Thermal Ignition Control (TIC) Valve - do I need it?

JMC85284

New Member
Joined
May 25, 2022
Messages
11
Reaction score
64
Location
Tempe AZ
In process of changing out thermostat and hoses, I noticed this crusty old vacuum valve which the Google machine tells me is called a Thermal Ignition Control Valve or TIC valve. I found a paragraph on it in the FSM and apparently it's intended to add advance/increase idle speed if the engine gets overly hot. One of the vaccuum lines from the TIC valve goes to the vacuum advance unit on distributor, which is consistent with what the FSM said, and the other two I presume go to manifold and ported vacuum sources but I didn't trace them.

So I'm thinking of just capping this thing off and running the distributor advance directly off of ported carb vacuum. In other words, leaving valve in place but bypassing and forgetting about it. I will recheck timing etc when everything is all back together, but wanted to just run it up the C BODY flagpole and see if the collective brain trust had any thoughts on bypassing the TIC vs. keeping it alive. Car is '73 Imperial, 440 w Edelbrock 1406 carb. Thanks !

IMG_2571.jpg
 

Boydsdodge

Well-Known Member
FCBO Gold Member
Joined
May 26, 2020
Messages
784
Reaction score
1,026
Location
Toronto Canada
I did what you are planning. disconnected and plugged. Running vacuum advance from ported vacuum at carb to distributor vacuum advance can.
 

CBODY67

Old Man with a Hat
Joined
Mar 27, 2011
Messages
7,778
Reaction score
4,879
The TIC valve was added in mid-year '72 as a part of a recall campaign on the a/c systems. As the '72s were built, it was possible for hot air from the radiator to be recycled back into the a/c condenser/radiator IF there was a strong enough tailwind. When that happened on a very hot day, then the a/c freon pressures would increase enough to blow a hose, so the TSB claimed. I suspect this failure usually happened at idle in traffic or similar.

The FIX? They installed die cut pieces of thin rubber to the front valance panel and the sides of the radiator/condenser, such that all of the air getting to the condenser came through the grille area only. When the engine started to overheat, the TIC valve would open and supply straight manifold vac to the distributor vac advance to speed up the engine a bit, so the fan would run faster and draw more air through the condenser/radiator and help cool things off a bit. When things cooled down, then the TIC closed and things went back to normal (ported vac to the dist).

We got the campaign done to our '72 Newport Royal 400-2bbl when the TSB was issued. I could tell no difference, one way or the other afterward.

I would go ahead and remove the TIC valve and screw a pipe plug into the hole. With a shot of engine paint, of course. Unless somebody is looking, they would never miss it, I bet. Run the dist vac line from the ported port on the carb and be done with it. It could well be that that Thermal Vacuum Switch has been long-discontinued anyway (although GM used something similar for other functions in the '70s and '80s).

Just some thoughts,
CBODY67
 

1970FuryConv

Senior Member
Joined
Aug 8, 2014
Messages
4,772
Reaction score
4,422
Location
Richmond, VA
In process of changing out thermostat and hoses, I noticed this crusty old vacuum valve which the Google machine tells me is called a Thermal Ignition Control Valve or TIC valve. I found a paragraph on it in the FSM and apparently it's intended to add advance/increase idle speed if the engine gets overly hot. One of the vaccuum lines from the TIC valve goes to the vacuum advance unit on distributor, which is consistent with what the FSM said, and the other two I presume go to manifold and ported vacuum sources but I didn't trace them.

So I'm thinking of just capping this thing off and running the distributor advance directly off of ported carb vacuum. In other words, leaving valve in place but bypassing and forgetting about it. I will recheck timing etc when everything is all back together, but wanted to just run it up the C BODY flagpole and see if the collective brain trust had any thoughts on bypassing the TIC vs. keeping it alive. Car is '73 Imperial, 440 w Edelbrock 1406 carb. Thanks !

View attachment 548170
I vote Bypass. Ported vacuum always works for me. TIC is useless, especially with cars this old.
 
Top