Vacume advance hookup - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Bilgewiper · 01-17-2003, 09:37 AM

On my totally stock '71 350 Quadrajet the vacume advance hose runs from the ft. of carb to this electrically controlled idle speed "thingy"........and then to the distributer. Can I just bypass this thing so I get advance during warm up or whenever that "thingy" says I can't? Whats not shown is a vacume hose comming off the top of the "thingy" which is hidden behind a hose in the picture........it goes to the charcoal canister.

Bilgewiper · 01-17-2003, 09:39 AM

the other end of "thingy"

Bilgewiper · 01-17-2003, 09:40 AM

Yes I know that hose has a crack in it........LOL!

Huck · 01-17-2003, 09:48 AM

You can run the vac hose direct from the carb to the dist vac advance. Believe that thingy may be for the A/C----Huck

Bilgewiper · 01-17-2003, 09:53 AM

Thanks, but I don't have a/c. Maybe something for Calif. smog? I don't know.

neonlarry · 01-17-2003, 02:14 PM

On mine there 2 vaccuum lines coming out of that piece. One goes to the the vaccuum advance, and the other goes to the back of the carb. Does anyone know what that line does? I have looked at diagrams of the q-jet, but I still can't figure it out.

lukecp · 01-17-2003, 04:22 PM

I'm also betting that is a California emissions thing. My original Arkansas truck didn't have anything like that when it still had the original 350 in it. It also didn't have a charcoal canister. If you don't have to get the truck inspected by the smog guys, i would be tempted to get rid of the charcoal canister. Maybe you could remove the "thingy" and see how it runs why you are at it........???

Bilgewiper · 01-17-2003, 06:26 PM

Thanks guys, I guess I'll just remove that "thingy" since in Ca. pre-1974 dosent have to get inspected anymore.........Yippee!

7T1BURB · 01-17-2003, 06:57 PM

The "thingy" is called the CEC (combination emission control) solenoid vacuum switch which is energized by grounding of the TCS switch at the transmission. "When the solenoid is in the non-energized position, vacuum to the distributor vacuum advance unit is shut off and the distributor is vented to atmosphere through a filter at the at the opposite end of the solenoid. Broken or disconnected electrical electrical connections resulting in failure of the solenoid to function will resuilt in no vacuum advance and no high gear deceleration throttle position."...per Service Manual pg. 6T-3.....have a "thingy" on our bone stock 307 and didn't know what is was or did..took me two months to find out what the "thingy" was and how it operated. If you look on the Driver's side of your transmission, you'll see the electrical lead going to the TCS.....if you need more info on the system operation, let me know and I'll send you the info.......hope this helps. I don't know about "disconnecting"/"bypassing" this solenoid as our engine has not been fired-up yet after rebuild... not a California peculiar system as our Burb was initially a Pennsyvlavia purchased vehicle..

Bilgewiper · 01-17-2003, 07:22 PM

Thanks...........that sheds light on the "Thingy". I like "thingy " better than CEC.

1badz · 01-17-2003, 11:57 PM

7t1burb: I was wondering if you could by pass the vacuum advance altogether and turn up the initial timing from say 8 to around 14 degrees thus causing faster acceleration.which would be caused by no loss of vacuum from the carb under fast and hard acceleration, since there is a slight loss of vacuum just for a split second, and you could then put a cap on the vacuum port on the dist. and the carb.Just wondering if that would help.

Bilgewiper · 01-27-2003, 05:51 PM

Finally got around to tuneing this thing up and bypassing that CEC (thanks 7T1BURB). Boy did that wake this thing up. I doubt it ever got vacume advance. Thanks again

01-17-2003, 09:37 AM	#1
Bilgewiper Registered User Join Date: Dec 2002 Location: Citrus Heights Ca. Posts: 186	Vacume advance hookup On my totally stock '71 350 Quadrajet the vacume advance hose runs from the ft. of carb to this electrically controlled idle speed "thingy"........and then to the distributer. Can I just bypass this thing so I get advance during warm up or whenever that "thingy" says I can't? Whats not shown is a vacume hose comming off the top of the "thingy" which is hidden behind a hose in the picture........it goes to the charcoal canister. Attached Images __________________ Ethan '71 C-10 LWB Cheyenne 85K miles. "Time spent Boating is NOT deducted from ones lifespan".

01-17-2003, 09:39 AM	#2
Bilgewiper Registered User Join Date: Dec 2002 Location: Citrus Heights Ca. Posts: 186	the other end of "thingy" Attached Images __________________ Ethan '71 C-10 LWB Cheyenne 85K miles. "Time spent Boating is NOT deducted from ones lifespan".

