Quadrajet question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**kna4977** · 10-19-2024, 01:58 PM

Have a quadrajet on a 72. The front vacuum port is plugged which I understand to be normal. It has one on the passenger side near the choke setup that is open and not capped. What is this supposed to go to or should it be capped? Here’s a pic.

howzzzit · 10-19-2024, 02:16 PM

It's called a diverter port. I have no idea what it would be used for, but I think it has vacuum at idle. Mine is capped.

geezer#99 · 10-19-2024, 02:20 PM

Charcoal canister full time manifold vacuum port.

**1970cstblazer** · 10-19-2024, 02:29 PM

The one on the side of the carb is a manifold vacuum source for the air cleaner Thermac snorkel valve.

If you are looking for the utmost correct look, the TCS emission control system is missing, and it appears the lines to the charcoal canister are gone.

**kna4977** · 10-19-2024, 06:46 PM

Quote:

Originally Posted by 1970cstblazer

The one on the side of the carb is a manifold vacuum source for the air cleaner Thermac snorkel valve.

If you are looking for the utmost correct look, the TCS emission control system is missing, and it appears the lines to the charcoal canister are gone.

Not sure why anyone would want a TCS system and I understand why people would remove them and throw them away. They seem like a PITA. Bet a complete working system is super hard to find today.

What did it all look like originally and where did the charcoal canister mount? Did all the 72s come with them?

For now I'm going to cap it off.

howzzzit · 10-20-2024, 01:32 AM

Quote:

Originally Posted by kna4977

Not sure why anyone would want a TCS system and I understand why people would remove them and throw them away. They seem like a PITA. Bet a complete working system is super hard to find today.

What did it all look like originally and where did the charcoal canister mount? Did all the 72s come with them?

For now I'm going to cap it off.

Canister next to and below the battery. They were an answer to non-vented fuel tanks. The charcoal absorbed the fuel vapors instead of venting out the cap. My 72 is a C10 and I may be wrong, but I believe only 1/2 tons had the canister and smog setup that year. Someone will know for sure.

**1970cstblazer** · 10-20-2024, 07:20 AM

Quote:

Originally Posted by kna4977

Not sure why anyone would want a TCS system and I understand why people would remove them and throw them away. They seem like a PITA. Bet a complete working system is super hard to find today.

What did it all look like originally and where did the charcoal canister mount? Did all the 72s come with them?

For now I'm going to cap it off.

You do realize that you can have the solenoid present, and all hooked up, and vacuum can pass through it as long as it is not electrically energized...

**1970cstblazer** · 10-20-2024, 09:39 AM

geezer#99 · 10-20-2024, 12:29 PM

Quote:

Originally Posted by 1970cstblazer

You do realize that you can have the solenoid present, and all hooked up, and vacuum can pass through it as long as it is not electrically energized...

Actually you get no vacuum thru it until you’re in high gear.

**kna4977** · 10-20-2024, 09:08 PM

Quote:

Originally Posted by 1970cstblazer

You do realize that you can have the solenoid present, and all hooked up, and vacuum can pass through it as long as it is not electrically energized...

I do now. I would like a completely factory stock appearing but non-functional setup, but not sure what all would be needed. Components underneath the truck probably don't matter. Would just need the pieces for the system that are visible underhood.

howzzzit · 10-19-2024, 04:22 PM

Quote:

Originally Posted by geezer#99

Charcoal canister full time manifold vacuum port.

My quadrajet has a canister purge port on the front. It is ported vacuum. Anytime engine is off idle it activates the switch at the canister which in turns allows the canister pcv port to open and dump the fumes into the pcv port at the carb through a tee. I changed my old canister and added an external switch. New ones don't have it built in and it works great. No more gas fumes.

geezer#99 · 10-20-2024, 09:37 PM

Keep it functional and just hook the wire on the trans to a good ground.

geezer#99 · 10-21-2024, 09:53 AM

Lookee there!
A solenoid deep in the shadow with no indication of how the vac hoses are connected to it.

**1970cstblazer** · 10-21-2024, 10:45 AM

That's all you are getting. It's very plain to see from where I am sitting.

geezer#99 · 10-21-2024, 12:26 PM

Typical!

**1970cstblazer** · 10-21-2024, 12:41 PM

This message is hidden because geezer#99 is on your ignore list.

geezer#99 · 10-21-2024, 12:43 PM

C’mon!
You can do better than that!

