Correct th400 kickdown switch for 70 bb

[kaphillips]

I have a 70 cst big block 1/2 ton truck that is missing the carb mount kickdown switch for the th400. My question is did all 70 big block use a unique 4 barrel connector switch on the carb that had spark arrest. Are did some 70 have no spark arrest and use the more common carb mount 2 spade connectors. Can multiple people with 70 big blocks see what is original for me. Spark arrest type or non spark arrest carb mount switches. Thanks people. Pictures would be greatly appreciated.

[67ctener]

I'm not sure what year they switched but mine is out of a 71 and its an electronic kick down mounted on the gas pedal

[SS Tim]

Where are you getting "spark arrest" from? All the factory engine mounted kick down switches I recall seeing are the same big block or small block. A rubber weather booted switch with two electrical contacts.
Both of those connectors are seperate single lug connectors.
What do you have? How about a picture or two?

[kaphillips]

Ok I was referring to transmission controlled spark (TCS). What year was it installed, did all big block TH400 70 models have it, what hardware did it consist of, what was its purpose.

[SS Tim]

TCS was introduced fro the 70 MY and my references state all C10s with vacuum advance were so equipped. In a nutshell it prevents spark advance in any but high gear or reverse. In this way it reduces exhaust emissions, mostly NOX IIRC.

There is a lot already posted on the board and I know I have with people wondering what the relays and extra wires are for 70-72.

At this point I suggest reading up in the factory service manual in section 6Y about the emission controls then get back with questions.
Maybe even just start a new thread on "70 TCS installations and operation".

RTFM ... Read The Factory Manuals... download 'em here

[davepl]

My 70 402-TH400 Longhorn had the four barrel connector, though I just assumed it was kickdown. I do not recall any interface to the coil or distributor, though there could have been and I just missed it.