Name that part.....

[BigCountryx]

I'm sure this is an easy one for most of you guys, but what in the world are these things? I've searched with no answer that I could find. This is on my 70. The thing on the firewall looks like some kind of relay, but for what? Best I can tell, there is a red wire that comes from inside the cab and goes to this relay thing. A black wire comes from the 2/3rd gear yoke on the trans (3 speed saginaw) and goes straight to that thing in the second pic. Then there's a blue and a green wire off of the relay thing, the blue is the other wire to the second pic and the green goes to the temp sensor on the therm housing, clear as mud huh. The piece in the second pic has a vac line from under the carb, it's mounted to the intake manifold and it's attached to some apparatus on the exhaust manifold.

[Andy4639]

Anti desialing stuff. Early goverment way to get the smog rules on the trucks.

[SS Tim]

That would be the transmission controlled spark system. Best bet is to take a look in section 6T of the factory service manual for a complete explanation of it's operation. If you don't have the manuals you can download some useable copies at the link in my signature.

[SS Tim]

Actually it has nothing to do with dieseling prevention. It is a spark advance inhibition system. There is also a technician's pocket service publication with some great details if you can find a copy, titled "NEW CHEVROLET EMISSION-CONTROL SYSTEMS" CC-69-12-10.

[TacBlade]

I just asked this same question a couple of months ago? I ended up thinking it has something to do with the emissions? Mine does not have any wired going to it, completely useless! Of course I have a 383 stroker in my truck now, so whatever it was, it is not needed. Here is the link to my question.

http://67-72chevytrucks.com/vboard/s...d.php?t=597270

[BigCountryx]

Cool, thanks. It appears mine isn't hooked up right anyway. The vac advance on my distributer is not hooked up to the solenoid, but directly to carb vac. Looks like I've got an engine bay cleanup project on the list. No reason this would hurt anything if it was relocated to the trash can.

[LockDoc]

Originally Posted by BigCountryx

Cool, thanks. It appears mine isn't hooked up right anyway. The vac advance on my distributer is not hooked up to the solenoid, but directly to carb vac. Looks like I've got an engine bay cleanup project on the list. No reason this would hurt anything if it was relocated to the trash can.

I wouldn't necessarily throw it away. Put it up on the parts board for a few bucks first and see what happens...

LockDoc

[SS Tim]

Originally Posted by LockDoc

I wouldn't necessarily throw it away. Put it up on the parts board for a few bucks first and see what happens...

LockDoc

Have to agree with Leon very strongly on this. Please don't just toss them. Offer them up on the parts board at a nominal price or even free for the ride. There are likely people looking for parts that they will not find at the bottom of your trash can.
Really this goes for anybody pulling nice stock bits during a modifed build.

[Steeveedee]

Transmission Controlled Spark, as SS Tim said.

It doesn't allow vacuum advance until the vehicle is in high gear. This also reduces NOX emissions. Yours also appears to have the thermal vacuum switch, which will not allow vacuum advance even in high gear unless the engine coolant is above a predetermined temperature. The engine warms up quicker with no vacuum advance, gets off the choke quicker, meaning higher efficiency.

If it works right, it doesn't really affect drivability.

[smoked68]

Thats the presidential advancement inhibitor, do not remove it, it does nothing but cost you more and more money, you will need to repace it every few months and all the data it spouts back at you is erronious at best and in reality it will just basically lie to you... but itll blame its failures on other parts..

[Sklptrljay]

Originally Posted by smoked68

Thats the presidential advancement inhibitor, do not remove it, it does nothing but cost you more and more money, you will need to repace it every few months and all the data it spouts back at you is erronious at best and in reality it will just basically lie to you... but itll blame its failures on other parts..

On the contrary, I'm all for removing the President(ial) advancement inhibitor. They claim to be American made, but turns out it's a foreign piece of junk. They have never actually worked, in fact it's really a drain on the entire vehicles system. Your truck would be a lot better off if you just stayed on a conservative path, and get rid of it.

[magwakeenercew2jh]

Originally Posted by Sklptrljay

On the contrary, I'm all for removing the President(ial) advancement inhibitor. They claim to be American made, but turns out it's a foreign piece of junk. They have never actually worked, in fact it's really a drain on the entire vehicles system. Your truck would be a lot better off if you just stayed on a conservative path, and get rid of it.

Well, they've had 'em on every model year for many years back. In fact, as much as they changed them out for one reason or another,
they all seem to be pretty much the same. If you read the box before you install them, the box almost always says that they add efficiency.
But when you put 'em under the hood, you find out it's just more added weight.

People that don't like the current part number usually don't always seem to remember the previous recalls and accidents that were caused by
the last group of broken OEM parts they sent us.

Of course, they are all really the same. No real purpose. And, all just add a lot of cost. And very little value. Like it or not, there's nothing
new with the latest castings.

[Sklptrljay]

Originally Posted by magwakeenercew2jh

Well, they've had 'em on every model year for many years back. In fact, as much as they changed them out for one reason or another,
they all seem to be pretty much the same. If you read the box before you install them, the box almost always says that they add efficiency.
But when you put 'em under the hood, you find out it's just more added weight.

People that don't like the current part number usually don't always seem to remember the previous recalls and accidents that were caused by
the last group of broken OEM parts they sent us.

Of course, they are all really the same. No real purpose. And, all just add a lot of cost. And very little value. Like it or not, there's nothing
new with the latest castings.

.....touche'

[BigCountryx]

Baaahahahahahaha

[JointTech]

hahahah. doesnt get political here very often.

[BigCountryx]

Well damn. U make me want to get it operable.

[quick60]

Depending on where he lives could removing it could affect its ability to pass state inspection? Just asking.

[Steeveedee]

Originally Posted by quick60

Depending on where he lives could removing it could affect its ability to pass state inspection? Just asking.

That depends on the state. In California, '75 and older vehicles are exempt from the biennial emissions inspection. So, you can pretty much do what you want, here.

Also, we don't have annual safety inspections like you see in the snow states. Probably should, some of the rolling wrecks I see around would be off the road.