Aftermarket Tachometer - How Many Cylinders

[Iplayfarmer]

I have an old tachometer in a box of random parts that I'm considering installing on my crawler. It's a Stewart Warner 824872. Is there any way to tell how many cylinders it's made for. I have four cylinders on my continental F140 L head engine.

If this is a 6 or 8 cylinder tach, is it easy to make it work with 4 cylinders?

Thanks.

 

[Roadworthy]

Basically a tachometer counts pulses. If you put an eight cylinder tach on a four cylinder engine the indicated rpm would be half the actual rpm. So if it's a six or eight cylinder tach it would indicate on a four cylinder engine but it would not give an actual readout of your engine speed. You could put markers on it for specific speeds but you'd need some other way to determine where the markers should be. The indicated rpm would be a fraction of the actual rpm, in direct proportion to that rpm.

 

[pmsmechanic]

Google "Stewart Warner 824872" and see what the internet has. Sometimes manufacturers archive old instruction sheets.

Edited to add: This is what I found. https://www.stewartwarner.com/wp-content/uploads/2018/12/120300-Traditional-Electric-Tachometer.pdf. I don't know if it's your model.

Edit #2: I changed the search to "Stewart Warner Tachometer 824872" and got a lot more results.

 

[Iplayfarmer]

I wonder if I'd be better off to sell this one on Ebay and get one that I know is right for my application.

 

[the old grind]

Most auto parts stores carry electric tachs that can be switched for 4-6-8 cyls. Think about a cushioned mount if the S-W works out.

I bot digital tachs (for diesels) that don't require a spark pulse. ~ $20 ea. Readout colors are red, green or blue and the panel is smaller than a cigarette pack.

Sensor comes with a bracket and can be adjusted several inches to align with a ~ dime-size magnet that's epoxied to a flywheel, balancer, etc.

That said, for one app I can't mount the magnet, for the other I can't mount the sensor/bkt. With spark ignition I'd have gone electric.