Aftermarket Tachometer Ratio

[InTheDogHouse]

Hi All,

Looking at a Stewart Warner electrical Hall Effect tachometer. Says it has 0.5, 1, 1.5, 2 ratios. With my 1987 6.9L NA E350 WHERE does it mount and what ratio do I need? Thanks for any/all help!

[Scoobywagon]

The ratios are likely there to allow you to mount the pickup on different parts of th erotating assembly depending on how fast they turn relative to the crank (i.e. you could put the pickup on the cam shaft using a ratio of .5 because the cam turns half as fast as the crank.) Personally, I'd look for a good spot on the crank pulley and use a ratio of 1.

[InTheDogHouse]

Thanks Scoob!