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MG MGA - MGB electronic tacho and a non-points distributor?

Hi guys,

I have put a similar post on the MGB Technical board, but, here goes...

I've got a 5 bearing MGB engine in my A and it has been converted to negative earth.

I want to fit the "RVC" negative earth style rev counter, as shown on Barney's awesome site, because it looks pretty much like the Jaeger original.

I want to fit a breakerless ignition system, like a Lumenition, to avoid hassle with the points.

Only trouble is, apparantly the "RVC" rev couinter doesn't work with breakerless ignition systems, and I'd have to use the nasty looking "RVI" MGB rev counter. Yuck.

Does anyone out there have any experience with:
1) getting the "RVC" rev counter to work with breakerless systems.
2) if it possible to put the innards of and "RVI" into an "RVC" to make a hybrid.
3) if an alternative breekerless system will work, and it's just Lumention that's a problem?

Many thanks,

Grant :-)
G Hudson

Sorry guys, a bit of confuision and finger trouble -

I want to fit the "RVI" as shown on Barney's site, not the later, nasty "RVC", I got the letters the wrong way round!

D'oh!

cheers,

Grant :-)
G Hudson

Grant

I will have to look at my instrument to see what I have - RVC or RVI.

What is the difference?

Other than saying 'Smiths' mine has the same display as the MGA Jaegar instrument. It is working fine with my 1800, negative earth, electronic ignition.

Steve
Steve Gyles

Hi Steve,

the RVI (a la Barney) looks like the MGA Jaeger rev counter, but it just says smiths instead of Jaeger.

The RVC looks like the picture I will try to attach - the numbers are different and the red line is just a red line - very 1980s.

Cheers,

Grant


G Hudson

Grant

Mine looks like this Ebay link. http://cgi.ebay.co.uk/SMITHS-MGB-Rev-counter-Tachometer-RVI-2401-00A_W0QQitemZ380142818158QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item588247136e&_trksid=p3286.c0.m14&_trkparms=65%3A12%7C66%3A2%7C39%3A1%7C72%3A1683%7C293%3A1%7C294%3A50

It says converted to negative earth, so may be the way to go.

I bought mine from an MGB breakers yard. It was already negative earth as standard.

Cheers

Steve
Steve Gyles

Grant,

Can you use your old MGA face and needle on the RVC? It's the same principal as using MGB RVI bits. Both will need new holes drilling (but will not be visible in the black portion)
Chris Velardi has some good pictures:

http://picasaweb.google.com/chrisvelardi/MGARebuild#

(Hope you don't mind me linking your photos, Chris)

If you use the MGA casing you can also keep the original bulb holder.

I have a three bearing 1800 so use the mechanical tach. My tacho was badly faded so I got an early B Jaeger tacho that is interchangeable and identical face (except serial no.), but much cheaper s/h than MGA. The only difference was the ignition light bulb holder, so next job is to swap casings.
Neil McGurk

Steve,

thanks for the link, but the trouble is that (apparantly) that won't work with a brekerless system like a Lumenition - it needs points to work, which is the problem I've got. what ignition do you run?


Neil,

thanks for that - I wasn't sure if dials and internals were interchangeable. As they appear to be I might just get the "nasty" RVC and do a face transplant.


Nothing is ever easy, but it's good fun finding out!

Cheers,

Grant :-)
G Hudson

Grant

I use the Aldon Ignitor which is the same as the Petronix. The only warning I was given was to make sure the rev counter was connected to the correct coil terminal - whichever one that was. Will look under the bonnet tonight. (not commuting in it today, on jacks awaiting second steering rack gaiter).

I have considered fitting the original Jaeger dial, but never got round to it. After the Smiths had been in a week or two I got quite used to it and the originality aspect faded into the nice to have but not essential category.

I guess by the time you convert a 1500 car to 1800, 5-speed, 3.9 axle, wire wheels, sports screen, covered dash, BRG etc, originality becomes a little less important!!

Steve
Steve Gyles

Grant,
I am using the RVI unit on my MGA with positive ground and pertronics ignition. It reads about 500 rpm high at about 4000 rpm but I have not worried about it. I don't know if it is an adjustment or what. Have a good day!

