17 replies to this topic

[Neildanks]

Has anyone used one on there mini ?

1. was it any good
2. where would i connect it to
3 can you really set fuel mixture / dizzy / and all what i am reading with it.
4 if so how easy is it to use.

I am thinking of getting one but would rather get some second opinions first with how tight money is at the moment

[Neildanks]

Just found this interesting article



Sounds a good resource but if i have the old cast manifold where do i connect to

[dklawson]

I do not have the Gunson kit but I do have and periodically use a separate vacuum gauge.

Yes, you can tune and diagnose using a vacuum gauge. I have never found it to be an easy tool to use when tuning an engine with multiple carbs but on those engines I have worked on with a single carb the gauge has been useful. I have never set ignition timing using a vacuum gauge as I have always had a timing light. I understand however that setting timing by vacuum is a proven technique.

There are lots of pages on the web that will explain how to interpret what a vacuum gauge is telling you for diagnostics. There are not very many that will walk you through how to use them as a tuning tool. One of the pages I had bookmarked is no longer a valid address. However, I did find the link below which may be of some interest.
http://classicinlines.com/Vacuum.asp

EDIT:
And the link below... Which unfortunately is aimed at multi-jet American carbs but the general tuning method is presented there.
http://www.diamondba.../vacuum-gauges/

Edited by dklawson, 17 June 2012 - 03:50 PM.

[minidaves]

they are very helpful at sorting some issues with car engines :)

[Neildanks]

I do not have the Gunson kit but I do have and periodically use a separate vacuum gauge.

Yes, you can tune and diagnose using a vacuum gauge. I have never found it to be an easy tool to use when tuning an engine with multiple carbs but on those engines I have worked on with a single carb the gauge has been useful. I have never set ignition timing using a vacuum gauge as I have always had a timing light. I understand however that setting timing by vacuum is a proven technique.

There are lots of pages on the web that will explain how to interpret what a vacuum gauge is telling you for diagnostics. There are not very many that will walk you through how to use them as a tuning tool. One of the pages I had bookmarked is no longer a valid address. However, I did find the link below which may be of some interest.
http://classicinlines.com/Vacuum.asp

EDIT:
And the link below... Which unfortunately is aimed at multi-jet American carbs but the general tuning method is presented there.
http://www.diamondba.../vacuum-gauges/

Where on a a series engine would this attach on a cast manifold with a std carb su

[bmcecosse]

All it can measure is how hard the engine is sucking = revs / throttle opening. You can tell that with your ears ! Seriously - spend the money on something useful......and no - not a strobe.....or a colourtune........
.

[Neildanks]

All it can measure is how hard the engine is sucking = revs / throttle opening. You can tell that with your ears ! Seriously - spend the money on something useful......and no - not a strobe.....or a colourtune........
.

What do you mean ?
how do you adjust your air and petrol mixture then, if you are so against these tools.
How do you set your engine i can set roughly by ear but doesnt mean i have it right

What shall i spend my money on then

Edited by Neildanks, 17 June 2012 - 06:36 PM.

[Neildanks]

Still need to know where i would connect to if i had the alloy manifold it had a stud for the brake servo but cant think where else i could go from on a std set up.

Anyone any ideas

[lrostoke]

I think minispares sell a carb spacer plate with a vacuum take off on it.

I have used a vacuum guage for setting timing and it worked well..I have one perminately plumbed in just for show more than anything..but it did prove useful in confirming a valve problem..gauge did exactly what it said it would :)

[Neildanks]

Thanks i will get one of those plates or drill a 1/8 tapped hole in a spare one and use an adaptor then plug it back up later

[lrostoke]

best tool i brought was a gunsons gastester...£40 off ebay, brand new.

[tiger99]

What is wrong with a Colourtune? Works ok for me.

Vacuum gauges, for fitting to the dashboard, were a popular accessory at one time on any car, and do actually help you to drive economicaly. We probably all thrash our cars about now and then, for a bit of fun, but most of the time, with today's fuel prices, it is useful to economise.

It is usual practice to drill and tap the manifold.

[dklawson]

In this case Roy the OP is not talking about dash mounted gauges (which I know you dislike). The Gunson kit is a diagnostic tool which is what you have previously said was the only use for a vacuum gauge. Of course, you know I disagree. I also think it is a good idea for any tune-up kit to include an inductive timing light. Save up a bit of money and buy an "advance type" timing light with the adjustment knob. They cost more but allow more flexibility in how you tune your engine.

Neildanks, there are several options for how you connect the vacuum gauge to the inlet manifold. If you plan on using this frequently, the easiest fix is to buy the carb spacer mentioned by Steve. When you use the gauge for tuning you plug its hose onto the barbed fitting on the carb spacer. When you are done, remove the gauge tubing and put a vinyl cap over the hose barb to keep air from getting sucked in. Contrary to what others may post, you do not need to have multiple carb spacers each with its own barbed fitting if you have multiple carbs. The reading with one hose and one barb will be accurate enough.

Drilling and tapping the manifold is always an option as Tiger said. If you choose this method, it is best done with the manifold removed from the engine so you can clean out the swarf from drilling and tapping.

[Neildanks]

I will be buying one then i have an advanced timing light but i am still not confident with using it as i find it difficult to see the marks

[tiger99]

Clean up the area, and paint the pulley black and the mark white, along with the fixed marker. Then they can be seen.

Cheap timing lights, which are uncommon nowadays, are wired in series with the spark plug, and have very limited light output. The better ones take power from the battery, and produce a much brighter flash, which makes a very big difference.