'73 Early Emissions Part Nos. Wanted
 

Any experts that can help me with an early production '73 Emissions set-up?

Trying to learn what I'm missing what parts are still available.

Not sure I have correct p/ns.

Start with the TCS Switch mounted to the trans.

I show p/n 490751 or Delco D6400.

Is this the correct p/n?

Are these available anywhere new aftermarket, NOS, or used (working or not)?
Lots more help needed but start with this part first.

Thanks.

Early production as in pre EGR fiasco?


:confused:

John, yes. Built in January '73 so before all the EPA required EGR changes.

Hello John, if you PM me your email address, I can send you some good articles that go over the two smog systems. If you can determine what you need let me know as well as I have a few of the early components.

I thought I had some numbers, but just could find the tech bulletins. (no numbers)


Rocky had an article on the differences in HPP, I believe.
(2005 or so)


:)

Thanks for the replies.

You guys might already realize this, but I forgot to mention that my original TA engine was a WT code 455 with Unitized Distributor option and 4 spd.

John, I've read Rocky's older article but did not see any p/ns mentioned. I also have the Pontiac Enthusiast issues with the articles written by Peter Serio although I have packed them away in storage so would be difficult to access them at the moment. Don't think p/ns are mentioned in them either.

SD73, a PM has been sent.

Scott, do you know if the Corvette TCS Switch interchanges? The late '73 Pontiac TCS was changed to p/n 494366 which crosses to Delco D6401. Unclear to me what changed. But makes me think each TCS Switch was functionally different.

Moving to another question, where do the Thermal Override Switch and the Thermal Delay Switch get installed?

John, article sent. I think it's the same one you have packed away. It should have many of the answers your looking for. As far as the thermo switches, there are two that are screwed into the front of the intake manifold with vacuum ports. and another switch at the back of the drivers side head that affects the distributor advance when an overheat temp is reached.

HFR thanks for that link!

I don't suppose you still have that 490751 TCS Switch and willing to part with it?

I'm not up to speed on the late '73 system.

The early TCS Switch did install at the 1-2 Shft Lever boss and was only open in 1st gear, closed in all other gears.

The late TCS Switch was carried over for use in '74.

The redesign required PMD to separate the TCS and EGR circuits. The early year system was designed so that they were tied together and if the EGR Solenoid was energized, then the EGR was closed (no EGR).

Let me know about that TCS Switch. Thanks!