I have a question on this switch. I am putting an engine out of a 1974 Olds 98 into my 1970 Cutlass Supreme. I am going to put a new ported vacuum switch in, and it looks like they are different for the 2 years. Which one should I use?

 

Personally, I'd just plug the port and bypass it. My second choice would be to go with a 1970 version of the valve.

 

The 1974 cars don't use Transmission Controlled Spark because they have EGR to control NOx emissions. The 1974 ported vacuum switch is simply used to switch vacuum advance from ported to manifold if the engine starts to overheat.

 

There was one on it and I just wanted to replace it so I was just curious.