Smith's Tach settings

[my427cobra]

Just curious as I may have messed up my Smith's Tach settings as I was messing about under the dash.

My Smith's tach has a 8-6-4 cyl rotary switch on the back. If the switch was disturbed and moved to the 4 cyl setting, would my V8 appear to be running at twice its RPM:

Example: the V8 is running at 1000 RPM but the tach says 2000 RPM.

Can anyone help?

Cheers
Greg

[LMH]

Not sure but have you switched it back to 8 cylinder? Does it work?
Larry

[my427cobra]

I'll reset the switch this morning and run the car to confirm.

I researched the info on the net and confirmed my suspitions. A 4 cyl fires twice per revolution and an 8 cyl fires 4 times per rev.

So a 4 cyl tach on an 8 cyl engine would read twice the actual engine rpms.

Cheers
Greg

[my427cobra]

Here's a pic of the back of my tach. Rotary dial for three settings: 8-4-6 cyl .

But there are four detents as you rotate the dial - see white markings in pic:



Can anyone tell me which is the correct position for 8cyl?

I guess I could do trial and error.

Cheers
Greg

[my427cobra]

I've sent an e-mail to Nosinger hoping they can get me an answer before I start a trial and error process.

Anybody have the answer?

Greg