Vacuum help.
Thread Starter
Registered User
Joined: Apr 2009
Posts: 27
Vacuum help.
Guys,
I have a 1972 cutlass with a 350 4 barrel. I am wanting to eliminate the vacuum switch thingy on the intake. The one with the electrical connector on top. How can I accomplish this? It appears that my kickown switch in the trans connects to it. Where should I attach vacuum lines for modulator and vacuum advance if this piece is bypassed. What about the electrical ?
I have a 1972 cutlass with a 350 4 barrel. I am wanting to eliminate the vacuum switch thingy on the intake. The one with the electrical connector on top. How can I accomplish this? It appears that my kickown switch in the trans connects to it. Where should I attach vacuum lines for modulator and vacuum advance if this piece is bypassed. What about the electrical ?
Tom Servo's Stunt Double
Joined: Apr 2004
Posts: 889
From: San Antonio, Texas
The only thing it does is keeps you from kicking it down until the engine warms up. An early emissions thing.
Feel free to unplug the electrics, plug your trans modulator line to the intake, pull that ugly thing out (save it if it looks decent...ebayers pay lotsa $ for the strangest things) get a cast plug from Home Depot, plug that puppy up and feel good about yaself!
C.J.
Feel free to unplug the electrics, plug your trans modulator line to the intake, pull that ugly thing out (save it if it looks decent...ebayers pay lotsa $ for the strangest things) get a cast plug from Home Depot, plug that puppy up and feel good about yaself!
C.J.
Old(s) Fart
Joined: Mar 2007
Posts: 50,815
From: Northern VA
This must be the week for TCS questions, which have appeared on multiple Olds forums.
Nope
Yes.
The "thing" is the thermal vacuum switch (TVS) which is part of the transmission controlled spark (TCS) system, which was an early emissions control system designed to reduce NOx emissions. The purpose of TCS was to inhibit the vacuum advance until the trans was in top gear. A switch on the trans energized the solenoid in the TVS through that connector when the trans was in high gear.
The four ports are Distributor, Carb (ported vacuum), Manifold, and Vent. In prior years, ported vacuum would be connected directly to the vac advance canister. Here, the ported vac signal is routed through the TVS first, which blocks the vacuum signal until the trans hits high gear and the solenoid is energized to open the valve. The vent port simply provides a way to vent the vacuum signal when the valve closes again. The thermal part of the TVS is designed to bypass the TCS function if the engine overheats and connects manifold vacuum directly to the distributor to increase the advance and let the engine run cooler.
Unless you care about an exact restoration, eliminate the TVS and connect the distributor directly to either ported or manifold vacuum, whichever runs better. You may need to play with the initial timing if you do this.
An early emissions thing.
The "thing" is the thermal vacuum switch (TVS) which is part of the transmission controlled spark (TCS) system, which was an early emissions control system designed to reduce NOx emissions. The purpose of TCS was to inhibit the vacuum advance until the trans was in top gear. A switch on the trans energized the solenoid in the TVS through that connector when the trans was in high gear.
The four ports are Distributor, Carb (ported vacuum), Manifold, and Vent. In prior years, ported vacuum would be connected directly to the vac advance canister. Here, the ported vac signal is routed through the TVS first, which blocks the vacuum signal until the trans hits high gear and the solenoid is energized to open the valve. The vent port simply provides a way to vent the vacuum signal when the valve closes again. The thermal part of the TVS is designed to bypass the TCS function if the engine overheats and connects manifold vacuum directly to the distributor to increase the advance and let the engine run cooler.
Unless you care about an exact restoration, eliminate the TVS and connect the distributor directly to either ported or manifold vacuum, whichever runs better. You may need to play with the initial timing if you do this.
Thread
Thread Starter
Forum
Replies
Last Post
perro
Interior/Upholstery
4
Sep 4, 2007 11:52 PM
ToronadoGuyDenver
Brakes/Hydraulic Systems
12
Mar 18, 2007 02:52 AM