**kna4977** · 10-21-2024, 01:31 PM

So all I would need is said solenoid the mounting bracket bolt and a couple of vacuum lines?

**Steeveedee** · 10-21-2024, 01:57 PM

If you don't have the repair manual for your truck, you can get one here for free download. I don't have this system on my truck, since it's a 3/4T. But this manual will show it.
https://67-72chevytrucks.com/vboard/...ghlight=hatzie

10-19-2024, 01:58 PM	#1
kna4977 Senior Member Join Date: Jul 2006 Location: Midlothian TX Posts: 499	Quadrajet question Have a quadrajet on a 72. The front vacuum port is plugged which I understand to be normal. It has one on the passenger side near the choke setup that is open and not capped. What is this supposed to go to or should it be capped? Here’s a pic. Attached Images

10-19-2024, 02:16 PM	#2
howzzzit Registered User Join Date: Dec 2005 Location: Kalifornia Posts: 355	Re: Quadrajet question It's called a diverter port. I have no idea what it would be used for, but I think it has vacuum at idle. Mine is capped.

10-19-2024, 02:20 PM	#3
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,749	Re: Quadrajet question Charcoal canister full time manifold vacuum port.

10-19-2024, 02:29 PM	#4
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,894	Re: Quadrajet question The one on the side of the carb is a manifold vacuum source for the air cleaner Thermac snorkel valve. If you are looking for the utmost correct look, the TCS emission control system is missing, and it appears the lines to the charcoal canister are gone. __________________ 1970 K/5 Blazer CST 4WD, TOTM winner December 2024! Medium Bronze, 93k ACT. miles, 350, 4 speed, rear positraction, 16.5" x 8.25" HD wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration finally getting close to completion.. 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 45k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 62k miles, 3.6, 8L45, 3.23 LS, 18" wheels

10-20-2024, 09:39 AM	#8
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,894	Re: Quadrajet question __________________ 1970 K/5 Blazer CST 4WD, TOTM winner December 2024! Medium Bronze, 93k ACT. miles, 350, 4 speed, rear positraction, 16.5" x 8.25" HD wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration finally getting close to completion.. 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 45k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 62k miles, 3.6, 8L45, 3.23 LS, 18" wheels

10-20-2024, 09:37 PM	#12
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,749	Re: Quadrajet question Keep it functional and just hook the wire on the trans to a good ground.

10-21-2024, 09:53 AM	#13
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,749	Re: Quadrajet question Lookee there! A solenoid deep in the shadow with no indication of how the vac hoses are connected to it.

10-21-2024, 10:45 AM	#14
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,894	Re: Quadrajet question That's all you are getting. It's very plain to see from where I am sitting. __________________ 1970 K/5 Blazer CST 4WD, TOTM winner December 2024! Medium Bronze, 93k ACT. miles, 350, 4 speed, rear positraction, 16.5" x 8.25" HD wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration finally getting close to completion.. 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 45k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 62k miles, 3.6, 8L45, 3.23 LS, 18" wheels

10-21-2024, 12:26 PM	#15
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,749	Re: Quadrajet question Typical!

10-21-2024, 12:41 PM	#16
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,894	Re: Quadrajet question This message is hidden because geezer#99 is on your ignore list. __________________ 1970 K/5 Blazer CST 4WD, TOTM winner December 2024! Medium Bronze, 93k ACT. miles, 350, 4 speed, rear positraction, 16.5" x 8.25" HD wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration finally getting close to completion.. 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 45k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 62k miles, 3.6, 8L45, 3.23 LS, 18" wheels

10-21-2024, 12:43 PM	#17
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,749	Re: Quadrajet question C’mon! You can do better than that!

10-21-2024, 01:31 PM	#18
kna4977 Senior Member Join Date: Jul 2006 Location: Midlothian TX Posts: 499	Re: Quadrajet question So all I would need is said solenoid the mounting bracket bolt and a couple of vacuum lines?

10-21-2024, 01:57 PM	#19
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,747	Re: Quadrajet question If you don't have the repair manual for your truck, you can get one here for free download. I don't have this system on my truck, since it's a 3/4T. But this manual will show it. https://67-72chevytrucks.com/vboard/...ghlight=hatzie __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA



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