ojtwillis

New Member
Hi
I have a 1972 series 3 with a 2.25 petrol, can anyone advise me how to fit a rev counter? I was thinking about putting an old smith’s rev counter in. is this possible?
Thanks
 
IRC, There is a connector that goes on the back of the alternator. Never put one on a series though..

A Smiths would probably look the best (Please do not put those boy racer things in :eek:) but i think it would be quite expensive.

I reckon you don't need one... Engine ain't exactly quite is it? :D
 
the old type of reve couter have a positive negative and a feed taken from the coil :D, make sure you set the rev counter to 4cyl otherwise you will have some strange readings. :d

note to mseries3, there is no rev counter feed on the alternators on a series ;)
 
i think my 2.25 petrol needs a rev counter as it has a hi comp head on it a 4 port tubular manifold and a larger bore exhaust and it sounds as if it is revving up to about 6 or 7000 rpm so it may have been balanced as well so how do you fit a rev counter then?
 
I would be very suprised if a series engine will rev to 7000 RPM! Peak power is around 4000 RPM (on both petrol and diesel, according to data) so I would have thought to rev that high it would need quite a few changes.
 
it is a lot higher than any series 3 i have heard so it would be interesting to see what it actually revs to
 
With a smiths rev counter you have 3 wires, red black and yellow, the red goes to the coil + (ignition swich side), the yellow goes to the coil - (points side), and the black goes to the body ground, piece of cake.
Some of the really old ones have a current transformer, these conect in series with the + supply to the coil, if its one of these then there will be a male and female bullet connector on the back.
 
what car should the smiths rev counter be from and should it be cable driven as a lot of them i have seen are cable driven
 
Car rev counters have genrally been electronic since the 70's.
Old triumph dolomites, austin wolsely's and some jags have a seperate 4 inch rev counter, if you can find one.
Theres usually something boy racer style on ebay.
I have an instument cluster from a fiat punto with a time clock, temp guage and speedo, I also have a rover diesel cluster, when I get round to it I'll put the rover tacho in the punto cluster in place of the speedo and use the whole lot as an auxilliary instrument cluster, maybe make use of the handbrake warning light and a couple of others.​
 
Davec, did some sums, according to me a 2.25 with standard diffs, 235/85/16 tyres at 3000 rpm will be doing 96km/h is that correct?
 
Haven't got the figures with me, but that sounds about right, how fast will it go then.
Probably better off working out the figures for a lower gear.
 
i can do top speed sums i meant how high it revs got a proper smiths guage of the electronic type from the autosport show at the nec when i went there with the college on thursday it cost me £25 for a second hand one by the way what gear ratio is 4th gear with overdrive engaged
 
Davec, did some sums, according to me a 2.25 with standard diffs, 235/85/16 tyres at 3000 rpm will be doing 96km/h is that correct?

In fourth gear the main box has a ratio of 1:1. The transfer box in high range has a ratio of 1.148:1. Standard diffs are 4.7:1. So If your engine is doing 3000rpm then in top gear high ratio, the road wheels will be turning at 3000/(1.148*4.7) RPM = 556 RPM. Your rim diameter is 16" = 16*25.4 mm = 406.4mm = 0.4064 m. The radial distance from rim to tyre tread is approx 235*0.85 mm = 199.75 mm = 0.19975 m, so the outer diameter of your tyre is approx 0.4064+2*0.19975 = 0.806 m. The circumpherence of the tyre is approx 3.142*0.806 = 2.532m. So given that your roadwheel is rotating at 556 RPM the wheel will travel 2.532*556 = 1.408 km/min = 1.408*60 km/h = 84.5 km/h.
 

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