Purpose of spark TVS and finding a replacement

[Aaarrghh]

Hi, I'm interested in getting the best gas mileage possible with my '83 350, while keeping the stock emissions setup. It has a relatively simple emissions system. The portion I'm focusing on controls timing advance, as in the photo below. The motor seems to run well, getting an average 11 mpg, but I think my smallish RV should do better. The cap, rotor, and vacuum advance are new, stock.

In the picture, the 2 hoses attached to the check valve both go the the spark TVS on the thermostat housing. The immediate problem is that one vacuum hose coming out of the spark TVS is old and cracked, but it's glued in, so I can't replace it. I'd like to find a new ported vacuum switch, to solve that issue and to know the switch is working properly. I've read that these switches have stems that can break, and if this one does, it can have a bad effect on mpg. Mine is 33 years old, now.

But finding the correct replacement part doesn't seem to be easy. I've searched Google, and the usual parts houses online, and found lots of TVS's, but few of them tell what the color code is, or what the operating temperature is. Heck I don't even know what the temperature range is of my original. All I know is the top is white. I don't want to put on one that's wrong. Can someone help with this?

Also, and I know this is getting a bit esoteric, but what does this arrangement do? Coolant temperature is the controlling factor. Maybe I should ask, what would happen if I just bypassed the system altogether, with a vacuum hose straight from the carb to the distributor, maybe keeping the delay valve?

[EldoradoBill]

You need the delay so you don't get preignition from the combination of too much vacuum advance and lean fuel mixture, which can happen by nature of how the vacuum secondaries operate on the Quadrajets. As for the vacuum switch I'd try and slit the old hose off with a razor knife, or cut the old line and sleeve a new line over it because chances are it will snap in the T-stat housing and the bolts holding the housing on are probably rusty and crusty and I see a big mess heading your way...


Bill

[Aaarrghh]

Sleeving on a new line is a great idea  D:oH! .  Thanks!