Convert 6 cylinder tach to 8
 

Hi guys

I just installed a used Westach, on 52 F1 (v8 flatty) It’s reading about 33% higher than what it should. I’m thinking it’s a 6 cylinder tach. After doing a google search a possible remedy would be to add a 1/2 watt resistor on the power/coil wire.

Before I attempt this, I would like your thoughts.

Re: Convert 6 cylinder tach to 8
 

Some tachs. have a switch inside to switch cylinder count.

Re: Convert 6 cylinder tach to 8
 

Thanks don’t believe this one does.

Re: Convert 6 cylinder tach to 8
 

A quick look at the Westach web page shows individual models for each cylinder count (4-6-8), so you are probably correct that there is no internal switch.

From what I know about this (from my own 6-12 volt tach driver), an electronic tachometer works by measuring the intervals between pulses from the ignition. As such, I don't think a resistor would help, because the interval between the pulses wouldn't change, they would just have a lower voltage. I think the only result you could expect from adding a resistor you would see is that the tachometer would cease to work at some lower voltage.

The only chance you may have is to perhaps find a place for cylinder selection in the tachometer circuitry itself. These manufacturers like to keep as much commonality as they can between different models of their devices, so they may have used the same basic circuit with optional jumpers for cylinder count.

I wouldn't count on it though.

Re: Convert 6 cylinder tach to 8
 

Thanks for the detailed response, greatly appreciated.

Re: Convert 6 cylinder tach to 8
 

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