C-4 Vacuum Modulator question

[keithb]

Ok, I am finally getting this truck together. My C-4 has two vacuum hoses that go to the modulator valve. My 73 pickup C-6 only has one. That one was easy, but where do the two lines go on the bronco? I figure one goes to manifold vacuum while the other must go to the carb for ported vacuum. But I don't know which is which or if this is even correct. Anyone know this stuff? I have the rear most port on the valve going to manifold vacuum. Where do I run the other one and is that the correct order?

Thanks

 

[BwoncoHowie]

Plug the small line and don't use it. A 72 bronco does not have the EGR system to support the dual modulator. The large line is the only one needed for best results. Perhaps later you can upgrade to a single diaphram modulater. ~bh

 

[keithb]

Oh. That makes sense. I did buy a new modulator and it only had one port. I took it back thinking it was wrong because it wouldn't work with the retainer clip. I'll just plug it. It's actually in a 75 bronco that I am building for a friend. But it doesn't have egr either.

Thanks for the help.

 

[72_EB]

I had a dual port modulator on my '73 California 302/C4 that had an EGR before I ditched that too. My retainer clip broke so I need to make a new one out of flat stock anyway. I went with the single port yellow stripe modulator. Been running that one for at least 4 years.
Good luck.