Hi all.

just trying to get an idea as to whether or not my old style tacho is reading correctly? It has a screw on the back of it in which I believe is called a potentiometer? Or something like that so yes it can be adjusted. And yes it is switched onto the 8 setting. So this is in kilometres per hour as I’m in Australia. My diff ratio is 2.92. Trans is a 727 Engine is a mild 318. Rear tyres are a 235/60/15. So at 100 kmph my tacho is reading 2,600 rpm.

can anyone verify if this sounds correct please?
tanku.


edit. Mr google tells me 100kmph is 62.1MPH.

 

Id say it's close but if you have a smartphone you can download an app for a speedometer in your phone. It's GPS and very accurate then you can verify you speedometer.

 

Hello mate. I do in fact have an speedo app in which I installed on my phone when my 15 inch wheels went on as I wanted to see how much difference there was going 14 to 15! To my surprise my speedo is fairly accurate so I know that is at least okay.

 

Like I've said it's been awhile since I've used a gear that high but but it sounds about right.
Just what are you trying to determine, gear ratio or transmission slip.

 

2500 seems high for that rear end gear ratio, in my opinion. like, big time.

 

Hi folks. I also am still curious but I managed to borrow a friends digital timing light/tacho yesterday and while in the shed the revs pretty well matched what his digital tacho was reading. Whether or not it’s different while driving I don’t know. I tried it through all rev ranges. The only real difference was at idle! His digital tacho was reading 780rpm and mine was more like 650rpm but I can live with that. It was the higher rev range I was interested in.
so perhaps it may be correct?? In the next few weeks I’m booking it in for a dyno tune as my carby and possibly the new distributor are not set up properly so you would think that his equipment would be accurate?

 

trying to determine if tacho is reading correctly. That is all.