[Healeys] Speed to RPM ratio?

[John OBrien]

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

-- 
John O'Brien
'61 Bugeye (Lucy)
'65 BJ8 (Madelyn)