1952 Ford 8N original owner. My father has purchased 3 tachometers from 3 different suppliers. All work well, except they all read too high. A slow idle reads 900 rpm, half throttle reads 2200, full throttle reads off scale. Listening to the engine, clearly the tachs are reading wrong. Any idea why? Ken
1952, you have the round coil on the side, not the square coil on the front, right? Are you using an electric tach that drives off the points? I don't remember a provision for a mechanical tach on an 8n. I know some of the later engines had a worm gear on the back of the generator, but I don't remember seeing that on an 8n. If you are using an aftermarket electric tach, check and make sure it can be and is set for a four cylinder.
Hi Mitch, Actually, the tractor uses a flexible drive cable driven from the back of the governor. The tach is mechanical. Governor is located at the front right side of engine, just below the distributor. 4 speed transmission. No headlights. Not sure what other info might be pertinent.
Have you tried pulling the inside part of the cable out of the outside part of the cable? usually they are loose and you can inspect it for rust, gunk, broken wires... Or just try a new cable, can't be any more $ than three new tachs. I know nothing about the old Fords though.
Watglen, sent you an email on this. Rick
it almost sounds like the tach is reading camshaft rpm instead of crank rpm's, camshaft turns twice the revolutions of the crank (which would be true since its tied to the governor assembly) normally they have a correction gearbox that will tune the gauge to the correct revolutions.
On that engine the crank turns the cam with a gear as would be expected. The cam gear also drives another gear that is on the governor. On the model he has the later models had a tach driven from the back side of the governor. Short cable too. I'm thinking that it's supposed to have a a tach drive gear on the governor end that may be missing. I'm not real sure m 8Ns are older ones without the tach. I sent him a PM with a link to another site where he may be able to get much better advice. Rick