Smiths electronic Rev counter

[EdWills]

My Lotus Seven Series 3 is fitted with an original working Smiths electronic tachometer and is in the RVI series 1003/00.  I found an excellent web site from New Zealand where the author describes this model of tach and also the RVC type manufactured by Smiths.  In the article, the author notes that the RVI tach can only be used with points in the distributor, not electronic ignition (another site noted not without modifying the tach internals - which is expensive - using a kit from the U.K.).

 

Not having had any experience of electronic ignition, would a Lucas distributor that has been converted to pointless operation still be considered 'electronic' and prohibit the use of the tach that I have? I have a Lucas pointless distributor and a Bosch Blue Coil set originally from Burton U.K., but I have not installed them yet.  I am rewiring the connections to the tach (external wiring) and have the wiring diagram for the correct connections (+12v power, negative earth/ground, connection to the coil etc.). I also have 2 original good condition Ford Mopar distributors fitted with points and with extra spares for both. I may end up using one of these sans advance mechanism.  I read that Formula Ford rules require distributors with points, and the series runs very well using these apparently (Bosch/Mopar/possibly Lucas), but with constant attention given to wear on the points and adjustment of the timing.  Any electronic whizzes (digital or analog) on the forum with sage advice please? W.

[MV8]

There are many types of electronic ignitions and configurations. Perhaps you could share the article? It doesn't seem likely to be incompatible  if the ignition is not multiple discharge, capacitive, or multi-coil.

[EdWills]

Hi MV8.  Thank you.  The article is from the Triumph Owners' Club of New Zealand (Christchurch) and has been written by Alex Miller.  There are 5 downloads pertaining to the Smiths tachometers along with a guide to other Smiths instruments.  see: https://triumphclub.co.nz   

 

He has titled the papers "A Gentleman's Guide to Smiths Tachometers" and also "A Gentleman's Guide to Classic Smiths Automotive Gauges". A ton of detail is provided with diagrams and identification of the various instruments Smiths produced for car manufacturers (OEM) and also for aftermarket use circa 1960s to 1970s. Cheers W.

Edited September 15 by EdWills

[MV8]

Impressive articles. For your link to work, add an "s" for secure https.

 

 The problem is the gen 1 tach is counting amperage fluctuation instead of voltage oscillation and electronics don't use enough current for the tach transformer to function. I suppose a common high speed switching micro relay could be switched using a jumper off the coil negative wire. The relay would have a resistor sized to provide just enough amps with 14.2vdc applied. Possibly a big transistor but I think the amps would be too much for it. I've not researched it; just for the sake of discussion.  

[7Westfield]

First of all, FF does not require "points only"    the rule is--no amplifier units, so the (crappy) Pertronix and similar are fine, as long as they are a trigger only

The 123 units are not scca legal because they store 2 maps, which can be swapped electronically.  That said, RMVR has allowed them, as long as the trigger wire is exposed and not connected    they are wonderful

I have a Ford unit in the westy, with a set of the Accel HD points and mech only advance

Don't put a pertronix on a xflow--they WILL fail   not if, just when   our engine guy has had at least 2 fail on the dyno, right out of the box

 

Ford parts are Motorcraft--not Mopar   LOL

 

DO NOT eliminate the advance for a street car    you will have starting and drivability issues

We keep it in FF for starting and good idle, but we set the timing at 3500-4000 rpm

most seem to end up at 37-38 degrees @ that rpm  

Bosch dist with points in the FF for us

 

I've not had issues switching between points and electronic units--I think most tachs are smart enough

I spent the weekend at RA helping a friend with his Elva. They were chasing a misfire when I got there, and we swapped everything multiple times

--finally traced it to an intermittent coil--    no tach issues

just be sure you have the correct impedance coil for your trigger unit

 

Edited September 15 by 7Westfield

[EdWills]

Thank you very much @MV8 and @7Westfield.  My bad on the 2 counts.  I had been reading the FF engine prep. book by Jake Lamont/Tom Andresen, and back then, only points were permitted..  Obviously FF has had to change with the times a tad, and I missed the boat.  Also, apologies for 'Mopar' instead of Motorcraft.  Senior moment and not sure why that crept in?  Messrs. Lamont and Andresen recommended removing the vac advance on the Motorcraft distributor for FF use, and welding the point plates together (also on the Bosch), but I take your advice regarding the necessary idle on a road car.  Both authors also recommended the ACCEL heavy duty points, but noted that wear on the rubbing block can be excessive but specifically in FF racing of course.  

 

Do you know if Ford/Autolite/Motorcraft produce a suitable side entry distributor cap, as available for the Lucas and Bosch?  I think it would help with clearance underneath Weber carbs?  I haven't researched it, but sometimes other Ford models are used to provide parts for the Crossflow.

 

I really appreciate the advice, and may just stick with the Ford set-up, as after all, the car came equipped with this equipment, and it's not going to be anywhere near a modern Caterham version.  Points were o.k. for the car way back when and will be fine now.  I managed to buy a few sets of points and capacitors from a fellow in my city that sold his car, but the buyer didn't want many of the spare parts for unknown reasons.

 

Anyway, thanks a bunch for the advice, and I will keep on with the rebuild.

Cheers. W.

