Distributor Vacuum Hoses

I ordered the distributor vacuum hose kit from WCCC that listed it for all 1968-70 289/302/351W cars, however the service manual shows the possibility of just a single hose from the port on the carburetor to the advance unit with no thermal switch in between.
Now that I had a chance to dig into it, I find that my car does not have the thermal switch arrangement and just has a single hose to the advance from the carb port. It DOES have a pipe plug in the top of the water neck where a thermal switch would presumably go but I have no idea if this is how it left the factory or if there was a repair done sometime in the last 53 years.

Can anybody shed some light on what vacuum arrangements went on which cars?

In the 1968 shop manual, there are nice schematics by combination (engine, transmission, smog, and A/C or not) midway through section 9. I don’t own a '69 manual, or I’d help further.

Be aware that previous owners over the years might have swapped dual diaphragm vacuum for single, or, as you suspect, plugged the thermal switch because they decided they knew better than Ford.


That’s part of my confusion, the '69 manual lists both arrangements as suitable for a 302/351w 2V non AC. Not sure if it is a misprint or if I’m missing something else. I’ll double check the diagrams this evening to be sure.

What transmission do you have? That often plays into the issue

It’s an FMX, the vacuum tree on the back of the manifold is still there with all of the connections. A couple ports capped, but I know they used the same tree on different applications.

Had a chance to take a closer look at the diagram in the FSM. The multi hose with thermal switch arrangement is for the AC cars, so mine did originally come with just the single black hose. Guess I could have saved myself the cost of the hose kit from WCCC, oh well.

Depending on how much hot weather driving you do, you may want to retrofit or add the thermal ported vacuum switch.

When the coolant gets near overheating the valve switches the vacuum advance from ported vacuum to manifold vacuum. This increases the engine RPM at idle to improve the cooling. The change is gradual, not a step from one to the other.

My 69 is an AC car with the switch. I noticed the idle was elevated when I didn’t expect it to be and confirmed the engine was running hotter than it should have. Caused me to diagnose the problem sooner than I might have otherwise, and determine the fan clutch was failing before I had a serious problem.