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

BCOWANWHEELS · 09-08-2009, 11:27 PM

Where is the best place on a 350 to hookup a vac gauge. also what kind of line did the factory use for this hookup.
thanks again
bob

**leddzepp** · 09-08-2009, 11:30 PM

I have mine hooked up to the intake manifold. I believe the factory used a metal line (like the oil pressure gauge).

vectorit · 09-08-2009, 11:34 PM

Vu Ja De... I asked this question last year I think.

This is what I ended up doing.

I picked up a new intake manifold vacuum connector at the resto shop that had a provision for a rubber hose next to the brake booster connection, and then just ran a thick walled rubber hose from that manifold connection through a hole in the fire wall. I got a brass fitting at Lowe's for the back of the gauge, and the rubber hose slipped onto it. Before I connected it I put some grafite on the connections to ensure a good seal.

I suspect this is not how the factory did it, but it works just fine for me these days with out any issues.

BCOWANWHEELS · 09-08-2009, 11:41 PM

where is the best place on the manifold ? under the carb or in a intake runner ? i,am going to use a metal line or at least a braided stainless-nylon line. rubber will collapse under full vacume i think

Longhorn Man · 09-09-2009, 06:20 AM

it doesn't matter.

BCOWANWHEELS · 09-09-2009, 05:01 PM

Thanks andy

long69 · 09-09-2009, 06:07 PM

i connect mine to the proper port on the carb.

Longhorn Man · 09-09-2009, 10:52 PM

can you call it a "proper port"... when it's not a "proper" guage?
There's no right or wrong way, as long as it gets the vacuum signal from under the throttle plates, then it will get the correct reading.
Like I said, it doesn't matter.

long69 · 09-10-2009, 04:04 AM

well there are two different vacuums in most every carb. i do not no the correct name for each one. i choose the one that gives me the reading i'm looking for (manifold vacuum ).choose the wrong one you'll get next to zero at idle, punch it and it will shoot up, that one is not the proper one for a gauge. the suggestions were to connect to the intake itself, mine was to connect to the carb hook to the wrong port on the carb and you get readings that are not what you expect.

Longhorn Man · 09-10-2009, 06:16 AM

yep, full manifold, and ported. Prted is above the throttle plates on the carb.
As, as long as it is hooked up below the throttle plates...

BCOWANWHEELS · 09-10-2009, 02:16 PM

could some tell me which one on the q-jet carb to hook it to ? i have a 72 ,350, auto.

09-08-2009, 11:27 PM	#1
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Vacume gauge hookup question Where is the best place on a 350 to hookup a vac gauge. also what kind of line did the factory use for this hookup. thanks again bob __________________ I BELIEVE IN JOHN 3:16

09-08-2009, 11:30 PM	#2
leddzepp Moderator Join Date: May 2007 Location: Southern Cal Posts: 20,001	Re: Vacume gauge hookup question I have mine hooked up to the intake manifold. I believe the factory used a metal line (like the oil pressure gauge). __________________ 1972 C/10 Cheyenne Super SWB. Restored, loaded, slammed. 1968 C/10 50th Anniversary LWB. Unrestored, stock, daily driver/work truck. RIP ElJay RIP 67ChevyRedneck RIP Grumpy Old Man

09-08-2009, 11:34 PM	#3
vectorit What? Join Date: Jun 2007 Location: Southern California Posts: 7,617	Re: Vacume gauge hookup question Vu Ja De... I asked this question last year I think. This is what I ended up doing. I picked up a new intake manifold vacuum connector at the resto shop that had a provision for a rubber hose next to the brake booster connection, and then just ran a thick walled rubber hose from that manifold connection through a hole in the fire wall. I got a brass fitting at Lowe's for the back of the gauge, and the rubber hose slipped onto it. Before I connected it I put some grafite on the connections to ensure a good seal. I suspect this is not how the factory did it, but it works just fine for me these days with out any issues. __________________ Chris 1968 K20 Suburban 1972 K10 LWB PU

09-08-2009, 11:41 PM	#4
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Re: Vacume gauge hookup question where is the best place on the manifold ? under the carb or in a intake runner ? i,am going to use a metal line or at least a braided stainless-nylon line. rubber will collapse under full vacume i think __________________ I BELIEVE IN JOHN 3:16

09-09-2009, 06:20 AM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Vacume gauge hookup question it doesn't matter.

09-09-2009, 05:01 PM	#6
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Re: Vacume gauge hookup question Thanks andy __________________ I BELIEVE IN JOHN 3:16

09-09-2009, 06:07 PM	#7
long69 Registered User Join Date: Oct 2006 Location: lost angeles Posts: 159	Re: Vacume gauge hookup question i connect mine to the proper port on the carb.

09-09-2009, 10:52 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Vacume gauge hookup question can you call it a "proper port"... when it's not a "proper" guage? There's no right or wrong way, as long as it gets the vacuum signal from under the throttle plates, then it will get the correct reading. Like I said, it doesn't matter.

09-10-2009, 04:04 AM	#9
long69 Registered User Join Date: Oct 2006 Location: lost angeles Posts: 159	Re: Vacume gauge hookup question well there are two different vacuums in most every carb. i do not no the correct name for each one. i choose the one that gives me the reading i'm looking for (manifold vacuum ).choose the wrong one you'll get next to zero at idle, punch it and it will shoot up, that one is not the proper one for a gauge. the suggestions were to connect to the intake itself, mine was to connect to the carb hook to the wrong port on the carb and you get readings that are not what you expect. Last edited by long69; 09-10-2009 at 04:10 AM.

09-10-2009, 06:16 AM	#10
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Vacume gauge hookup question yep, full manifold, and ported. Prted is above the throttle plates on the carb. As, as long as it is hooked up below the throttle plates...

09-10-2009, 02:16 PM	#11
BCOWANWHEELS Registered User Join Date: Nov 2006 Location: KINGSPORT,TN. Posts: 3,035	Re: Vacume gauge hookup question could some tell me which one on the q-jet carb to hook it to ? i have a 72 ,350, auto. __________________ I BELIEVE IN JOHN 3:16

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