14 replies to this topic

[hoppus]

Having real trouble finding a rev gauge to match my speedo.

This is perfect size and style but its for a 6 cylinder car. Can i convert it to be used on a 4 cyl car?

 

http://www.ebay.co.u...016.m2518.l4276

 

[Swift_General]

Yes you could. A couple of ways of doing this I can think of. Either by replacing the face with a bespoke made face with markings to account for the fact that the rev counter would otherwise under read by a third. The better solution would be to do it electronically and either buy or design a device that will increase the frequency of the feed from the coil by a 50%. If it were me I think I would just keep looking I'm afraid.

Edited by Swift_General, 15 March 2015 - 06:56 PM.

[Spider]

As Swift_General has suggested, an electronic frequency divider could be used.

 

This is one such a 'black box' device, which although it is intended for electronic speedos, does work equally well on tachos

 

http://www.jaycar.co...MODULE/p/AA0376

 

or get in touch with Chris at Spiyda Design, I think he may already have a suitable black box and can assist in hooking it up and getting it working. He also have a page on his website which may guide you though it all

 

https://www.spiyda.c...ter-calibration

 

<edit: It looks awfully similar to some of the Triumph ones (I think) so it maybe worth looking at some of those, however while I haven't dismantled one of those, being that it's a Smiths / Jaggar, it wouldn't surprise me if there isn't an internal jumper>

Edited by Moke Spider, 15 March 2015 - 07:10 PM.

[dklawson]

The gauge on eBay is similar to those used in mid- to late-1970s Triumph Spitfires except the needle is different.  It also is like some of the early 1970s MGB tachs.  Keep in mind that bezels are interchangeable and paintable.  If you have a chrome bezel and want black... paint it.  If you want chrome, there are lots of places selling new replacement bezels that will work OR you could buy another used speedo or tach and transplant its bezel.

 

Triumph Spitfire Dash... wrong needle  (earlier Spitfire tachs are cable driven and have a VERY different needle)

http://i217.photobuc.../DSC_0204-1.jpg

 

 

Early 1970s MGB dash.  Similar shape needle, different needle hub, chrome hub and bezel.

http://assets.hemmin...7001-1000-0.jpg

[gazza82]

Having real trouble finding a rev gauge to match my speedo.
This is perfect size and style but its for a 6 cylinder car. Can i convert it to be used on a 4 cyl car?

 

You will find it hard as few cars had a speedo as large as a Mini. Most like the MGB shown are the standard 80mm dia dials. The one listed is 4" or 100mm.

You could try speedycables to see if they can convert it.

Edited by gazza82, 15 March 2015 - 11:52 PM.

[hoppus]

Thanks for the replies.
Here's my Speedo.
It's an old lotus one I refurbished. I can replace the bezel and glass that's no problem it's finding something somewhat similar http://s13.postimg.o..._001157_HDR.jpg

I need a 100mm RVC gauge :/
I know they have them new. But they are £160!

[dklawson]

The eBay tach does mach your Lotus gauge better than anything I found and posted.  I suggest contacting Chris at Spiyda Design as Moke Spider suggested earlier.  Their tach conversion board should allow you to calibrate the eBay tach yourself at home.

[The Principal]

These guys can modify it, not the cheapest but they are good they can also supply new Tacho's - http://www.speedycables.com/

[hoppus]

These guys can modify it, not the cheapest but they are good they can also supply new Tacho's - http://www.speedycables.com/

 

I was going to send them my speedo actually, Ill see how far out it if first, I have a K-series mini haha 

[hoppus]

The eBay tach does mach your Lotus gauge better than anything I found and posted.  I suggest contacting Chris at Spiyda Design as Moke Spider suggested earlier.  Their tach conversion board should allow you to calibrate the eBay tach yourself at home.

 

Ill contact them :)

However by the time i get the tacho and a conversion board, it might cost the same/ close too a new one :)

[Spider]

 

The eBay tach does mach your Lotus gauge better than anything I found and posted.  I suggest contacting Chris at Spiyda Design as Moke Spider suggested earlier.  Their tach conversion board should allow you to calibrate the eBay tach yourself at home.

 

Ill contact them :)

However by the time i get the tacho and a conversion board, it might cost the same/ close too a new one :)

 

 

I did think of suggesting an instrument company, like SpeedyCables when I made my post yesterday, however while I respect that they guys do need to make a living, I am fairly sure that their charges would be around 50%+ that of a new gauge. If I was presented with a quote like that, I know which way I'd go. None the less, it's only a phone call!

[ibrooks]

OK - that's exactly the gauge I used in my Mini (I used the entire gauge set from a Scimitar). I did the conversion by finding an MG tacho with the same scale and I swapped the gauge face and needle to the MG tacho. There are a couple of different models of tacho so you would need the right one from a 4-cyl car to do this swap - I've seen some where the two screws that hold the face on are horizontal across the middle whilst others have them vertical, there may well be other differences.

 

Plan B was along these lines

 

http://www.extraefi....obra/Page24.htm

 

I did get part way but then came across the MG gauge so took the easy way out.

 

Iain

[hoppus]

OK - that's exactly the gauge I used in my Mini (I used the entire gauge set from a Scimitar). I did the conversion by finding an MG tacho with the same scale and I swapped the gauge face and needle to the MG tacho. There are a couple of different models of tacho so you would need the right one from a 4-cyl car to do this swap - I've seen some where the two screws that hold the face on are horizontal across the middle whilst others have them vertical, there may well be other differences. Plan B was along these lines http://www.extraefi....obra/Page24.htm I did get part way but then came across the MG gauge so took the easy way out. Iain

Interesting so you used two gauges to make the perfect one lol

[dklawson]

Interesting so you used two gauges to make the perfect one lol

 

That's not too uncommon really.  

 

Many of the classic cars from the early 1960s used the Smiths RVI tachometers which are not very compatible with electronic ignitions.  To this day it remains fairly common for people to buy a later Smiths RVC type tach and mount the older RVI face to it to keep the original look of the dash but have a tach that can work with electronic ignitions.

[ibrooks]

 

OK - that's exactly the gauge I used in my Mini (I used the entire gauge set from a Scimitar). I did the conversion by finding an MG tacho with the same scale and I swapped the gauge face and needle to the MG tacho. There are a couple of different models of tacho so you would need the right one from a 4-cyl car to do this swap - I've seen some where the two screws that hold the face on are horizontal across the middle whilst others have them vertical, there may well be other differences. Plan B was along these lines http://www.extraefi....obra/Page24.htm I did get part way but then came across the MG gauge so took the easy way out. Iain

Interesting so you used two gauges to make the perfect one lol

 

 

Yep - but I've still got the MG gauge with 6-cylinder guts.

 

I keep meaning to assemble the above circuit to make it useable again but then I might just autojumble it someday with a silly cheap price like 50p and smile to myself because I'm not around for the punchline.

 

Iain