The 'E' Type Forum

This is a shout out for Speedograph Richfield.

My tacho has been less than satisfactory since the rebuild was completed. The tacho with a Spiyda RVI to RVC conversion for the 123 dizzy had not been satisfactory and I got fed up with the calibration being out (despite my best efforts) and needle waving about all over dial. So I decided to send it to Speedograph for their conversion. It was returned after about 3 weeks and now is first class The needle is rock steady and reads the proper rpms all the time. MAGIC! They even pained the case nicely.

Thanks Tim. Excellent.

Jerry, did they, or would they, adjust the rev counter and the drive generator as a pair ?

As the former is interpreting the volts supplied by the latter, and the latter is notoriously, let’s say, individual, it would seem obvious that the two should be set up as a pair, no ?

Edit - ah, RTFQ. I see “conversion” - does this make the instrument oblivious to the generator voltage, or does it now run off the coil ?

And what’s the $$$ damage ?

Rory,

My car is a S2, therefore the tacho is driven by signal from the coil. I have the 123 dizzy.

I'm sure I have read on here that there is no need to convert an RVI tacho, it will work as is. Not sure I believe it. So there's no signal generator on the camshaft.

My tacho was converted RVI to RVc using a Spiyda converter but the instrument never worked to my satisfaction, I had several problems.

First, I found that under acceleration the needle would rise to maybe 2,000/2,500rpm and stop there till I lifted off the gas pedal. It would then jump up and drop as I changed gear. I found this was caused by too much end float in the spindle shaft. Under acceleration the whole rotating part would move backwards (effectively) and the rotor would touch the magnet block and stick. There's an adjustment screw through which the spindle passes which needed adjusting to reduce movement of the spindle.

However, 2nd, the needle was still erratic, did not seem to read appropriate revs. I tried calibrating it to no avail. Sent the instrument to Spyida for checking, they replaced the RVI/RVC converter but it was still erratic.

So I sent the tacho to Speedograph Richfield. They replaced the RVI/RVC converter, calibrated the instrument, painted the shell and sent it back in about 3 weeks. £112 total including VAT and P&P and now it works properly, needle movement smooth and accurate. Superb!

JerryL770 wrote: ↑

Sat Mar 15, 2025 7:13 am

I'm sure I have read on here that there is no need to convert an RVI tacho, it will work as is. Not sure I believe it.

There isn't a need to convert it if you wire it up the new electronic distributor and coil correctly but that said your problems appear to be related to the Spiyda conversion and wear in your movement.

Speedograph Richfield have clearly done a good job in fitting a convertor that works and returned your tacho in great condition for a reasonable price.

Thanks for that John.

A bit academic for me now but I think it would be good to know and maybe helpful for later readers of this, to know how the tacho can be wired for a 123 dizzy to work without any other conversion necessary.