71 240z with L28et swap, tachometer compatibility question

[halokilller]

Which tachometer will work with my swap, the car currently has an aftermarket tach but I want to get a factory tach. I found a 73 240z tach, will this work? Otherwise, I read that 280z tachs will work.

[280zex]

The early 240Z factory tach units function differently than the 280z units. There is info here http://forums.hybridz.org/topic/60436-240z-tachometer-hook-up/

 

OR just use the aftermarket unit you have...google search does wonders

[cgsheen]

A Tach from any model Z that had an electronic ignition module will work without modification on the L28ET.  I know my '74 260Z Tach worked "out of the box".  All the 280 Tachs are the same.  IDK about the '73.  But, you can tell if it's a curent sensing Tach by looking at the back.  If it has a 4-wire connector with "two whites" (really just one wire that's looped) that loop on the back of the Tach, it's current sensing.  The later Tachs used with electronic ignitions are 3-wire...

[DCZ]

The tach on my 73 works fine with a stock L28ET swap and also after the switch to megasquirt, using the stock ignitor. I'm pretty sure it is a stock 73 tach. I don't remember exactly how I wired it but the key is to remember that the tach is driven by current, not simply voltage i.e. you can't just run a wire from the + terminal on the coil to the tach, unless that wire is actually the current feed for the coil. If that's not too confusing post back and I'll try to find my notes.

[Tony D]

As long as the coil you use doesn't vary much in amperage draw from the stock one, and you are conventionally triggering it (one coil, six cylinders) the tachometer error won't be that great.

If you put in a big honker yellow coil with pleasure ribs and oil vent holes...you might find the tach a 'bit optimistic"---like showing 7,100 at 6,000 and so on... That will require online tweakage of the cal screw on the back as outlined in the JTR Manual for the V8 Conversions.

 

Mine is off below 1,100 rpms, but spot on above that point.

 

Aftermarket tachs with a wire from the (-) coil terminal should be universal like the 260 and later tachs.

 

If it's an earlier (<74) tach that senses current, just keep the current comparable with stock and no worries.