14-09-2020, 08:49 PM
Hi David
Three speed box generally had a Smiths PA mechanical governor speedo rated at 2240 revs per mile. If you can find one of these that are correctly rated for the three speed box it is not difficult to clean the mechanism and replace the ball bearings (although you need good eyesight as the 30 ball bearings are just 1/16” diameter). I paid about £100 for mine some time ago.
However if the rear axle ratio is not 4.89 to 1 then the only way of using it is to use a correction box (several companies make these although they are not too difficult to make if you have the right tools). Mike Flannery of Magnetic speedometer repairs does repairs to governor speedos but tells me that he is not able to recalibrate the PA.
The other alternative is to buy a new “reproduction” speedo. Willie Mackenzie sells both electronic and mechanical ones I think? You can also find cheap ones on eBay manufactured in India. I have a cheap Indian rev counter that seems to work albeit 2x too fast (that might be down to me assuming a 2x take off from the drive on the bottom of the distributor?)
I’m sure others will add their experience which is probably better than mine.
Good luck
Howard
Three speed box generally had a Smiths PA mechanical governor speedo rated at 2240 revs per mile. If you can find one of these that are correctly rated for the three speed box it is not difficult to clean the mechanism and replace the ball bearings (although you need good eyesight as the 30 ball bearings are just 1/16” diameter). I paid about £100 for mine some time ago.
However if the rear axle ratio is not 4.89 to 1 then the only way of using it is to use a correction box (several companies make these although they are not too difficult to make if you have the right tools). Mike Flannery of Magnetic speedometer repairs does repairs to governor speedos but tells me that he is not able to recalibrate the PA.
The other alternative is to buy a new “reproduction” speedo. Willie Mackenzie sells both electronic and mechanical ones I think? You can also find cheap ones on eBay manufactured in India. I have a cheap Indian rev counter that seems to work albeit 2x too fast (that might be down to me assuming a 2x take off from the drive on the bottom of the distributor?)
I’m sure others will add their experience which is probably better than mine.
Good luck
Howard