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I have a 73 F100 with a C4 tranny. My vacuum modulator has two hoses coming off of it. Tried to replace with single hose vacuum modulator but it did not fit. Where do the two lines hook up to? I know one hooks up to my carb. But was told to just let the other hang in the breeze. Does this sound right?
Come on guys somebody out there has got to knows where the these lines go. As of right now I have one hooked up to my carb and the other hanging in the breeze. She seems to shift fine. But would like to hook up correct.
I'm new to this site and late replying to this particular message, but my son was given a 1973 F100 (360FE) that we had to pull out of a field. It had been sitting there since 1996. It too has a 2 port modulator, but attached to a C6 transmission. There are two steel lines that run to the area of the modulator. These are separate from those that run to the radiator. I don't exactly recall where the two steel lines originate in the engine compartment, but at least one goes near the carb. The reason I was at this site just now was to see if I could find out which line should be hooked to which port of the modulator. The rabbits must of made off with the rubber hoses that were previously there.
I've been perusing other threads and it looks like I might be able to use a different modulator with one vacuum connection. Haven't had much time to work on the project, but everytime I come back to FTE I get itching to get to wrenching. We're still deciding on whether or not we want to put much into the current engine\transmission, or wait until we can swap in remanufactured units.
Sorry bout the delay. kid,wife,work, and can't remember what month it is some times . Jjust went outside,.... again sorry man. Mine is plugged in to the last one towards the rear of the tranny and the front one I have plugged off. I hope this helps ya out when you do decide on finishing the ride.
Tailgater73_F100
Savannah, GA
Btw the single connection type modulator was not long enough for the bracket to work properly even after bending the bracket the modulator would leak..
No apology necessary. I can identify with the things in life (kids, wife, especially work) that take away from my time playing with trucks. I appreciate the info on how you have it hooked up and the tip about a single connection type. I'll hook it up as you described. Thanks again.
73 was the first year for EGR valves. It was found that when the EGR opened, intake vacuum dropped causing later shifts. Adding the inner vacuum line which comes from the EGR, helped rebalance the shift points. Normally the inner (smaller) vacuum hose can be plugged off and the port on the modulator left open with no ill effects.