[7Westfield]

23 hours ago, EdWills said:

. I may end up using one of these sans advance mechanism. 

hopefully you mean just without the vacuum parts---don't eliminate the mech advance

that's what mine is---mech only

 

I think there was a side entry cap    I will ask our builder

a good set of stock points should be fine       Accel is prob overkill for most of us

 

I occasionally think of changing mine to electronic, just putting in a Ford pickup, and using either a Ford box or GM HEI  

OTOH   it ain't broke, so.....

[7Westfield]

caution...don't order a dist cap for a Fiesta 

they are different from a Pinto

[toldfield]

5 hours ago, 7Westfield said:

First of all, FF does not require "points only"    the rule is--no amplifier units, so the (crappy) Pertronix and similar are fine, as long as they are a trigger only

The 123 units are not scca legal because they store 2 maps, which can be swapped electronically.  That said, RMVR has allowed them, as long as the trigger wire is exposed and not connected    they are wonderful

I have a Ford unit in the westy, with a set of the Accel HD points and mech only advance

Don't put a pertronix on a xflow--they WILL fail   not if, just when   our engine guy has had at least 2 fail on the dyno, right out of the box

 

Ford parts are Motorcraft--not Mopar   LOL

 

DO NOT eliminate the advance for a street car    you will have starting and drivability issues

We keep it in FF for starting and good idle, but we set the timing at 3500-4000 rpm

most seem to end up at 37-38 degrees @ that rpm  

Bosch dist with points in the FF for us

 

I've not had issues switching between points and electronic units--I think most tachs are smart enough

I spent the weekend at RA helping a friend with his Elva. They were chasing a misfire when I got there, and we swapped everything multiple times

--finally traced it to an intermittent coil--    no tach issues

just be sure you have the correct impedance coil for your trigger unit

 

Thanks for all of this.  I've been thinking of going with a 123 for my twincam to get rid of the Pertronix that goes from ignition to paperweight without warning.

 

tom

[7Westfield]

Tom

If you decide to do it, I'll give you our builder's number in CO

he can fix you up with one and the proper coil

 

Ed

he says he's never seen a side entry cap. and he used to rebuild a lot of them, until parts dried up

[MV8]

I recall something about a volvo cap with the terminals on the side. Have to do some research.

[MV8]

Looks like a special Lucas 45D cap and distributor to go on fords. The cap is supposed to be compatible with screws or clips but I don't know that it would fit the ford body and rotor.

https://www.totalkitcar.com/2020/01/23/crossflow-distribution/

Edited September 15 by MV8

[EdWills]

21 hours ago, MV8 said:

Looks like a special Lucas 45D cap and distributor to go on fords. The cap is supposed to be compatible with screws or clips but I don't know that it would fit the ford body and rotor.

https://www.totalkitcar.com/2020/01/23/crossflow-distribution/

Thank you MV8.  This is the set-up that I purchased from Burton U.K. some time ago.  It came with the Bosch coil.  Being an electronic system, this is why I wondered about using it with the aging Smiths tach. Thanks again.  EW

Edited September 16 by EdWills
wrong coil mentioned

[EdWills]

19 hours ago, EdWills said:

Thank you MV8.  This is the set-up that I purchased from Burton U.K. some time ago.  It came with the Bosch Coil.  Being an electronic system, this is why I wondered about using it with the aging Smiths tach. Thanks again.  EW

@MV8.  I just received a reply from Alex Miller who wrote the papers, and he felt that the Burton distributor set-up would not work with the vintage Smiths tach.  He is experimenting with a points system using a 'MSD5' ignition for the benefit of his members.  The Burton dist. kit is probably using the 25D Lucas distributor with side entry cap, with the Bosch coil.  Holden Vintage U.K. also sell this same model of Lucas 25D distributor labelled as a 'Competition Distributor for tuned Ford Crossflow engines'. It is described as:  'A non-vacuum distributor which suits most tuned crossflow Ford engines using camshafts such as A2, BCF1, Piper HR270-285 and Kent 'Fireball' 234-244 in conjunction with side-draught carbs. This distributor is fitted with a side entry cap for clearance'

My notes: It is fitted with points and condenser.  It does not come with a clamp or coil which have to be purchased separately.  Holden also sell Lucas coils. Lucas has received a bad name in the past - particularly with Lotus owners claiming poor quality and reliability, but maybe these new Lucas productions are an improvement?

 

I searched the web for a side entry Ford Fomoco/Motorcraft dist. cap, found one listed on ebay, but it was incorrectly listed as it was a top entry for a Pinto.  Incidentally, the much sought after Bosch dist. for the Ford Crossflow engine (desirable for FF and used on the 1-2-3 system), apparently came from the European Ford Capri 1600 model.  A web forum with a note from a former Bosch importer advised that he could never obtain any, and they are long out of production.  I see that Ivey Engines show the 1-2-3 system on their web site, but as @7Westfield advises, this set-up is not legal with FF so they must be making it available for other road/racing activities. EW.

[MV8]

I agree about the 45d distributor with mag pickup would not work with the tach you have. I was just looking at potential caps.

 

There is a side terminal cap for old ford tractors but I don't know that it would fit your distributor.

Edited September 16 by MV8

[toldfield]

On 9/15/2025 at 11:54 AM, 7Westfield said:

Tom

If you decide to do it, I'll give you our builder's number in CO

he can fix you up with one and the proper coil

 

Ed

he says he's never seen a side entry cap. and he used to rebuild a lot of them, until parts dried up

Thanks for your offer, however I already ordered one from Berry Spencer up in Livermore.

 

Tom