Vacuum Cluster - The 1947 - Present Chevrolet & GMC Truck Message Board Network

lts70 · 04-03-2008, 07:03 PM

I have a friend that is giving me a factory vacuum gauge out of C-50 truck of his. My question is can I just take the vac gauge or do I need to grab the entire cluster? Can I just polish off the lines of my normal cluster where the vac gauge goes? If it had a tach there would be no question. I know they did not come stock on C-10's but I like the idea of haveing no empty spaces in my gauge cluster.

**Gary 70 Jimmy** · 04-03-2008, 07:36 PM

You need the the hole cluster, you need the lens that says vaccuum on it and the backing plate so you can see the gauge.

lts70 · 04-03-2008, 09:42 PM

Thanks Gary that makes sense, I will just swap him my cluster for his.

Where is the best place to hook up a vacuum gauge on a C-10?

What are some advanages of having a vacuum gauge?

Mint68 · 04-04-2008, 02:48 AM

I thought the fuel guages were different in some. Not sure, but you may want to figure that out before just swaping the whole cluster.

ed2552 · 04-04-2008, 02:52 AM

Doesn't the C-50 have a tach? i was told they all did b/c they all had manual trannys

lts70 · 04-04-2008, 03:20 AM

Does anyone know how to check if the gas gauge is correct?

Maybe it is a C-30 because it does not have a tachometer. It was a wrecking truck before he got it for around the farm.

Where is the best place to hook up a vacuum gauge on a C-10?
What are some advantages of having a vacuum gauge in a smaller truck? I think the big trucks had them for there brake systems but wouldn't it be convenient on a smaller truck to see how the engine is running?

**oldgold70c10** · 04-04-2008, 03:28 AM

My C-50 doesn't have a tach or vacuum gauge, they were optional. Gas guage should be the same, since it uses the same tank as the c-10. The vacuum guage is very nice for tuning, seeing how the engine is running, and driving to get best MPG. I have a vacuum guage mounted in front of the empty cluster hole and I am using a manifold vacuum port.

wibilly · 04-04-2008, 05:19 AM

keep your bezel if you trade. they are different around the stearing colume

**1970cstblazer** · 04-04-2008, 06:30 AM

Quote:

Originally Posted by lts70

Does anyone know how to check if the gas gauge is correct?

Maybe it is a C-30 because it does not have a tachometer. It was a wrecking truck before he got it for around the farm.

Where is the best place to hook up a vacuum gauge on a C-10?
What are some advantages of having a vacuum gauge in a smaller truck? I think the big trucks had them for there brake systems but wouldn't it be convenient on a smaller truck to see how the engine is running?

The big truck fuel gauge is close, but the red warning lamps do not say "BRAKE" and "TEMP". I believe they say "TANDEM LOCK" and "OVERSPEED".

Just hook the vacuum gauge to a manifold vacuum source, not a ported vacuum source.

lts70 · 04-04-2008, 06:51 AM

Thanks willbilly for reminding me about the bezel being different around the steering column. I would have forgotten that one for sure.

How can you know by looking at the vacuum gauge that you are driving to get best MPG? Is there a sweet spot between 0 and 30 on the dial that you would want to cruise at? What are some of the ways you can use a vacuum for tuning and seeing how the engine is running?

What do "TANDEM LOCK" and "OVERSPEED" indicate?

How can you tell the difference between a manifold vacuum source, not a ported vacuum source?

Thanks for all of the info guys. Every time I spend a few hours with you guys I learn a ton. I can’t get enough of this stuff. It seems like for every answer I get I have five more questions because of my new knowledge. Let me know if I start driving you guys insane with my never ending questions.

**WorkinLonghorn** · 04-04-2008, 08:06 AM

Ported Vac is out of the carb,manifold vac is right off the mani. Engine can be monitored somewhat with a vac reading.Get a shop manual,they tell you all about the differnt readings but basically the higher the better and it should be steady,not jerking.
Some cars used to have a vac gauge "mileage meter".Higher vac=better mileage,but really it's about the same as "light foot=better mileage.

lts70 · 04-04-2008, 08:28 AM

I have an Edelbrock AirGap. Will this port in the picture work?

