Transmission Control Spark Solenoid [Archive] - Chevelle Tech

: Transmission Control Spark Solenoid

Nick Demos
Jan 31st, 99, 5:49 PM
Can someone tell me if all 1970 SS 396ci 350hp Chevelles came factory equiped with the (T.C.S.) I see very few cars which still have these. Is that because this solenoid hurt performance. Does anyone recall seeing any articles regarding the setup/installation or restoration of this system. Any information regarding this system would be appreciated.

Jan 31st, 99, 8:04 PM
My best educated guess would be yes, that is was a factory item on all 350 hp motors. Basing that on the fact that the factory assembly manual covers it in good detail and I have a east coast built car with one and a Van Nuys built car with California smog equipment that has one.

I have seen reproduction ones advertised somewhere, just can't remember where.

I would recommend the assembly manual as it is an excellent source for a bunch of info to the restorer.

michael j
Feb 1st, 99, 7:10 AM

Yes the 70SS 396/350hp had the TCS. Yes, it is generally thought that it hurt performance. We all know the story about the guy who stripped his car of anything that he didn't think was necessary. If it didn't help you go fast than it was trash.

The parts of the system that I know about:
Solenoid - right off QJet carb, part vaccuum & part electrically operated. Effects vaccuum advance of distrib in all gears but 4th gear (for a 4sp. That is what I have, so that is what I've researched.)
Switch - On transmission. I believe is switched "ON" for 1st, 2nd, & 3rd and "OFF" for 4th.
TCS relay - on firewall connects tranny switch with solenoid

Ground Up Restorations is the ONLY source I've seen for the Solenoid. Their catalog has some pretty good illustrations of how it sets up on the valve cover and even shows you the special vac advance line clip you'll need (has 2 line running on it rather than 1.) They are a small operation, so don't expect things to go as smoothly as with Year One, but they are very good guys who will talk endlessly about your car if they could. I talk to George.

516.248.4567 (
PO Box 3402
New Hyde Park, NY 11040

Hope this helps.

I just checked their website. The TCS Solenoid illustration I reffered to is on the first page of their "Detailing" Section.

[This message has been edited by michael j (edited 02-01-99).]

Steve S
Feb 1st, 99, 8:20 AM
I have an article on TCS that states that all V8's had TCS in '70. The components of the system are: Vacuum Control Solenoid, Override relay, temp override switch and trans switch. The temp override switch was a two terminal temp switch mounted in the passenger side head. The two terminals were; one for <82 deg and one for >232 deg. They were wired together and went to the ground side of the override relay. SO that for temps less than 82 or greater than 232 the override relay would energize and disable the vacuum control solenoid and you would have full vacuum in all gears. The vacuum control solenoid was an electrically controlled vacuum switch. It had three vacuum lines going to it; one went to air cleaner for clean air vent (no vacuum), another to a manifold vacuum source on the carb and the third to the distributor vacuum port. When the engine temp was between 82 and 232 deg the override relay was off which allowed 12v ign to one side of the vacuum control solenoid. The other side of the vacuum control solenoid went to the trans switch. This switch provided a ground in gears 1 & 2 and open in 3 & 4. In gears 1 & 2 the vacuum solenoid would be enrgized and clean air(no vacuum) was ported to the dist. In 3 & 4 solenoid was off and full vacuum went to the dist.

Steve Strasemeier (70SS)

Jim Humphrey
Feb 1st, 99, 3:25 PM
Just a note: the TCS solenoid for small blocks isn't the same configuration as the big block. Different mounting provisions.

Jim H.

Feb 1st, 99, 7:20 PM
Even my 307 '70 3sp had aTCS. My 72 BB 4sp had a TCS and my 71 350 auto had a TCS. Jim is right, the BB & sm bk configuration is completely different. In Okla only 79-newer cars require an emissions inspection. TCS------bye bye, long ago. I use manifold vacuum and set up the dist accordingly.


Feb 7th, 99, 7:28 PM
TCS is BS...forget it!