Ray, I'll double-check when I git home, but I think that may be the "delay" switch for the vac. It delays vac. to the dist. in 3rd & 4th gear on 4 speeds. There will also be a "delay" relay on the firewall, by the brake booster, that powers the switch, along with the switch on the trans...

Thanks Joel.. I will check the firewall also... do you think if it's not working, that would cause hesitation due to no vacuum advance on acceleration... ? 2 cruzn2006-12-20 18:03:34

If it is the TCS switch, there will be no vac. to the dist except in 3rd and 4th gear. Have someone sit in the car, with it running, and put the shifter in 3rd. Then see if there is vac. at the dist. Then check it in 4th also. Remember, if the delay system is functioning properly, there will be about a 20 second delay after shifting before the switch opens, so give it a least that much time to see if it works.
On mine, with the engine running, I can just put the shifter in 3rd or 4th, and the rpms will go up about 200rpms, but the '74s did not have the "delay" function.
The temp switch in the pass. side head also works with this system. It allows full vac. to the dist. until the engine reaches operating temp, so the test with the shifter will not work if the engine is cold. With the engine cold, you should have vac. at the dist.
I can post a full description of the way the system is designed to work tommorrow...it's nap-time for me now...ZZZZZZZZ
This system does not allow for any vac. advance in 1st or 2nd gears, except when the engine is cold, so if you are having a hesitation at take-off, or in 2nd, then you may need to advance the timing a bit to start with. Or, there may be other issues, such as carb jetting/mixture, point dwell, etc.

OK... when do you sleep man ?? 2 cruzn2006-12-19 17:52:54

Otay, here's a little schoolin on the TCS systems...
All manual trans cars in '73-'74 had the Transmission Controlled Spark. It produced retarded spark in the lower gears for better emissions. There is(should be) full vaccuum at the dist on colds starts(below 82F engine temp), and overheat(over 232F). This is accomplished with the temp sensor in the head.
The dist. should have full vac. in 4th gear in both years, and 3rd gear on some '73s.
If the engine is cold(below 82F), when you start it, the idle should be around 1,100-1,500 rpm, and slowly reduce to normal idle as the engine warms up.(This is without setting the choke) This is one way to tell if the system is functioning.
Once the engine is at operating temp,(around 160F-180F), if you move the shifter into 4th gear, the idle should rise to 1,100-1,500 rpm. All small blocks had a time delay in '73, giving about a 10-30 second delay before the switch opens for the vac. In '74, the time delay was removed, but some of the earlier cars still had it.
Not all big-blocks had it in either year.(the delay)

The solenoid switch for the big blocks in '73 was directly behind the carb, with the vac coming from the base of the carb to the sol., and then from the sol. to the dist. In '74, the only change was the vac. came from the intake fitting, not the carb.
The solenoid for the small blocks is mounted on the pass. side front of the intake, just behind the AIR pump. The vac. on these came from the carb to the sol., and then to the dist.

Hope this info helps some. Before testing to see if the system is working, make sure your idle speed is correct, according to the sticker on the cowl, by the brake booster. The advance should work in 4th gear, after a short delay, regardless.

Can you by-pass this crap? Soitanly! Is it worth it to bypass it? Probably not, unless the system has a total failure, and you just don't want to fix it. There's really only 3 parts here. The solenoid, the temp sensor, and the delay relay(73). It's really pretty simple, and all of the parts are available.

As always... Joel.. you are d Man..     That sure does explain it.. I will check it out this weekend.... That should equate to about 25 posts and maybe a couple dozen votes in the car show....   juzz kiddiin, but I really do appreciate that explanation... 2 cruzn2006-12-20 18:03:00