Does any one know what "TANDEM LOCK" and "OVERSPEED" lights in a C-50 fuel gauge would indicate?

**WorkinLonghorn** · 04-04-2008, 09:12 AM

Yeah,that will work,but you will need a tee on there for any other vacuum needs,ie. Trans.modulator,vac-assist brakes etc.I'm not familiar with that mani but I'm sure it came with a diagram of some sort for the hook-ups (?).

**1970cstblazer** · 04-04-2008, 04:00 PM

Quote:

Originally Posted by lts70

I have an Edelbrock AirGap. Will this port in the picture work?

Does any one know what "TANDEM LOCK" and "OVERSPEED" lights in a C-50 fuel gauge would indicate?

That port would work fine.

The tandem lock was used in the few trucks with tandem axles. The light would come on when the axles were locked together.

The overspeed light would come on if the engine was being operated in a danger zone, at or above the goverened speed.

lts70 · 04-04-2008, 07:21 PM

The red warning lamps that say "BRAKE" and "TEMP" in my truck have never worked. Is there a common reason for this? I would really like the brake light to work as I leave the parking brake on every now and again on accident. It would be nice to have the light let me know they are still on and not the smell of burning brakes.

**WorkinLonghorn** · 04-04-2008, 11:12 PM

As far as I know the brake warning light goes on when the pressure switch under the master cylinder detects a pressure imbalance,front to back,on a dual system such as your '70 would have. This lets you know is there is a leak in either the front,or back brakes. It wont go on if you forget the parking brake.(Mine has never worked,needs a new light bulb). I think the light should go on when you twist the key to start up,if not replace it. Same for the temp light,although I have a gauge so not sure on this one.

**oldgold70c10** · 04-05-2008, 02:21 AM

The temp light is not hooked up on a guage cluster. However, their is an empty contact spot in the cluster plug if you wanted to hook it up to a second "idiot light" temp sender to come on if the engine got too hot.

lts70 · 04-08-2008, 07:57 PM

Well I got the Vacuum gauge this week end. It looks like someone was pulling on the engine bay side of the vacuum line and may have tweaked the gauge slightly. When I started to bend it straight I noticed that it was moving needle so I stopped.

So now I have yet another stupid question for you guys. Where does the needle rest on a vacuum gauge when it is unhooked? I would think at Zero but in the picture above it is at 25. I am hoping I can bend the back of the gauge back until it reads what it should and hopefully it will work from there. Anyone have any experience with this?

On another note the truck I got the gauge out of had what looked like a factory non-shifter tilt column (it had the short shaft at the bottom of the column not the longer van looking shaft). Did they make non-automatic tilts for these trucks? What would be a fair price to give him for it?

jay_shy · 04-08-2008, 09:59 PM

They did make floor shift tilts but they are few and far between. If I am correct,and if its tight you could probably get 400.00 for it.

Jason

pritch · 04-09-2008, 04:18 AM

Hey Lehi! I don't have anything to add, just wanted to say hi from Coalville!

ETsC10 · 04-09-2008, 05:38 AM

Quote:

Originally Posted by WorkinLonghorn

Ported Vac is out of the carb,manifold vac is right off the mani. Engine can be monitored somewhat with a vac reading.Get a shop manual,they tell you all about the differnt readings but basically the higher the better and it should be steady,not jerking.
Some cars used to have a vac gauge "mileage meter".Higher vac=better mileage,but really it's about the same as "light foot=better mileage.

yup, 1962 vintage...

