I need a Positive earth tachometer

[Timothy Keith-Lucas]

I've tried everything, and not found an 80mm/3.15" positive earth electric tachometer. Moss doesn't have them, eBay doesn't have them, my Sprite engine doesn't have a mechanical port, zip. I've tried isolating a negative earth tach and burned out that sucker in a few seconds. 95mm tachs don't fit between the top and bottom frame on the panel. 

 

Does anyone have an answer, preferably in the US given the international shipping situation?

[straightcut]

I'm sorry, I'm not on my computer, so it's not easy for a relative computer illiterate to respond in a hurry...  If I recall correctly, you have a S2 Seven America.  The correct tach was also used on the classic Mini Cooper S and it is positive ground.  There are ways to convert + ground tachs to - ground, but that's going off topic.  If you go to eBayUK and type in this item number:  197643748882  You can at least see the tach that's original to your Seven.  Now, finding a tach like this in the U.S. is going to be a challenge.  Maybe you know someone going to the UK who can drop one in their luggage for you?

 

Hope that's helpful!

 

Mark

 

[7Westfield]

given straightcut's hint--try minimania.com

they don't show a pos ground unit on the website, but maybe they can find one

[IamScotticus]

@Timothy Keith-Lucas If you would like a test mule to do the reverse wiring hacks on, you can have this one:

Its 80mm.  I DO NOT know if it works.

 

Edited September 2 by IamScotticus

[Timothy Keith-Lucas]

Thanks to you all for your help on this frustration. Straightcut - I bought the UK Ebay mini-cooper tach. Thank you SO MUCH for the lead. I think that I will put a dummy in the place for appearances' sake, and shift by sound until it arrives. It will be a delay - I hate to close up access to the back of the panel from the top before I finish the wiring.

 

Actually, I do have an agent in the UK, but I won't need my cousin Christopher's help on this one.  Check out CKL Developments Ltd.

[jbcollier]

Repair your original.  These kits work with either negative or positive ground.

 

https://clocks4classics.com

[Timothy Keith-Lucas]

Hmmm. My trashed tach already was converted by Clocks4classics. Thank you for reminding me of this route. With one tach on the way from the UK, I think I will open the trashed tach and see what its potential is for a second go around. 

[wdb]

43 minutes ago, Timothy Keith-Lucas said:

Thanks to you all for your help on this frustration. Straightcut - I bought the UK Ebay mini-cooper tach.

 

If possible please let us know how the whole shipping/tariffing thing goes. I'm currently hitting the 'pause' button for overseas orders.

[straightcut]

16 minutes ago, wdb said:

 

If possible please let us know how the whole shipping/tariffing thing goes. I'm currently hitting the 'pause' button for overseas orders.

You are not alone, wdb!  I’m waiting and watching as well.

 

 I received an e-mail from Pemberton Imperial addressed to their U.S. customers that they were going to add an $80 charge to all orders to the U.S. (if the order was over a certain amount, the fee could be higher).  
 

It’s my understanding the tariff was 20%, so the $80 charge smells of a “gouge”…

[jbcollier]

Do you have any idea of the paperwork and filings the US is now asking for before you can ship to the US?  I think you're lucky they are going to all that bother on your behalf.  I'm sure lots of places will just drop their US business.  

[wdb]

1 hour ago, jbcollier said:

Do you have any idea of the paperwork and filings the US is now asking for before you can ship to the US?  I think you're lucky they are going to all that bother on your behalf.  I'm sure lots of places will just drop their US business.  

 

I suspect that will be highly dependent on what's being sold. For example TR6's sold like hotcakes in the US compared to other countries. Porsches also come to mind. 

[jbcollier]

We are not talking about importing vehicles, just parts.

[wdb]

Doesn't matter. The de minimis rule is gone. Everything is charged a tariff. I believe cars and parts may have different percentages though.

[jbcollier]

In theory, parts for "vintage" cars are duty-free.  Good luck explaining that to the broker if you're not business specializing in vintage car repair.

[wdb]

Continuing the topic drift, but it may be of interest to @Timothy Keith-Lucas: there are tariffs on car parts sent from the UK and EU to the US. No mention of exemptions for 'vintage' parts.

 

https://iaaf.co.uk/auto-parts-tariffs/ 

Edited September 3 by wdb

[Timothy Keith-Lucas]

The tach has been shipped without tracking information. I'm holding my breath that it will appear on my doorstep. I definitely will report on my experience - I just hope that placing the order with UK eBay was not the endo of it.

[lotsats]

I skimmed all of this fairly quickly, but it seems to me that no one brought up the fact that you could just convert your car over to negative ground. All you have to do is change the battery cables over and touch a wire to the appropriate terminal on your generator or voltage regulator to change the generator’s polarity and it will change immediately. I’ve done this with all my positive drive cars with the exception of an MGTD which happens to have a positive ground electric fuel pump that I don’t feel like swapping out.  On my Bugeye Sprite, this allowed me to buy one of the alternators in a case that looks like a generator, and I get dramatically more output to keep the battery charged and have brighter headlights. It is amazingly quick to do, and definitely cost-effective.
 

Enjoy your Seven!

[Timothy Keith-Lucas]

Lotsats, you speak with wisdom. I think I've resisted that move because each problem seemed small relative to the task of conversion, as in "how difficult can it be to buy a new tach?"  Then I find that it really is difficult to buy that tach. I'm also scared off by "All you have to do..." because that phrase often precedes months of figuring things out while I have no local guidance. And, I've invested in a positive ground alternator, etc.  Maybe the day will come. Thanks for the reminder.

[jbcollier]

You would have to replace the alternator.  A generator can be easily re-polarized.

[lotsats]

On 9/4/2025 at 1:21 AM, lotsats said:

I skimmed all of this fairly quickly, but it seems to me that no one brought up the fact that you could just convert your car over to negative ground. All you have to do is change the battery cables over and touch a wire to the appropriate terminal on your generator or voltage regulator to change the generator’s polarity and it will change immediately. I’ve done this with all my positive drive cars with the exception of an MGTD which happens to have a positive ground electric fuel pump that I don’t feel like swapping out.  On my Bugeye Sprite, this allowed me to buy one of the alternators in a case that looks like a generator, and I get dramatically more output to keep the battery charged and have brighter headlights. It is amazingly quick to do, and definitely cost-effective.
 

Enjoy your Seven!

It is really that simple. I actually changed my Bugeye Sprite to negative ground when installing a new engine a few years ago. This spring, I went ahead and changed the generator to an alternator in a generator case. This actually included the tax drive on the back of it so I stayed with the mechanical tack. All you need to do to change it to positive ground is to change the cables and re-polarize the generator. The most time-consuming part of it was reversing the battery, cables, honest to gosh! If desired, you can also get a negative ground Smith’s replica tack from India on eBay for a very low price. I have no idea why Smith hasn’t hit them up with a copyright violation. The only appearance difference I recall from the original attack in my 1966 Lotus 7 is that the numbers are written differently: 10-80 instead of 1-8, or the reverse of that, I can’t remember which and can’t look at the car right now.