[sglemans]

I was looking for the engine code by the distributor and I saw this device with an open vacuum port. Anyone know what this is and where it attaches to?

Also, anyone see an "SW" under the vacuum nipple? (Have to look closely) I wonder what that's for

[Shiny]

May be a TCS (transmission controlled spark) solenoid. I know my 70 350 has one, but I bypassed it.

It was an emission control scheme that limited vacuum to the advance can until the transmission was in 3rd gear.

Here was a listing for one in an older thread:

https://forums.maxperformanceinc.com...d.php?t=844904

Here's a photo from that listing (tnx to pontiacman).. does your part look like this?



Here's a description of the function from Kenth in another thread:

https://forums.maxperformanceinc.com...1&postcount=17

Mike

[Joe's Garage]

That's definitely the TCS solenoid.

Early 70s smog stuff.

We normally bypass them, too.

[sglemans]

Where would the vac line go on the other end, per factory setup? I just want to be sure there's no open vac lines anywhere.

[sglemans]

Shiny, I think that's it but I'm pretty sure it has just 1 nipple, not 2 as in the pic. Will have to check again though

[Joe's Garage]

The vacuum hose from the fitting in the rear base of the carb goes to the single hose fitting sticking straight out the end with the wiring harness plugged into it - usually at the front. This needs to be FULL manifold vacuum.

The vacuum hose to the vacuum advance can in the distributor goes to the side-facing nipple on the 'T' fitting at the opposite end - usually the rear. The other side of that fitting - the straight out the back one - has (or had) a little square foam filter over it to filter the air going back into the hose and vacuum advance when the solenoid turns the advance off. It basically keeps the dirt out.

When the engine temp is under 85* or over 220*, the 3-prong temperature switch in the water crossover at the front of the intake activates the solenoid and allows vacuum to fully advance the vacuum advance portion of your timing.

When the engine temp is between 85* and 220*, you need to be in high gear and the switch on your manual transmission sideplate or on your auto transmission speedo cable will activate the solenoid and allow full vacuum advance.

Here's a pic with an explanation.

[sglemans]

Thx Joes Garage for that info. I guess mine is disconnected, does it have any negative effect if it's not connected? Do you have to change timing or any other adjustments?

[Schurkey]

Originally Posted by sglemans

I guess mine is disconnected, does it have any negative effect if it's not connected?

Tampering with emissions-control devices is illegal under Federal law.

OTOH, your engine will run better, cooler, and more fuel-efficient with it bypassed.

Originally Posted by sglemans

Do you have to change timing or any other adjustments?

No. Same deal...illegal under Federal law, but since the Feds don't do emissions testing unless they REALLY want you, you might want to optimize the ignition advance anyway.

[sglemans]

Yeah, if tampering with emission controls was enforced then half the car shows would be going to iron-bars right now