240z Tach's and Electronic Ignition

nzeder · Post by **nzeder** » Tue Aug 14, 2007 7:31 pm

For all the guys with 240z that have upgraded to electronic ignitions units (ie installed a L28 and kept the L28 EI dizzy).

I see on a number of other zed based forums (many US based) that some have trouble with the tach (either not working or bouncing around) once the convert to EI. Anyway what I found out from these US sites is that many just purchase a 280z (that is S30 not S130 or ZX) tach and swap the internals into the 240z tach housing/face. So I thought I would just get another 260z tach and use that - as surely our 260z are almost the same as the 280z....wrong so very wrong. I forgot that our 260z were still had carbs and points so they have same tach setup as the 240z. That is the signal is from the positive side of the coil and the car will not run with the tach disconnected (as the feed goes from the dizzy to the tach then back to the coil = no tach = no power to the coil).

I guess the good news for us downunder 260z tach as the 7000rpm redline like the 240z tach. The US 280z only has a 6500rpm redline. So question for all the S31 or Fairlady Z S30 owners given your cars were originally EFI and electronic ignition equipped what does your tach redline at (as I assume these will be the stock negative coil signal type tachs)

Anyway here are some pics of the 240z and a 1977 260z tach. I still will be converting these to the more modern negative coil signal type so I can remove the points and blast resistor setup (will require some minor rewiring).

old_datto_fan · Post by **old_datto_fan** » Tue Aug 14, 2007 8:52 pm

Hi Mike,

My S31 (S30 Fairlady Z) orange lines at 6000 and redlines at about 6450.

I'll be removing the dash in the next few weeks to swap it with the one from my 260Z so can take some photos of the back of it if you want some.

Just as well you pointed this out as it reminded me that I need to allow time to swap all the guages and wiring between dashes too.

nzeder · Post by **nzeder** » Tue Aug 14, 2007 9:00 pm

old_datto_fan wrote:Hi Mike,

My S31 (S30 Fairlady Z) orange lines at 6000 and redlines at about 6450.

I'll be removing the dash in the next few weeks to swap it with the one from my 260Z so can take some photos of the back of it if you want some.

Just as well you pointed this out as it reminded me that I need to allow time to swap all the guages and wiring between dashes too.

Yes that would be a good idea as it sounds like the tach in the S31 is just like the 280z unit in the US which is the modern neg coil pickup type.

The research I have done tonight shows that you can get the 240z tach to work with electronic ignition however it is questionable how accurate the tach stay with the changes. And some say they stop working with aftermarket CDI systems so for me I will just have these converted to modern type pickup, one for the 240z (the 240z tach go figure) and then the 260z unit for the 260z

You could swap the faces over at the same time and have the modern/new non loop pickup type with the higher RPM redline

old_datto_fan · Post by **old_datto_fan** » Tue Aug 14, 2007 9:25 pm

Somewhere in the parts collection I have some nice new white faces that I may yet use.

240znz · Post by **240znz** » Fri Sep 14, 2007 1:15 pm

If I change out the dizzy on my 70 to a ZX dizzy with a E1280, can I simply change the internals of my stock tach to that of a ZX? Sounds too easy to me, would this work?

nzeder · Post by **nzeder** » Fri Sep 14, 2007 9:48 pm

I guess this could work - I had Steve at Smith's Instruments here in Auckland do the conversion for me - he installed a new main board and also calibrated the tach. A good service and I am sure he would be keen to do more (I have had him now do two for me the 240z tach and the 260z tach) I believe he would also be interested in placing an ad in our club magazine. I will have dig out his business card for this contact details but he does have an ad from time to time in the NZ Classic Car.