tcs
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Depends on your state. It is a pollution control device and some states like CA outlaw messing with them.
I have mine bypassed on my '72 but everything is there should I want to hook it up for a show or something.
Here's what it does, by not allowing vacuum advance, it raises the temperature of the engine which causes it to burn the fuel more completely.
I don't know about the '74 but on the '72 vacuum advance is only allowed in 4th gear. It is controlled by a switch in the 3-4 shift lever housing with a ground wire attached to it. The switch is designed so that it only contacts the transmission case in 4th gear which completes the circuit by grounding it out thereby allowing vacuum advance to pass through the solenoid mounted on the intake manifold.
In order to bypass the TCS system, disconnect the tube from the distributor vacuum advance can and run a new tube from there to a manifold vacuum port on the carburetor. Then disconnect the tube from the metered vacuum port that originally served as the vacuum source for the TCS solenoid and cap the port.
Since the car was set up to run off of a metered vacuum port and you now have vacuum advance available at all times you will need to re-adjust the minimum idle speed.
cc
I have mine bypassed on my '72 but everything is there should I want to hook it up for a show or something.
Here's what it does, by not allowing vacuum advance, it raises the temperature of the engine which causes it to burn the fuel more completely.
I don't know about the '74 but on the '72 vacuum advance is only allowed in 4th gear. It is controlled by a switch in the 3-4 shift lever housing with a ground wire attached to it. The switch is designed so that it only contacts the transmission case in 4th gear which completes the circuit by grounding it out thereby allowing vacuum advance to pass through the solenoid mounted on the intake manifold.
In order to bypass the TCS system, disconnect the tube from the distributor vacuum advance can and run a new tube from there to a manifold vacuum port on the carburetor. Then disconnect the tube from the metered vacuum port that originally served as the vacuum source for the TCS solenoid and cap the port.
Since the car was set up to run off of a metered vacuum port and you now have vacuum advance available at all times you will need to re-adjust the minimum idle speed.
cc
Last edited by CCrane65; May 21, 2009 at 11:39 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
It is an emissions reduction device. If you run the engine 'hotter', it will burn more emissions. So, GM decided to retard the spark by shutting off vacuum to the distributor advance can...but only in the lower gear ranges. TCS was switched "OFF" in high range with a [cut-oof] switch mounted to the transmission. And, yes, you can remove it. But, the better alternative is to leave it all in place and just "bypass" it (by running another vacuum line from a manifold vacuum fitting on the carb directly to the dist advance can). That way, you can run without TCS most of the time, but hook it back up for car shows and/or getting your car emission checked [if you need to do so].
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
My choice was to bag it and tuck the wiring neatly away. As stated run the vacuum advance hose from the distributor can to manifold vacuum. This did require some carb/timing/tuning work but the car runs very well.
