[Healeys] Speed to RPM ratio?

[Bob Spidell]

Lots of gear ratio/speed/RPM calculators out there, here's one:

https://www.summitracing.com/newsandevents/calcsandtools/gear-ratio-calculator

Enter 3 or so knowns, and solve for the unknown.

Bob


On 6/11/2021 2:26 PM, John OBrien wrote:
> Hi Guys and Gals
>
> I am trying to calibrate my tach.  I installed a Spiyda RVI - RVC 
> conversion board, because my tach was acting wierd.  Anyway, I am 
> still trying to get this setup to read correctly.  My question is, on 
> my BJ8 with standard 3.9:1 diff. what should my RPMs be in fourth gear 
> going 50 MPH , without overdrive engaged.  I'm running 165/80R15 
> tires. I'm just looking for a reference point to compare what should 
> be, and what I am reading.
>
> Any help is appreciated.
>
> Thanks
>
> John
>