also use it to tune your vacuum advance curve if it's being used. If you lock the distributor at full mechanical advance, you need neither manifold nor ported vacuum. So don't come on here telling us we don't understand the difference or think we have to go by the book.

That being said, your "electro-vacuum thing" is an emissions device that controls distributor advance depending on 1) coolant temperature and 2) transmission gear. It will not allow vacuum advance to the distributor until the car is in 3rd-4th gear (stick) or high (automatic). That's what the electric part of it does. The temperature function switches between ported and manifold depending on coolant temperature and is used to advance timing at idle if coolant temp goes above about 235 degrees.

If it works and is in good cosmetic shape, it's highly sought after by restorers and those guys who think they have to go by the book. Otherwise toss it in the trash.

Kinda telling that those of us who have the books know what the thing is.

 

wtf??

 

NOT the dreaded Ported / Non-Ported Debate again?!?



- Eric

 

Not the ported/non ported debate from me. I shouldn't have brought it up. I know, after a great deal of testing, what has worked best for my small block engines over the past 30 years , so to each his own.