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Old 07-12-2019, 06:21 PM
tjs72lemans tjs72lemans is offline
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Default TCS switch bypass

If one wants to unplug and bypass the electronic portion of the TCS switch and use just vacuum to control it, how is it plumbed? There are 3 ports on TCS switch. Would one go to carb and one to distributor? Which port plumbs to what vacuum?

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Old 07-15-2019, 01:24 PM
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Originally Posted by tjs72lemans View Post
If one wants to unplug and bypass the electronic portion of the TCS switch and use just vacuum to control it, how is it plumbed? There are 3 ports on TCS switch. Would one go to carb and one to distributor? Which port plumbs to what vacuum?
Leave everything connected including the vac hoses except disconnect the solenoid electrical connection. You should have vac advance all the time.

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Old 07-15-2019, 08:11 PM
tjs72lemans tjs72lemans is offline
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Thanks for that info. But, this motor was in pieces when I got it. Trying to figure out how the rest of these things hook back up. So, I have three ports for vacuum on the TCS. One obviously goes to manifold or carb , one I can only assume goes to distributor. The third must be capped? My tranny will then just have the modulator vacuum line to carb to control then, correct?

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Old 07-15-2019, 09:13 PM
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The nipple facing the firewall goes to the carb, the one on the side goes to the distributor, the other is capped by a foam filter. Its just a vent.

That's for 72 cars.


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Old 07-15-2019, 09:24 PM
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Old 07-15-2019, 09:42 PM
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Keep in mind that if you dont energize the solenoid and you hook up the dist vacuum to the solenoid, you wont have any vacuum distributor advance. The solenoid is activated and provides dist vacuum only when specific parameters are met. Emission controls.

Either you hookup the entire TCS system or you dont. Half the system wont work properly.

Quote:
Originally Posted by necdb3 View Post
Leave everything connected including the vac hoses except disconnect the solenoid electrical connection. You should have vac advance all the time.
Correct me of I’m wrong, but pretty sure its the around way around. The solenoid will provide vacuum only when emission controls parameters are met. Think of it as a normaly closed valve.

Quote:
Originally Posted by tjs72lemans View Post
My tranny will then just have the modulator vacuum line to carb to control then, correct?
The vacuum modulator only affects shift points with the use of engine vacuum.


Last edited by MescaBug; 07-15-2019 at 09:49 PM.
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Old 07-16-2019, 08:01 PM
tjs72lemans tjs72lemans is offline
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Thank you for the valuable info. Is it better not to use this TCS at all? Just hook the vacuum adv to the carb?

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Old 07-16-2019, 08:22 PM
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Yes. TCS was strictly for emission control.

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Old 07-16-2019, 09:25 PM
tjs72lemans tjs72lemans is offline
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Thank you. I may just leave it on the intake as part of original equipment, but not use.

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Old 07-18-2019, 04:42 PM
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I just checkad my car today and the solenoid closes the vacuum when actuated. At least on my -70 GTO.
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Old 07-18-2019, 08:37 PM
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Quote:
Originally Posted by MescaBug View Post
Keep in mind that if you dont energize the solenoid and you hook up the dist vacuum to the solenoid, you wont have any vacuum distributor advance.




The solenoid is activated and provides dist vacuum only when specific parameters are met. Emission controls.

Either you hookup the entire TCS system or you dont. Half the system wont work properly.



Correct me of I’m wrong, but pretty sure its the around way around. The solenoid will provide vacuum only when emission controls parameters are met. Think of it as a normaly closed valve.



The vacuum modulator only affects shift points with the use of engine vacuum.

IIRC when the solenoid is de-energized, Vac passes through. That way when the car is in 4th gear the solenoid is off. That way, you can also control turning the solenoid off with either the hot or ground side. Take either ground or power away and the solenoid turns off giving advance. The trans switch on a 4spd is grounded UNLESS it's in 4th gear. Take the ground from the solenoid and it turns off, giving advance. That's why I said to just unplug the solenoids electrical connection to give continuous adv. The solenoid on the vac side is normally open, power and ground close the solenoid vac passage.


Last edited by necdb3; 07-18-2019 at 09:11 PM.
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Old 07-19-2019, 08:14 AM
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Ok so its the other way around I was thinking, lol.

Thanks. Good to know.

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Old 07-19-2019, 09:34 PM
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Quote:
Originally Posted by tjs72lemans View Post
Thank you for the valuable info. Is it better not to use this TCS at all? Just hook the vacuum adv to the carb?
Well, yes and no. It really depends on your combination.

The idea with TCS was certainly to help emissions, but also to restrict vacuum advance until high gear, thereby limiting the potential for detonation, etc... Once you're in high gear, and (theoretically) cruising down the road without much engine load, the vacuum advance comes in improving performance, emissions and gas mileage.

The danger of going without TCS is that you will have vacuum advance under all conditions, and that may not be what you want. Too much advance under part throttle/high load conditions can lead to detonation and possible engine damage.

Of course if you hear detonation, you can always stab the throttle thereby killing off the vacuum advance, but it requires being aware of and listening to what your engine is doing. The average new car buyer may not have been so astute, so TCS helped alleviate the potential for engine damage while only sacrificing some performance in lower gears.

Personally, I don't use the TCS in my 72, but I also run higher octane gas and I watch and listen closely to my engine.

Hope that helps.

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Last edited by Mister Pontiac; 07-19-2019 at 09:39 PM.
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Old 07-19-2019, 10:50 PM
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Quote:
Originally Posted by Mister Pontiac View Post
Well, yes and no. It really depends on your combination.

The idea with TCS was certainly to help emissions, but also to restrict vacuum advance until high gear, thereby limiting the potential for detonation, etc... Once you're in high gear, and (theoretically) cruising down the road without much engine load, the vacuum advance comes in improving performance, emissions and gas mileage.

The danger of going without TCS is that you will have vacuum advance under all conditions, and that may not be what you want. Too much advance under part throttle/high load conditions can lead to detonation and possible engine damage.

Of course if you hear detonation, you can always stab the throttle thereby killing off the vacuum advance, but it requires being aware of and listening to what your engine is doing. The average new car buyer may not have been so astute, so TCS helped alleviate the potential for engine damage while only sacrificing some performance in lower gea


Personally, I don't use the TCS in my 72, but I also run higher octane gas and I watch and listen closely to my engine.

Hope that helps.
TCS is purely an emission control device. It simply doesn't allow vac adv at idle or in lower gears, to lower HC emissions. Removing it, will only increase performance. The engines prefer more timing in those scenario's and are more responsive but emissions are higher. detonation should not be a problem.

While they do run better with it disconnected, I run mine with it connected because I'm just a nut for everything to work.

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Old 07-20-2019, 12:26 PM
tjs72lemans tjs72lemans is offline
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Thanks for the insight.

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