**'68OrangeSunshine** · 04-09-2008, 02:21 PM

Vacuum gauges are calibrated in Inches of Mercury. Expressed as X"Hg. For example, when my engine idles at operating temps, it indicates 17"Hg. Cruising It shows 8" to 12" Hg. Step on it going up a hill and 5'' will drop to 0" Hg. Engine brake down a hill and it will jump to 20" Hg. If the needle bounces at 15 - 17" Hg at idle you may have a sticky valve. Also real handy for dialing in the carb.
Check out this site [if it's still up]:
http://www.centuryperformance.com/va...Valve%20Timing.

lts70 · 04-09-2008, 08:29 PM

Does anyone know if a vacuum gauge needle rests at zero when the motor is off? I think it should but I want to make sure before I start bending on the internals to get it there. Right now it is in the middle at 15 and in the picture above it is at 25. I think it got tweaked when some one took the brake system off the truck and the vacuum gauge got pulled out a bit with the vacuum line before they realized to unhook it.

lts70 · 04-10-2008, 07:08 AM

Found some pictures that answered my question. Zero it is. Does anyone re-pop the speed warning gauge like the one in the first picture?

04-03-2008, 07:03 PM	#1
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Vacuum Cluster I have a friend that is giving me a factory vacuum gauge out of C-50 truck of his. My question is can I just take the vac gauge or do I need to grab the entire cluster? Can I just polish off the lines of my normal cluster where the vac gauge goes? If it had a tach there would be no question. I know they did not come stock on C-10's but I like the idea of haveing no empty spaces in my gauge cluster. __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance. Last edited by lts70; 04-03-2008 at 09:40 PM.

04-03-2008, 07:36 PM	#2
Gary 70 Jimmy Senior Member Join Date: Jan 2002 Location: Burghill, Ohio 44404 Posts: 3,401	Re: Vacuum Cluster You need the the hole cluster, you need the lens that says vaccuum on it and the backing plate so you can see the gauge.

04-03-2008, 09:42 PM	#3
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Re: Vacuum Cluster Thanks Gary that makes sense, I will just swap him my cluster for his. Where is the best place to hook up a vacuum gauge on a C-10? What are some advanages of having a vacuum gauge? __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance.

04-04-2008, 02:48 AM	#4
Mint68 Registered User Join Date: Nov 2004 Location: Nebraska Posts: 762	Re: Vacuum Cluster I thought the fuel guages were different in some. Not sure, but you may want to figure that out before just swaping the whole cluster.

04-04-2008, 02:52 AM	#5
ed2552 Registered User Join Date: Jan 2007 Location: Charles City IA Posts: 1,626	Re: Vacuum Cluster Doesn't the C-50 have a tach? i was told they all did b/c they all had manual trannys __________________ '67 C20, Under the Knife!, LWB, Eaton HO-52, Rear Coil Springs 72' GMC C2500, 350, TH400(?), Dana 60 '67 K10 4-spd., 305, SM465, Dana 44, 12 Bolt, RUST! '65 C60 292, 4 spd, 2 spd Rearend, 15' Grain Box, MINT! 09 Yukon Denali 82k Miles 6.2L/6A

04-04-2008, 03:20 AM	#6
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Re: Vacuum Cluster Does anyone know how to check if the gas gauge is correct? Maybe it is a C-30 because it does not have a tachometer. It was a wrecking truck before he got it for around the farm. Where is the best place to hook up a vacuum gauge on a C-10? What are some advantages of having a vacuum gauge in a smaller truck? I think the big trucks had them for there brake systems but wouldn't it be convenient on a smaller truck to see how the engine is running? __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance.

