Projects

Research Topic: 1970 TCS Relay

The TCS (Transmission Controlled Spark) relay was introduced during the 1970 model year.

There were:

two types of relays used. The 3983958 and the 961573. Each were date coded with very small numbers stamped into the case.

two different mounting methods for each different relay. On the firewall and on the wiring gutter.

three different fasteners used. Rivets, Screws, and plastic clips or plugs.

Simply, the relay was used in conjunction with a transmission switch, a vacuum solenoid, and temperature switch. It varied the amount of vacuum sent to the distributor to aid emissions.

Research Goal:

Determine what VIN / Body Number range was used for each of the relay changes.

Here is a short set of pictures that details the Nova TCS Relay, Wiring Gutter and the Rivets that fasten them together.

This first sections covers the small TCS Relay 3961573. I do not have a large one yet. This style relay was interchanged with the larger 3983958 relay. I have not figured when they were switched or when or why they were screwed to the firewall. Click here to see the other attachement styles.

The first picture shows two OEM gutters compared to the two available reproductions. The reproductions do not have the holes punched in them. The holes can be punched with a leather punch, the same goes for the radio ground slot, just use a buckle punch.

The holes across the top are the following sizes.

3/16" x 5/15" for mounting to the firewall.

The slot for the radio hood ground is 1/4" x 1/2"

The relay mounting holes are 1/4" in diameter. Punched 1 1/8" on center a part.

The left set are 7/8" from edge to center.

The Right set are 2" from edge to center.

Note the curve in the OEM gutters and the corners in the reproductions.

Here is a close up of the relay and the rivets. The realy on the left was media blasted and is bare metal. The one on the right is the original cad plating with the rust patina.

The left one was riveted in the holes exactly. The right one is the typical mispunched installation. Note the plastic still in the tubular rivet.

The relays are also date coded. The right one dated 12-9 was installed the 2nd week of January 1970.

Here are close ups of the OEM rivets and the replacement rivet and washer. the washer ID is a bit small and needs to be drilled out to fit on the rivet.

Here is a large picture of the TCS rivets and washers.

Here is an example of the early TCS relay with the plastic clips used to attach it to the gutter instead of rivets. This most all early 1970 model year cars used the clips until around December of 1969.

Nova Research Project now has Correct TCS Relay Rivets and plugs.

Available in limited quantities, the correct shape and finish TCS Relay Rivets. Use these original style rivets to attach the TCS relay to a new or existing wiring gutter.

Also available are the correct plastic plus used early in the 1970 Model year.

Send an email and ask for details.