49 replies to this topic

[Rubbershorts]

When I was much younger and run such gauges, this was the Smiths Vacuum gauge I ran;-
 

How is this one connected Spider? Is it just a vacuum pipe or does it use a special sender? As per pic.

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[timmy850]

Just a rubber hose on most of the old gauges. You need to have the vacuum connected to the manifold side of the carb, or the manifold itself.

Minispares sell adapters for various carb sizes if you don’t have the right port

https://www.minispar...old-adaptor-1-5

[Spider]

How is this one connected Spider? Is it just a vacuum pipe or does it use a special sender? As per pic.

 

They are a mechanical gauge and as Tim suggested, connect to the Manifold. Don't tee in to the Vacuum Advance Port, as that won't give you Manifold Vacuum.

 

If you connect it to the Vac Advance Port, this is what you'll see at small and mid throttle openings;-

 

 

The Gauge with the Blue arrow is Manifold Vacuum and that with the Red is from the Vac Advance port.

 

If you have a Brake Servo, tapping off that line would be OK just be close to the Manifold. If you don't have a Servo, then midway between the Inlet Ports, in a larger part of the Manifold would be OK.

[Rubbershorts]

How is this one connected Spider? Is it just a vacuum pipe or does it use a special sender? As per pic.

They are a mechanical gauge and as Tim suggested, connect to the Manifold. Don't tee in to the Vacuum Advance Port, as that won't give you Manifold Vacuum.

If you connect it to the Vac Advance Port, this is what you'll see at small and mid throttle openings;-



The Gauge with the Blue arrow is Manifold Vacuum and that with the Red is from the Vac Advance port.

If you have a Brake Servo, tapping off that line would be OK just be close to the Manifold. If you don't have a Servo, then midway between the Inlet Ports, in a larger part of the Manifold would be OK.

Is a guage using a 'stress/strain guage sender something different then? From everything I'd read so far was as you've described. Just a pipe fitted in the correct area to transport the vacuum information to the guage. But, whilst looking for the correct Smiths guage, I found the below.

"Pressure measurements are taken at the intake manifold by the carburetor or by the throttle body if fuel is injected. The Vacuum Gauge uses a modern stress / strain gauge sender attached to the intake manifold of the engine. You will require a sender unit for this gauge, part number 070.449."

The sender is the one I posted above. That looks like it's to be wired to something electrical.

Edited by Rubbershorts, 05 December 2024 - 10:15 PM.

[nicklouse]

You are over thinking things. If it needs a sender it will come with one. And it will be an electrical set up. If it is a mechanical one it might come with a take off the will need to be fitted to  the manifold rather than the sender.

 

just buy one and realise how pointless they are grafter you have fitted it it. (Just personal results of having one in the 80/90s I forget)

[Spider]

 

They are a mechanical gauge and as Tim suggested, connect to the Manifold. Don't tee in to the Vacuum Advance Port, as that won't give you Manifold Vacuum.

If you connect it to the Vac Advance Port, this is what you'll see at small and mid throttle openings;-



The Gauge with the Blue arrow is Manifold Vacuum and that with the Red is from the Vac Advance port.

If you have a Brake Servo, tapping off that line would be OK just be close to the Manifold. If you don't have a Servo, then midway between the Inlet Ports, in a larger part of the Manifold would be OK.

Is a guage using a 'stress/strain guage sender something different then? From everything I'd read so far was as you've described. Just a pipe fitted in the correct area to transport the vacuum information to the guage. But, whilst looking for the correct Smiths guage, I found the below.

"Pressure measurements are taken at the intake manifold by the carburetor or by the throttle body if fuel is injected. The Vacuum Gauge uses a modern stress / strain gauge sender attached to the intake manifold of the engine. You will require a sender unit for this gauge, part number 070.449."

The sender is the one I posted above. That looks like it's to be wired to something electrical.

 

 

The Gauge I had was new in the 80's. It's 90% mechanical, the only electric part is the bulb for illumination.

Now you bring this up about a sender, I know Smiths have change some of their gauges to stepper motor types. The current version may well be one of these, in which case, yes, it would need a sender.
 

[miniGTS]

Where does the vacuum gauge connect to?

[Rubbershorts]

They are a mechanical gauge and as Tim suggested, connect to the Manifold. Don't tee in to the Vacuum Advance Port, as that won't give you Manifold Vacuum.

If you connect it to the Vac Advance Port, this is what you'll see at small and mid throttle openings;-



The Gauge with the Blue arrow is Manifold Vacuum and that with the Red is from the Vac Advance port.

If you have a Brake Servo, tapping off that line would be OK just be close to the Manifold. If you don't have a Servo, then midway between the Inlet Ports, in a larger part of the Manifold would be OK.

Is a guage using a 'stress/strain guage sender something different then? From everything I'd read so far was as you've described. Just a pipe fitted in the correct area to transport the vacuum information to the guage. But, whilst looking for the correct Smiths guage, I found the below.

"Pressure measurements are taken at the intake manifold by the carburetor or by the throttle body if fuel is injected. The Vacuum Gauge uses a modern stress / strain gauge sender attached to the intake manifold of the engine. You will require a sender unit for this gauge, part number 070.449."

The sender is the one I posted above. That looks like it's to be wired to something electrical.

 
The Gauge I had was new in the 80's. It's 90% mechanical, the only electric part is the bulb for illumination.

Now you bring this up about a sender, I know Smiths have change some of their gauges to stepper motor types. The current version may well be one of these, in which case, yes, it would need a sender.

Thanks Spider, very informative as usual.

[Rubbershorts]

You are over thinking things. If it needs a sender it will come with one. And it will be an electrical set up. If it is a mechanical one it might come with a take off the will need to be fitted to  the manifold rather than the sender.
 
just buy one and realise how pointless they are grafter you have fitted it it. (Just personal results of having one in the 80/90s I forget)

Haha, thanks Nicklouse, the Smiths sender is a separate £98 add-on, so I might decide it's useless before I buy and fit one;-)

[Spider]

Where does the vacuum gauge connect to?

 

Inlet manifold.

 

 

,,,,the Smiths sender is a separate £98 add-on, so I might decide it's useless before I buy and fit one;-)

 

Wholly cow - that gets expensive fast !

I can see why the TIM brand are well on offer.

If I can ask, why are you thinking about a Vacuum Gauge ?
 

[Rubbershorts]

 

Where does the vacuum gauge connect to?

 

Inlet manifold.

 

 

,,,,the Smiths sender is a separate £98 add-on, so I might decide it's useless before I buy and fit one;-)

 

Wholly cow - that gets expensive fast !

I can see why the TIM brand are well on offer.

If I can ask, why are you thinking about a Vacuum Gauge ?
 

 

Certainly Spider. Initially experimental to see if we can get more miles out of a tank. The Minispares Tim gauge is fairly cheap so I thought it would be an interesting thing to do. Then the more I read about it, it seems a more advanced one might be useful for diagnosing faults. Opinion seems split of whether they are worth the effort though.

[sonscar]

They are colourful and move about a lot,very pleasing to the eye.Carefully used whilst driving they can improve mpg by cultivating different driving habits.Steve.

[Gaz66]

I'll get one of these for mine when it's on the road. Thing is I won't know if it's working or not as it will always be in the red 😁

[Rubbershorts]

They are colourful and move about a lot,very pleasing to the eye.Carefully used whilst driving they can improve mpg by cultivating different driving habits.Steve.

 

 

Cheers Steve. Do you run one? If so, which one? Daz.

[sonscar]

I have one in my MGB and my TR7,both second hand from autojumbles,30or more years old.Steve..