04-04-2008, 03:28 AM	#7
oldgold70c10 Who's got steelies? Join Date: Feb 2006 Location: Morrison, Oklahoma Posts: 1,025	Re: Vacuum Cluster My C-50 doesn't have a tach or vacuum gauge, they were optional. Gas guage should be the same, since it uses the same tank as the c-10. The vacuum guage is very nice for tuning, seeing how the engine is running, and driving to get best MPG. I have a vacuum guage mounted in front of the empty cluster hole and I am using a manifold vacuum port. __________________ 1969 C10 LWB W/ 250 I6 & 3spd 1970 C10 with '67 small window cab, 68 front end, blue; 305/TH350, 3.08 limited slip rear end, manual brakes, power steering; & 4-wheel drums-My daily driver. 1975 Chevelle Malibu Classic Coupe 350/th350 mint green 1970 C20 Suburban 350/700R4 4.10 gearing green & white 1978 Big 10 Silverado 350/th350, working ac, 2 tone blue-My summer daily driver 1983 GMC 1500 Sierra 305/SM465 2.73 rear end How to add a trip odometer to your 67-72 stock speedometer How to rebuild your Q-Jet My Truck Page My Youtube Channel

04-04-2008, 05:19 AM	#8
wibilly Senior Member Join Date: Nov 2005 Location: northwestern wi Posts: 2,111	Re: Vacuum Cluster keep your bezel if you trade. they are different around the stearing colume __________________ common sense isn't so common anymore

04-04-2008, 06:51 AM	#10
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Re: Vacuum Cluster Thanks willbilly for reminding me about the bezel being different around the steering column. I would have forgotten that one for sure. How can you know by looking at the vacuum gauge that you are driving to get best MPG? Is there a sweet spot between 0 and 30 on the dial that you would want to cruise at? What are some of the ways you can use a vacuum for tuning and seeing how the engine is running? What do "TANDEM LOCK" and "OVERSPEED" indicate? How can you tell the difference between a manifold vacuum source, not a ported vacuum source? Thanks for all of the info guys. Every time I spend a few hours with you guys I learn a ton. I can’t get enough of this stuff. It seems like for every answer I get I have five more questions because of my new knowledge. Let me know if I start driving you guys insane with my never ending questions. Attached Images __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance.

04-04-2008, 08:06 AM	#11
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,886	Re: Vacuum Cluster Ported Vac is out of the carb,manifold vac is right off the mani. Engine can be monitored somewhat with a vac reading.Get a shop manual,they tell you all about the differnt readings but basically the higher the better and it should be steady,not jerking. Some cars used to have a vac gauge "mileage meter".Higher vac=better mileage,but really it's about the same as "light foot=better mileage. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

04-04-2008, 08:28 AM	#12
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Re: Vacuum Cluster I have an Edelbrock AirGap. Will this port in the picture work? Does any one know what "TANDEM LOCK" and "OVERSPEED" lights in a C-50 fuel gauge would indicate? Attached Images __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance.

04-04-2008, 09:12 AM	#13
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,886	Re: Vacuum Cluster Yeah,that will work,but you will need a tee on there for any other vacuum needs,ie. Trans.modulator,vac-assist brakes etc.I'm not familiar with that mani but I'm sure it came with a diagram of some sort for the hook-ups (?). __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

04-04-2008, 07:21 PM	#15
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Re: Vacuum Cluster The red warning lamps that say "BRAKE" and "TEMP" in my truck have never worked. Is there a common reason for this? I would really like the brake light to work as I leave the parking brake on every now and again on accident. It would be nice to have the light let me know they are still on and not the smell of burning brakes. __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance.

04-04-2008, 11:12 PM	#16
WorkinLonghorn Senior Member Join Date: Dec 2006 Location: Studio City, Calif. Posts: 2,886	Re: Vacuum Cluster As far as I know the brake warning light goes on when the pressure switch under the master cylinder detects a pressure imbalance,front to back,on a dual system such as your '70 would have. This lets you know is there is a leak in either the front,or back brakes. It wont go on if you forget the parking brake.(Mine has never worked,needs a new light bulb). I think the light should go on when you twist the key to start up,if not replace it. Same for the temp light,although I have a gauge so not sure on this one. __________________ '69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme.

