Emissions part??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

crustysarge · 09-05-2004, 12:01 PM

This is located on the pass side on the intake. It has 3 wires and a vacuum source from the carb. I noticed it had a line with a screw so I put a vacuum cap on it.

What is this device? Where does the vacuum line go to? I also see what appears to be another nipple on the backside by the elect. plug.

Anybody have a 72 vacuum diagram they could share? Mine is a 350.

J.Lance · 09-05-2004, 02:33 PM

It is somewhat emissions related. It is a vacuum advance cutoff. It basically allows no timing advance until the motor has warmed up to operating temperature. The wiring would connect to one or two relays attached to the firewall either next to the fuse block or near the heater box. A 2nd temp. sending unit located on the passenger side of the block would trip the solenoid and open of vacuum to the distributor when it warmed up. If you look on the passenger side of teh block between the 6th and 8th cylinders, you should be able to see the sending unit or at least a plug where it once was.

Unless you're going back to stock, feel free to remove it along with the associated wiring. Your vacuum advance for the dist. should be hooked up to the carb where the vacuum solenoid is currently hooked to (ported vacuum). The wiring harness going up to the relays on the firewall and down to the sending unit is self contained and can be removed without cutting into any of the engine harness.

Hope this helps you out.

crustysarge · 09-06-2004, 09:43 AM

Thanks J. I would have never guessed that. PO installed an HEI and I was just about to check the ported advance and change wires as they are arcing.

jimfulco · 09-07-2004, 03:04 AM

TCS? Cuts off vacuum advance except in high gear.

72C203503ONTHETREE · 09-07-2004, 10:40 PM

Must be a California truck or something, my 72 was all original and it never had anything like that.

aesj2 · 09-07-2004, 11:05 PM

TCS. Had a 72 Blazer with that. Built and sold in Michigan.

JimKshortstep4x4 · 09-08-2004, 06:10 AM

The TCS system was not installed on the C 20 trucks and larger.

Jim

72C203503ONTHETREE · 09-08-2004, 11:05 AM

Ok, didnt think about that. Glad I don't have any of that crap to remove on my truck.

crustysarge · 09-10-2004, 05:13 PM

Pretty sure it is from Arkansas.

09-05-2004, 12:01 PM	#1
crustysarge Registered User Join Date: Mar 2004 Location: Aviano, Italy Posts: 221	Emissions part??? This is located on the pass side on the intake. It has 3 wires and a vacuum source from the carb. I noticed it had a line with a screw so I put a vacuum cap on it. What is this device? Where does the vacuum line go to? I also see what appears to be another nipple on the backside by the elect. plug. Anybody have a 72 vacuum diagram they could share? Mine is a 350. Attached Images

09-05-2004, 02:33 PM	#2
J.Lance Too many is never enough! Join Date: May 2003 Location: Idaho Falls, ID Posts: 455	advance cut off It is somewhat emissions related. It is a vacuum advance cutoff. It basically allows no timing advance until the motor has warmed up to operating temperature. The wiring would connect to one or two relays attached to the firewall either next to the fuse block or near the heater box. A 2nd temp. sending unit located on the passenger side of the block would trip the solenoid and open of vacuum to the distributor when it warmed up. If you look on the passenger side of teh block between the 6th and 8th cylinders, you should be able to see the sending unit or at least a plug where it once was. Unless you're going back to stock, feel free to remove it along with the associated wiring. Your vacuum advance for the dist. should be hooked up to the carb where the vacuum solenoid is currently hooked to (ported vacuum). The wiring harness going up to the relays on the firewall and down to the sending unit is self contained and can be removed without cutting into any of the engine harness. Hope this helps you out. __________________ Jason 1968 K10 SWB Fleetside 1971 K2500 GMC LWB 1968 K20 (later frame, donor body) 1972 C20 LWB parts truck 1993 K2500 Suburban, tow rig, 454, 4L80E NEW!! 18' Siem's car hauler 2004 Honda Odyssey (family man!)

09-07-2004, 10:40 PM	#5
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	Must be a California truck or something, my 72 was all original and it never had anything like that. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

09-08-2004, 11:05 AM	#8
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	Ok, didnt think about that. Glad I don't have any of that crap to remove on my truck. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

09-06-2004, 09:43 AM	#3
crustysarge Registered User Join Date: Mar 2004 Location: Aviano, Italy Posts: 221	Thanks J. I would have never guessed that. PO installed an HEI and I was just about to check the ported advance and change wires as they are arcing.

09-07-2004, 03:04 AM	#4
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	TCS? Cuts off vacuum advance except in high gear.

09-07-2004, 11:05 PM	#6
aesj2 Registered User Join Date: Feb 2002 Location: Ferndale, Michigan, USA Posts: 94	TCS. Had a 72 Blazer with that. Built and sold in Michigan.

09-08-2004, 06:10 AM	#7
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	The TCS system was not installed on the C 20 trucks and larger. Jim

09-10-2004, 05:13 PM	#9
crustysarge Registered User Join Date: Mar 2004 Location: Aviano, Italy Posts: 221	Pretty sure it is from Arkansas.



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