i have a STOCK 1970 cutlass 350/350. This is on the passenger side of the carb the vac lines going to it and from it goto the carb. It's broken and I don't know what it is to fix it. Can anyone help or do I just need to plug the vac lines and get rid of it?

 

I read your post yesterday but was waiting for someone to chime in as I am not sure what it is. Is there also a wiring plug attached to it with two wires? For the life of me I can't remember seeing something like that on an early seventies small block. At any rate, I want to welcome you to our site and hope that someone comes up with an answer for you.

 

It appears to be an electricly operated vacuum valve. Dont know its purpose....the factory shop manual would tell you.

 

i guess that i need to do some more looking around. My father bought this car new in 70 and has kept it as stock as he could. the car has been sitting up for about 6 or 8 months. i have been trying to get it to run better. it had a back fire while driving at a steady med throttle and would only do it once or twice during a drive around town. i have changed the plugs and started looking around and i found that vacuum valve broken on the back side. there is what looks like a needle valve inside. thanks for your help.
Chris

 

I had a 70 Chevy with the same switch on it. It does control the vacuum advance by letting vacuum run through the switch when power is applied to it. I believe it has something to do with emissions. You might want to try a piece of vacuum hose and connect it from the carb to the advance directly and see if it makes any difference. Hope that helps.

Darrell

 

Who's got a 1970 Chassis Service Manual handy? I've misplaced mine but am sure it would explain this part and what it does!

 

That is a TCS solenoid (transmission controlled spark) It is an anti-pollution device. Do a search and there is plenty of info on it, the Auto Zone repair section shows it too. It vents the distributor advance to disable it in certain gears. If it isn't working correcly you get no advance , the reason for the backfire. You can bypass it, connect a hose directly from the carb where the one end is now to the vacuum advance. Hope this helps.

Allan

 

That doesn't seem right, a TCS on a '70??? That may not be an original engine then. Would that be a possibility?

 

Dan, I think Allen's right. I know California emissions cars had smog stuff back in 1967 for sure, maybe earlier. I've dismantled a couple 1970's with these valves on them that I believe is factory. John

 

Ahhhh so, California. Nuff said.

 

thank for the help guys. i think that i will try to bypass it. by the way this is a nashville tn car.

 

I have heard that some 67 cars also had A.I.R. pumps as well. Again, California.

John

 

Hey Turbo,
That is the T.C.S. Solenoid.

On my 70 442, 4spd, there is a small switch on the side of the transmission. When in 4th gear, that little switch sends 12 volts to the TCS solenoid which then is supposed to open. From what Ive read, when in 4th gear, this sends vacuum to the distributor and advances the timing, supposedly giving better fuel economy when in a "highway gear".

When I bought by car 3 years ago, that little gadget was missing. I need to find one and then need a little guidance as to where the vacuum lines route to. Cant seem to find anything in the assembly manual.

Does yours look like its hooked up "factory"? If you could let me know which vac line runs where, that would be helpful.

 

Isn't it amazing the amount of emissions control devices that have been used on cars over the years?

 

For some reason there seems to be an epidemic of TCS questions on the various Olds boards recently. A short tutorial is in order. In order to reduce NOX emissions, automakers disabled the vacuum advance in the lower gears. This started in the 1970 model year. The TCS solenoid is simply a switch that disables the ported vacuum source until the trans switch makes contact in high gear. This opens the valve and allows the vacuum advance to function (hence the TRANSMISSION CONTROLLED spark). The problem with disabling the vac advance is that under certain conditions the car can overheat. This is why the ported vacuum output from the TCS is run through the thermo vacuum switch (TVS) located at the front of the intake. The TVS has one output to the distrubutor vac advance (the D port), an input from the ported vac from the TCS switch, and another input from straight manifold vacuum. Under normal conditions, the ported vac is routed to the distributor and the manifold vac port is closed off. Under overheat conditions the manifold vac port is connected to the distributor and the ported vac port is closed off. In 1971 the TCS was mounted on the top of the TVS to create a single valve. Some of these also have a fourth port that simply vents the distributor vac advance canister when the TCS valve is closed.

 

So, unless you are restoring the car, live in a state that inspects for those items, or want to reduce NOX emisions, you really don't need to comb the universe for one of these little gizmos, right? I mean, it seems to me that the effort has more negative side effects than the positive effect or reduced NOX emissions. Yes, I am not green conscious, seems sort of un-compatible with the image of a Hot Rodder in my opinion.

 

Joe that is a pretty cool explanation. I wish I had a schematic so it would make more sense; however, it is sort of a mystery to me that Detroit would put an emissions control device on a car to lower NOx emissions that could cause overheating. Didn't they use EGR to lower combustions temperatures which would in turn lower NOx? It seems to me that something that would cause the car to overheat in certain conditions would raise NOx emissions... Or am I missing something? I am just trying to remember all of the emissions control stuff I learned in school and that was years and years ago.

 

Yes, the overheating probably did raise NOx. The point was that for the vast majority of driving conditions, this was a very inexpensive way for Detroit to comply with the then-new federal emissions requirements. It was a pure and simply bandaid approach; there were only a few driving conditions where the loss of vac advance would cause overheating. As automakers got more savvy about emissions controls, these functions were more integrated and thus began to function better.

 

Ahh... bandaid approach. Seems like my car has seen more of that recently.