John
John Progess

Grant

I am rubbish at electronics. However, all the revcounter is doing is measuring the pulse period , counting the pulses coming out of the coil, dividing by 4, then playing around with a SSL (suitable system of 'linkages') to give a display on a dial. I would have thought that the pulses out of the coil would be the same for a cb and non-cb system. Or am I missing something?

Steve
Steve Gyles

I use an RVI unit with a Crane ignition in a negative earth car with a Lucas coil. I've heard bad things about the Crane but I've had it over 10 years now and it still works fine so won't replace until it dies.

Anyway, the tach works fine and I've run it those 10+ years now as well.

Cheers,
Christopher

Christopher Wilson

Grant

It would seem that you have been mis-informed or are assuming that all RVC instruments are 'nasty looking'.

Just had a look at my 'nasty' RVC. Looks very much like your RVI.

Mine is a standard negative earth model, RVC2415/OOAF (see image).

Cheers

Steve


Steve Gyles

That's useful to know, It would appear that the RVC tacho has the screws for mounting the face in the vertical, the RVI is horizontal, as is the MGA, but in a slightly different position. A good way to identify the correct parts on fleabay.
Neil McGurk

Just checked the Moss parts book. The RVC2415/00AF is for negative earth MGBs August 1972 to July 1974. Moss (Europe) part number BHA5220E.

My RVC2415/OOF has 2 connectors: spade terminal for power via the ignition switch; adjacent round push-on terminal connected to the coil negative terminal.

Steve
Steve Gyles

Grant, I have an early 5 main (18GB) engine and pertronix Ignitor in my car. I'm currently using an RVI2401/OOB, modified to negative earth as per the instruction on mgaguru. It works but is not terribly accurate.

Another (somewhat expensive) option for your consideration. Nisonger can "convert" your original MGA tach to electronic operation, and calibrate it to work properly and accurately with which ever electronic igition system you're using. In essence, they replace the innards of your tach with a new electronic instrument and reuse the original face plate and dial so that it still looks like the original tach.

I sent my MGA tach off to them to have this done, but am still waiting for it to come back. Should be another couple of weeks until I can give you a first hand report on the results.
Andy Bounsall

Steve,

thanks for that. I think I have only been shown the RVC from the later cars (see my image near the top of this posting).

The fact that you have an RVC that looks like an RVI and have been awesome enough to publish the part number will make my life a lot easier - I just need to track that variant down instead of cobbling various ones together.

Many thanks, and thanks to everyone else,

Grant :-)
G Hudson

While we're on the subject, I also have an early MGB tach in my MGA. Saturday, on the way home from the Western Washington ABFM, it started reading about 1000 RPM high. Anyone know what might cause this?
David Breneman

David, are you using an electronic ignition system?
Andy Bounsall

My MGAdvisor, who sold me my electric tach, told me if I installed electronic ignition, that I should put a second wrap in the wire around the terminal on the tach . I still have points, so I can't verify that it works.

Ken
k v morton

It's a standard ignition system, and the tach is a NOS unit installed when the car was restored, five years ago. No trouble until now. I haven't run the car since the problem started last Saturday because it's been too hot here (102 Farenheit [40 C] yeasterday) to do anything but stand in the bay and drink beer.
David Breneman

May be the RVC tacho I listed above is the way to go for all those with the 5-bearing 1800. I carried out no modifications on it whatsoever and it has served me perfectly with both cb and electronic ignitions. As far as I am aware it is reading spot on and never wavers in its readings. Cost me about £25 from a breakers yard 20,000 miles ago.

Or may be I am just lucky?

Steve
Steve Gyles

I'm using the Pertronix flamethrower distributor with a 5-main MGB engine and negative ground. I had the tach rewired so it maintains the Jaeger face. Wasn't cheap but no issues with the setup (except for heat from the engine, even with 5-core radiator and electric fan it still gets friggin HOT). But is the MGA ever sweet with the 1800 engine and late overdrive, woo-hoo
Jim P

The weather's moderated here (from a high of 104 Wednesday to a high of 81 today) so I'll be able to see if the heat is what caused my tach to act up.
David Breneman

This thread was discussed between 27/07/2009 and 31/07/2009

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