joshduty

Does anyone know what this part is? Its of a 1970 Cutlass with a 4 barrel 350. I cannot for the life of me figure it out. Is it some kind of air flow sensor?

Thanks for the help!

VC455

That is an electrically-controlled vacuum solenoid that opens/closes depending on the current gear in the transmission.

The vacuum being controlled goes to the distributor vacuum advance. The purpose is to eliminate vacuum advance at idle and low speed (for emission control).

Refer to page 6C-18 in your 1970 Chassis Service Manual.

scrappie

I'm gonna guess TCS (transmission controlled spark) switch.

rocketraider

TCS solenoid/switch as Scrappie said. Gary explained its function.

It alters vacuum signal to distributor vacuum advance depending on 1) engine temperature and 2) what gear the transmission is in. It shuts off vac advance unless the transmission is in high gear.

Most people disconnect and bypass it unless they're going for a high-point restoration.

dragline

Excellent picture of original hose/wiring routing. You can get that TCS switch new if yours needs to be replaced.

https://www.ebay.com/itm/27142874315...4aAtQjEALw_wcB

VC455

Dean's right.

And consider that there is one condition where you might want to keep it...

It retards the timing at idle, which puts an artificial load on the engine. This results in less hydrocarbon emission (reduces stink of the exhaust). If that matters to you, follow the factory tune-up instructions.

Fun71

Apparently folks have done that since these cars were new. My Dad bought a 1970 Supreme 350-4bbl in 1977 from the original owner and that switch was not present even way back then.

joshduty

Thanks for the link... I think I may order another since it appears there are pieces that are broken on it.