Rev Counter

[rong]

I'm sure my rev counter is over reading and i wonder if anyone out there knows what revs should be showing at say 30, 50 and 80mph?
The car has a 3.7 diff, 4 speed g/box and 13inch wheels. I know that I should be able to work it out , but maths was never my strong point!
I understand that the speedo will be far from accurate but this will give me some indication of the tacho's inaccuracy.
Has anyone else experienced this problem (i.e. tacho tends to stick when engine started but a tap on the glass gets it moving).
At an indicated 70mph the tacho is reading approximatly 6500rpm

Ron
50/775

[rocket]

If your counter is reading 6500 in 4th at 70mph its along way out,id say this allied to it sticking suggests it broken.


Ian.

[gordonlund]

My Speedo & Rev counter could do with a good calibration but I'm saving for the mortgage to pay for it. Any one know of a good reputable company who can do this without excessive charges?

My Tom Tom tells me how fast I am going and I calibrate (roughly) my speedo reading from that.

From the graph attached, 70 mph is 4,000 rpm on a 3.77:1 diff in top of a four speed box.
(75 mph on a 3.54:1 diff)

This is working with a standard 13" 5 1/2J wheel shod with 13 - 165 - 80 Dunlop SP10

Regards

Gordon

[mikealdren]

Gordon and others,
There are several firms out there who repair/overhall/convert instruments. Speedy Cables seem to get good press on this site, there are also Richbrook, Richfield CAI instruments and doubtless many others.

For a tacho, it's worth considering having it converted for electronic ignition at the same time. Lots of threads on the subject, have a searhc on this site.

Mike

[david.g.chapman]

My rev counter is also starting to over read. It is probably the capacitors in the rev counter electronics deteriorating over time. Eventually they allow extra pulses from the ignition though, and you get a higher reading.

You can either get someone like SpeedyCables to refurbish it (as already stated), or if you are confident enough and know something about electronics, you could strip the rev counter and simply replace the capacitors with equivalent modern ones. I will be trying that soon.

Dave Chapman.

[rong]

Gordon,
The graph was exactly what I was looking for, many thanks!
I guess that I knew the tacho is past it's best, I just hoped that someone would suggest wiggling a wire and all would be well!!!!
The replacement capacitors interests me and I may well look at that route.
Once again, thanks to all

Ron
50/0775