'71 TCS Question

[Mark H.]

No TCS on my car since I bought it in 2007. Temp switch and green wire is there.
Newly rebuilt 7041213 DM Q-jet. Thinking of installing the TCS that belongs on it.


Here's my question...

Does the TCS that is supposed to be on my '71 SB A/C car also increase idle speed when the temperature switch in the RH cylinder head goes over a certain temperature to pull more air through the radiator during city type driving conditions?

My '88 L98 had a temperature switch in the head that would turn on the electric radiator fan at 238* and then off at 215*.

I know about the operation of the TCS as far as the vacuum advance below 82* and in 3rd-4th gear positions, but am most curious about its operation as mentioned above in high temperature situations.

Thanx,

Mark

[Pat M.]

Re: '71 TCS Question

Does the TCS that is supposed to be on my '71 SB A/C car also increase idle speed when the temperature switch in the RH cylinder head goes over a certain temperature to pull more air through the radiator during city type driving conditions?

Mark that's how my 70's TCS works and I believe yours should too.

[Duke W.]

Re: '71 TCS Question

I believe what it does is apply vacuum advance at idle. This increases total idle advance to initial plus full vacuum advance, which reduces EGT by several hundred degrees and also increases idle speed (without moving the throttle valves) since more of the fuel's energy is being turned into useful work to overcome engine friction rather than being thrown out the exhaust, and the higher speed increases fan flow.

Vintage Corvette engines need low twenties to low thirties total idle spark advance to minimize idle fuel flow and EGT. Greater valve overlap increases the idle spark advance requirement since exhaust gas dilution slows flame propagation speed, so base engines work best with low to mid twenties and SHP engines high twenties to low thirties.

The reason emission controlled engines don't have vacuum advance at idle is to keep EGT high to promote oxidation with injected air and/or to keep the catalyst bed hot enough to promote reactions.

Unfortunately it takes more fuel to maintain high EGT for low emissions, so less than optimum idle spark advance is a requirement, and since it increases EGT more heat is rejected to the cooling system as the hot exhaust passes through the head exhaust port, so there is more tendency to overheat in hot weather low speed driving.

The high idle coolant temperature TCS override protects the engine from overheating in extreme conditions.

Duke

[Alan S.]

Re: '71 TCS Question

Hi Mark,
I believe the system on 71 model year cars was called a 'Combined Emission Control' system and was somewhat different than the systems used for the 70 and 72 model years.
Member Jack Humphrey wrote a article that was published in the RESTORER that describes the parts to the system, it's intended operation, and trouble shooting information. It's in Volume 35, Issue 4, pages 44-48. It's PRICELESS for 71 car owners.
If you don't have access to it let me know.
I'm not sure just what hardware or wiring an a/c car may have had in addition to the CEC solenoid on the carburetor, and the delay relay and reversing relays mounted on the firewall.
Regards,
Alan

[Mark H.]

Re: '71 TCS Question

Thank you all. Allen those are exactly the pics I wanted to see. I do have the article you referenced. Page 3 I think. Tracking wires and locating a switch.Mark

[Paul O.]

Re: '71 TCS Question

Mark

The 1971 CEC has 5 basic components the 1 Solenoid, 2 relays and 2 switches.

1. The first relay is a time delay relay upon each engine start for 15 sec this relay sends power to the solenoid for vacuum advance and a slight push to the throttle.
2. The second relay is the reversing relay it sends power to the solenoid when the car is in 3rd and 4th gear through a ground provided by the transmission switch.
3. The RT head temperature switch provides ground in case engine temp exceeds a set value giving an Rpm increase through vacuum advance and slight throttle opening. This causes an increase in air flow over the radiator thus cooling down engine coolant.
4. The transmission switch gives ground in 3rd and 4th gears a described earlier.
5. The solenoid is a duel function unit for vacuum advance and slight throttle movement to increase RPM and emission controls.

Paul 18046

[Mark H.]

Re: '71 TCS Question

Excellent! Just what I was looking for. Under extreme bouts of sluggish traffic conditions I have experienced stalls. Very rarely, and only when I'm at a virtual standstill. If I don't apply slight pressure to the gas pedal to increase RPMs, it'll stall. Not impossible, but tough to do on an incline with a 4spd.


Thank you all very much. Looks like I have everything in place except the solenoid itself, the bracket and the stud/manifold bolt it attaches to.

Mark

[Alan S.]

Re: '71 TCS Question

Hi Mark,
I'd be interested in seeing a picture of your 'delay' relay. It's the one closest to the firewall.
I've seen at least two configurations; one as shown in my picture that's very similar to the reversing relay in front of it, and another that actually looks more like a tiny kitchen toaster. Yours?
Regards,
Alan

Here's a picture of the 'toaster' version:

[Mark H.]

Re: '71 TCS Question

Okay,

After pouring over the CSM Electrical Diagrams (Fig 96), I located the harness for the CEC solenoid by wire colors. It was long enough to be hidden under the vacuum hoses and hanging down next to the washer fluid bag.

It seems I have everything in place except for the solenoid, bracket, manifold bolt/stud and the metal vacuum tube that goes to the distributor.
Guess the clamp on the RH side of the intake manifold is to hold the metal vacuum tube.

Here are the relays Alan. Excuse the pollen and dirt, but I've been putting a few miles on it.

The 3rd relay must go with the Kill-Switch (toggle) that I have under the dash from a previous owner. It allows the starter to crank but no spark. A guess.

Mark

[Paul O.]

Re: '71 TCS Question

Mark

If you have power windows I think that is the relay for that.

Paul 18946

[Mark H.]

Re: '71 TCS Question

Mark

If you have power windows I think that is the relay for that.

Paul 18946

Yes I do Paul.

[Paul O.]

Re: '71 TCS Question

Mark

Sorry should have said Circuit Breaker for power windows.

Paul 18046

[Mark H.]

Re: '71 TCS Question

Finding a CEC solenoid and bracket for a '71 is proving difficult so far from the usual suspects. Other years seem to be no problem.

Any ideas?

[Alan S.]

Re: '71 TCS Question

Hi Mark,
Yes the solenoid is a bit rare but they are around. The mounting brackets are easier to find. Some of the vendors have them (ZIP, for one).
Thanks for the picture of the 'delay relay'; it looks like the 'toaster' version. If I remember our cars were built fairly close together. Mine was mid-January.
Again, thanks for the pictures.
Regards,
Alan

[Jim M.]

Re: '71 TCS Question

The part number for the solenoid is 1114444 and there always 4 or 5 of them for sale on fleabay with varying prices and cosmetic appearance.