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ray_mcavoy · 07-18-2018, 11:46 PM

That temperature switch on the passenger side cylinder head is likely for the TCS (Transmission Controlled Spark) system. It was an early emissions system used on some of these trucks that blocked vacuum from reaching the distributor vacuum advance until the transmission was in high gear (used with both manual & automatic transmissions). The system used a temperature switch so it was only active once the engine was up to operating temperature.

Trucks with TCS, a small block V8, and factory gauge cluster usually had the temp sender for the gauge located on the driver side cylinder head and the temp switch for the TCS on the passenger side cylinder head.

07-18-2018, 11:46 PM	#8
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,358	Re: 1970 350 Temp Ports ? That temperature switch on the passenger side cylinder head is likely for the TCS (Transmission Controlled Spark) system. It was an early emissions system used on some of these trucks that blocked vacuum from reaching the distributor vacuum advance until the transmission was in high gear (used with both manual & automatic transmissions). The system used a temperature switch so it was only active once the engine was up to operating temperature. Trucks with TCS, a small block V8, and factory gauge cluster usually had the temp sender for the gauge located on the driver side cylinder head and the temp switch for the TCS on the passenger side cylinder head.