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MG MGA - Tachometer

I have a mechanical tach for the MGA. Can't use it b/c it's an Austin block. Willing to swap for an electronic type. Anyone interested?
Art Pearse

They show up on eBay fairly often. Sometimes you can even find a deal.
Dave McCann

Art, you might want to hang on to that so you can use the Jaeger face on a later Smiths one!
Neil McGurk

I think I tried to swap gauge faces and found there was some significant reason it wasn't possible. I don't have two gauges in front of me right now, so I can't say for sure. I know the needle can't be swapped because the shaft is a different diameter (or the taper is different, or something). I think the problem with the faces is that the angle of sweep of the mechanical and electronic gauges is different.
Dave McCann

Dave, the face mounting holes are in a different position, but are easily drilled. I think the way the light is channelled to the jewel might be different too, can't remember exactly, but nothing that isn't an easy fix. It may be necessary to swap the cases too so you can use the same bulb holder.

Anyway it is definitely do-able!

Neil McGurk

Neil, you piqued my curiosity enough for me to dig out an electronic tach and a mechanical one. The holes, as you say, are not in the same places. However a bigger issue is that the sweep angle is different. I'm going to guess that the mechanical tach sweep angle is around 280 degrees (just a little over 3/4 of a full circle), while the electronic tach is more like 250 degrees (a bit over 2/3 of a full circle). Also, the mechanical tach is linear. 3500 rpm is TDC, with 0 and 7000 at either end. Every 500 rpm looks about the same size. The electronic tach is clearly not linear. The arc length from 6000 to 7000 is at least 60% greater than the arch length from 0 to 1000.

I understand the desire to disguise modern components behind original facades (well, slightly more modern in this case), but the electronic tach innards against the mechanical tach face will not ever be accurate.

I think there are companies out there that will take an original mechanical tach and insert a modern electronic tach inside that case and make it accurate. That would most likely be a better option if you're looking for an original look in an MGA with an engine that does not have a tach drive.

For the record, I'm comparing an RVI2401/01 electronic tach against an RN2300/01 mechanical tach. Maybe there's a late electronic tach that is better suited to use with a mechanical tach face.
Dave McCann

> I think there are companies out there that will take an original mechanical tach and insert a modern electronic tach inside that case and make it accurate.

Nissonger can do that...but it's not cheap.
Andy Bounsall

This thread was discussed between 14/04/2010 and 16/04/2010

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This thread is from the archive. The Live MG MGA BBS is active now.