01-17-2003, 09:40 AM	#3
Bilgewiper Registered User Join Date: Dec 2002 Location: Citrus Heights Ca. Posts: 186	Yes I know that hose has a crack in it........LOL! __________________ Ethan '71 C-10 LWB Cheyenne 85K miles. "Time spent Boating is NOT deducted from ones lifespan".

01-17-2003, 09:53 AM	#5
Bilgewiper Registered User Join Date: Dec 2002 Location: Citrus Heights Ca. Posts: 186	Thanks, but I don't have a/c. Maybe something for Calif. smog? I don't know. __________________ Ethan '71 C-10 LWB Cheyenne 85K miles. "Time spent Boating is NOT deducted from ones lifespan".

01-17-2003, 02:14 PM	#6
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,746	On mine there 2 vaccuum lines coming out of that piece. One goes to the the vaccuum advance, and the other goes to the back of the carb. Does anyone know what that line does? I have looked at diagrams of the q-jet, but I still can't figure it out. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

01-17-2003, 09:48 AM	#4
Huck Senior Member Join Date: Jun 2001 Location: Shelbyville, KY Posts: 3,269	You can run the vac hose direct from the carb to the dist vac advance. Believe that thingy may be for the A/C----Huck

01-17-2003, 04:22 PM	#7
lukecp Formerly yellow72custom Join Date: May 2001 Location: Austin, TX Posts: 7,531	I'm also betting that is a California emissions thing. My original Arkansas truck didn't have anything like that when it still had the original 350 in it. It also didn't have a charcoal canister. If you don't have to get the truck inspected by the smog guys, i would be tempted to get rid of the charcoal canister. Maybe you could remove the "thingy" and see how it runs why you are at it........??? __________________ '72 Chevy C10 Mild 350/TH350/3.07. Ochre/White. Old high school ride. '70 GMC C2500 '62 327 4bbl/SM465/4.56-geared Dana 60. White/White. Project or parts truck. '97 Saturn SL DD. 1.9/5-speed. 40+ highway mpg

01-17-2003, 06:26 PM	#8
Bilgewiper Registered User Join Date: Dec 2002 Location: Citrus Heights Ca. Posts: 186	Thanks guys, I guess I'll just remove that "thingy" since in Ca. pre-1974 dosent have to get inspected anymore.........Yippee! __________________ Ethan '71 C-10 LWB Cheyenne 85K miles. "Time spent Boating is NOT deducted from ones lifespan".

01-17-2003, 06:57 PM	#9
7T1BURB Registered User Join Date: Aug 2002 Location: Newport News, VA Posts: 190	The "thingy" is called the CEC (combination emission control) solenoid vacuum switch which is energized by grounding of the TCS switch at the transmission. "When the solenoid is in the non-energized position, vacuum to the distributor vacuum advance unit is shut off and the distributor is vented to atmosphere through a filter at the at the opposite end of the solenoid. Broken or disconnected electrical electrical connections resulting in failure of the solenoid to function will resuilt in no vacuum advance and no high gear deceleration throttle position."...per Service Manual pg. 6T-3.....have a "thingy" on our bone stock 307 and didn't know what is was or did..took me two months to find out what the "thingy" was and how it operated. If you look on the Driver's side of your transmission, you'll see the electrical lead going to the TCS.....if you need more info on the system operation, let me know and I'll send you the info.......hope this helps. I don't know about "disconnecting"/"bypassing" this solenoid as our engine has not been fired-up yet after rebuild... not a California peculiar system as our Burb was initially a Pennsyvlavia purchased vehicle.. Last edited by 7T1BURB; 01-17-2003 at 07:01 PM.

01-17-2003, 07:22 PM	#10
Bilgewiper Registered User Join Date: Dec 2002 Location: Citrus Heights Ca. Posts: 186	Thanks...........that sheds light on the "Thingy". I like "thingy " better than CEC. __________________ Ethan '71 C-10 LWB Cheyenne 85K miles. "Time spent Boating is NOT deducted from ones lifespan".

01-17-2003, 11:57 PM	#11
1badz Registered User Join Date: Jan 2003 Location: S.D. Posts: 36	7t1burb: I was wondering if you could by pass the vacuum advance altogether and turn up the initial timing from say 8 to around 14 degrees thus causing faster acceleration.which would be caused by no loss of vacuum from the carb under fast and hard acceleration, since there is a slight loss of vacuum just for a split second, and you could then put a cap on the vacuum port on the dist. and the carb.Just wondering if that would help.

01-27-2003, 05:51 PM	#12
Bilgewiper Registered User Join Date: Dec 2002 Location: Citrus Heights Ca. Posts: 186	Finally got around to tuneing this thing up and bypassing that CEC (thanks 7T1BURB). Boy did that wake this thing up. I doubt it ever got vacume advance. Thanks again __________________ Ethan '71 C-10 LWB Cheyenne 85K miles. "Time spent Boating is NOT deducted from ones lifespan".



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