Tach Questions

[poboyjo65]

Asking Barryscyclone mainly because he suggested the Crane cams XRi points eliminator to me for my stock SBF distributor,& he rebuilds these old tachs. but any input & hijack,BS is welcome.

Been using a vintage faria tach of the era. 12g. works great. (yeah I know I dont need the latter half )

So wondering if I could run 2 tachs. Could I run another one under the hood?

if so would it hurt this 4g tach ?I bought another similar tach (except its 4g )to get the mount cup off of. both are 8cyl tachs. I'm guesstimating 6gs would be back at the 0 peg. I may go a tad past that if my rev limiter ever failed but I have it set a tad under 6g I think. My cam is all in @5600 & I rarely get that high,but I could miss a gear someday. so I didnt know if the needle hit that peg would it hurt the tach?

[vicegrip]

Are these tachs both current driven?

[poboyjo65]

Are these tachs both current driven?

Been using the 12g only

[vicegrip]

Current driven,as in tach operation,not currently driven.Had to laugh,sorry.Older Ford vehicles used current driven tachs,hooked in series from the run-start position on the switch to the positive on the coil through the resistor wire.I would think those old Faria's are current driven.If so,you can hook both tachs in series before the resister and both will read accurately.If either tach is bad,the motor won't run.

[poboyjo65]

Current driven,as in tach operation,not currently driven.Had to laugh,sorry.Older Ford vehicles used current driven tachs,hooked in series from the run-start position on the switch to the positive on the coil through the resistor wire.I would think those old Faria's are current driven.If so,you can hook both tachs in series before the resister and both will read accurately.If either tach is bad,the motor won't run.

OH !!! I guess I did think you said currently driven,, Sorry I have to laugh too now! we all need a laugh now & then.
but yes one wire to tach & other wire from tach to coil ,so yes current runs thru tach.

so as long as I tie both in series before wire turns pink, right?
so consider the tach in the diagram as the first tach ,take the black wire from #1 tach & run to the red wire of #2 tach & black wire of #2 to pink wire/coil,right?. pink is where the resistor is right?



I'm thinking it'd be nice to have a tach under the hood when tuning. Another idea is to just have the wiring set up so I could simply unplug the wiring & plug in a tach under hood temporarily to tune, & take it back off afterwards. but a quick release mount would be nice for tuning -test ,leaving it on for a while if I wanted to .

[Joe Travers]

I'm thinking it'd be nice to have a tach under the hood when tuning. Another idea is to just have the wiring set up so I could simply unplug the wiring & plug in a tach under hood temporarily to tune, & take it back off afterwards. but a quick release mount would be nice for tuning -test ,leaving it on for a while if I wanted to .

Was wondering what you were up to with that flathead tach.
All in @ 3K works for me

Joe

[poboyjo65]

I'm thinking it'd be nice to have a tach under the hood when tuning. Another idea is to just have the wiring set up so I could simply unplug the wiring & plug in a tach under hood temporarily to tune, & take it back off afterwards. but a quick release mount would be nice for tuning -test ,leaving it on for a while if I wanted to .

Was wondering what you were up to with that flathead tach.
All in @ 3K works for me

Joe

Is that what these 4g tachs were for ? flatheads? I see them all the time & wondered what they were for. You got any idea what this 12g was for? I have seen one other one in a pic of a box of old tachs a guy posted one time. & still I wonder what 8cyl engine wound up that high in the 60's.

But yea Joe it's just laying around here not in use so I thought it would be a good one to see the idling & all the lower rpms when setting carb,timing etc. because the numbers are spread out a little better & easier to see & I got a steal on ebay for 29 bucks. Caught the big bidders napping I guess because the cups/brackets usually bring more closer to 100$. Guess they didnt see the cup,,,I saw a cup/bracket similar to the one that came with it sell for 139 bucks not long ago .

[Joe Travers]

Is that what these 4g tachs were for ? flatheads? I see them all the time & wondered what they were for. You got any idea what this 12g was for? I have seen one other one in a pic of a box of old tachs a guy posted one time. & still I wonder what 8cyl engine wound up that high in the 60's.

Just an assumption. Stock flatheads ran out of steam around 4K.
Only engine that could turn 12K in the '60s was Cosworth Formula One, as far as I know.

Joe

[vicegrip]

You have it right.If you put some kind of plug under the hood for temporary use,you need a jumper between the poles to run without the extra tach.

[Joe Travers]

If you have tuning OCD like me, install a good all-weather plug

Checked on the Cosworth engine specs, they didn't make up to 12K in the '60s. That came with further development a few years later.
Don't know what you have with the 12K tach. Hopped-up motorcycle?

Joe

[poboyjo65]

You have it right.If you put some kind of plug under the hood for temporary use,you need a jumper between the poles to run without the extra tach.

I was thinking just use a male & a female wire connector on tach wires & same on each end of the power wire so that when tach is not hooked up could just plug the wire back to itself.

yea Joe tuning may last for days when the mood strikes me. just to see how it acts when cold ,hot & all in between. always seems to need more tweaking.
I just bought the 12g tach on ebay for the comet. good tach, I only use the first half of it