04-05-2008, 02:21 AM	#17
oldgold70c10 Who's got steelies? Join Date: Feb 2006 Location: Morrison, Oklahoma Posts: 1,025	Re: Vacuum Cluster The temp light is not hooked up on a guage cluster. However, their is an empty contact spot in the cluster plug if you wanted to hook it up to a second "idiot light" temp sender to come on if the engine got too hot. __________________ 1969 C10 LWB W/ 250 I6 & 3spd 1970 C10 with '67 small window cab, 68 front end, blue; 305/TH350, 3.08 limited slip rear end, manual brakes, power steering; & 4-wheel drums-My daily driver. 1975 Chevelle Malibu Classic Coupe 350/th350 mint green 1970 C20 Suburban 350/700R4 4.10 gearing green & white 1978 Big 10 Silverado 350/th350, working ac, 2 tone blue-My summer daily driver 1983 GMC 1500 Sierra 305/SM465 2.73 rear end How to add a trip odometer to your 67-72 stock speedometer How to rebuild your Q-Jet My Truck Page My Youtube Channel



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04-08-2008, 07:57 PM	#18
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Re: Vacuum Cluster Well I got the Vacuum gauge this week end. It looks like someone was pulling on the engine bay side of the vacuum line and may have tweaked the gauge slightly. When I started to bend it straight I noticed that it was moving needle so I stopped. So now I have yet another stupid question for you guys. Where does the needle rest on a vacuum gauge when it is unhooked? I would think at Zero but in the picture above it is at 25. I am hoping I can bend the back of the gauge back until it reads what it should and hopefully it will work from there. Anyone have any experience with this? On another note the truck I got the gauge out of had what looked like a factory non-shifter tilt column (it had the short shaft at the bottom of the column not the longer van looking shaft). Did they make non-automatic tilts for these trucks? What would be a fair price to give him for it? __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance.

04-08-2008, 09:59 PM	#19
jay_shy SWB 4X4 CLUB Join Date: Feb 2005 Location: PA Posts: 1,088	Re: Vacuum Cluster They did make floor shift tilts but they are few and far between. If I am correct,and if its tight you could probably get 400.00 for it. Jason

04-09-2008, 04:18 AM	#20
pritch Registered User Join Date: Mar 2004 Location: Hoytsville, Utah Posts: 3,365	Re: Vacuum Cluster Hey Lehi! I don't have anything to add, just wanted to say hi from Coalville! __________________ '68 Panel Project Boogie Chillin' '68 C-10 Ol' Green

04-09-2008, 02:21 PM	#22
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,562	Re: Vacuum Cluster Vacuum gauges are calibrated in Inches of Mercury. Expressed as X"Hg. For example, when my engine idles at operating temps, it indicates 17"Hg. Cruising It shows 8" to 12" Hg. Step on it going up a hill and 5'' will drop to 0" Hg. Engine brake down a hill and it will jump to 20" Hg. If the needle bounces at 15 - 17" Hg at idle you may have a sticky valve. Also real handy for dialing in the carb. Check out this site [if it's still up]: http://www.centuryperformance.com/va...Valve%20Timing. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not. Last edited by '68OrangeSunshine; 04-13-2008 at 11:10 AM.

04-09-2008, 08:29 PM	#23
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Re: Vacuum Cluster Does anyone know if a vacuum gauge needle rests at zero when the motor is off? I think it should but I want to make sure before I start bending on the internals to get it there. Right now it is in the middle at 15 and in the picture above it is at 25. I think it got tweaked when some one took the brake system off the truck and the vacuum gauge got pulled out a bit with the vacuum line before they realized to unhook it. __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance. Last edited by lts70; 04-09-2008 at 08:32 PM.

04-10-2008, 07:08 AM	#24
lts70 1970 Daily Driver Join Date: Jun 2007 Location: Glenns Ferry IDAHO Posts: 1,038	Re: Vacuum Cluster Found some pictures that answered my question. Zero it is. Does anyone re-pop the speed warning gauge like the one in the first picture? Attached Images __________________ It's not truly yours if you didn't build it yourself or if you don't do your own maintenance.

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