Vacuum control valve for a 1971 cutlass w/ 350
December 22nd, 2009, 06:40 PM
#1
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Vacuum control valve for a 1971 cutlass w/ 350
Anyone know where I can get an OEM distributor vacuum control valve for a 1971 cutlass w/ 350? It seems that most of the after market ones dont have the connection for the harness that connects to the original. I know it can be bypassed but I want to use it.
December 22nd, 2009, 07:21 PM
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You must be referring to the transmission controlled spark (TCS) unit. I have not seen these new, so a used one would be your best bet. I am sure someone on this forum has some in their junk boxes.
December 22nd, 2009, 08:36 PM
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I foud this in my shop manual. It looks like the 442' and 4 barrel carbs came with a TCS... My 2 barrel came with the Distributor Vacuum control Switch which has to do with more than emissions. It appears that it helps cool the engine and also helps advance the timing. I attached the page from my book showing the difference.
December 22nd, 2009, 08:46 PM
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Actually what I need is the part in the picture above the one with the TCS. I need the distributor vacuum control switch. I hac a 2 barell carb and it has that instead of the TCS. I think the TCS is built into it.
December 22nd, 2009, 08:57 PM
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It appears that the manual trans cars had a different style of TCS.
Its primary purpose is emission control. Limiting advance in 1st or 2nd gear can cause the engine to run hotter, reducing NOX (hope I remembered right). If it runs too hot, the system senses the high temp and applys advance regardless of gear.
When these are bypassed, manifold vac is often connected right to the disty...
Distributor vacuum control switch is the same as the TCS units on these cars, not sure why the diff't names listed for each type. Page 6C-8 interchanges the name TCS.
The one you picture is correct, as you have auto and air cond.
Its primary purpose is emission control. Limiting advance in 1st or 2nd gear can cause the engine to run hotter, reducing NOX (hope I remembered right). If it runs too hot, the system senses the high temp and applys advance regardless of gear.
When these are bypassed, manifold vac is often connected right to the disty...
Distributor vacuum control switch is the same as the TCS units on these cars, not sure why the diff't names listed for each type. Page 6C-8 interchanges the name TCS.
The one you picture is correct, as you have auto and air cond.
Last edited by Lady72nRob71; December 22nd, 2009 at 09:03 PM.
December 23rd, 2009, 07:20 AM
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Distributor Vacuum Control Switch
All cars equipped with air conditioning or heavy duty cooling and all 455 Cu. In A Bodies and Toronados will have a distributor vacuum control switch assembly. This unit is used to advance the ignition timing when the transmission is in third or fourth gear or when high coolant temperatures are encountered at idle. (Fig. 6K-10)
With the transmission in first or second gear the solenoid is energized, the valve plunger is sealing off port "C" (carburetor), opening port "V" (vent) to atmosphere depleting any vacuum that might be present in the vacuum advance unit. In third or fourth gear, the solenoid de-energizes allowing the valve plunger to move down sealing off the valve port. When this happens, vacuum is directed from the carburetor through port "C" and out port "D" to the carburetor vacuum advance.
When the engine coolant temperature reaches 210 degrees F., the valve plunger begins to move upward sealing off the vent port and opening up port "MT" (manifold). At 218 - 224 degrees F., full manifold vacuum is directed to port "D" (distributor) and the vacuum advance unit regardless of transmission mode.
All cars equipped with air conditioning or heavy duty cooling and all 455 Cu. In A Bodies and Toronados will have a distributor vacuum control switch assembly. This unit is used to advance the ignition timing when the transmission is in third or fourth gear or when high coolant temperatures are encountered at idle. (Fig. 6K-10)
With the transmission in first or second gear the solenoid is energized, the valve plunger is sealing off port "C" (carburetor), opening port "V" (vent) to atmosphere depleting any vacuum that might be present in the vacuum advance unit. In third or fourth gear, the solenoid de-energizes allowing the valve plunger to move down sealing off the valve port. When this happens, vacuum is directed from the carburetor through port "C" and out port "D" to the carburetor vacuum advance.
When the engine coolant temperature reaches 210 degrees F., the valve plunger begins to move upward sealing off the vent port and opening up port "MT" (manifold). At 218 - 224 degrees F., full manifold vacuum is directed to port "D" (distributor) and the vacuum advance unit regardless of transmission mode.
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