1968 - 70 Factory Square Tach

• Jun 22, 2018

• #1

roadrunnerh

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Hey guys,
I have an NOS factory tach for my 68 Road Runner. I'm installing it in the dash and I wonder if it will work with electronic ignition. I have have heard both yes and no. What say you?

 

• Jun 22, 2018

• #2

gkent

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I believe the tach gets its feed off the coil (as do most non-mechanical tachs) so I think it will depend whether the coil fires once per cylinder or multiple times. If you use an MSD then I think they make a tach adapter that probably solves the problem. I'd be looking at the user manual for your ignition box to see what it says.

 

• Jun 22, 2018

• #3

gkent

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Oh, and the downside to that factory tach is that it doesn't have a very high RPM range.

 

• Jun 22, 2018

• #4

hunt2elk

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You will have to get it modified to work correctly with electronic ignition.

 

• Jun 22, 2018

• #5

roadrunnerh

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Ignition box is mopar orange box, no manual. hunt2elk, what modifications? To work properly?

 

• Jun 23, 2018

• #6

hunt2elk

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There is a new style board made that will allow your old tach to read correctly with electronic ignition. I had Shannon at Redline do one for me http://redlinegaugeworks.com/services

Auto Instruments did another http://autoinstruments.com/services.htm

RTE also used to have a square board, but I don't see it listed on their site anymore, you could call them http://rt-eng.com/rte/index.php/Main_Page

 

• Jun 27, 2018

• #7

roadrunnerh

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I installed the tach, no mods, works well, and accurate enough for me. Not drag racing this car. I was told that a factory tach will not work right with MSD type ignition, but Orange box just fine.

 

• Jun 27, 2018

• #8

Billccm

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I'm actually doing the conversion this weekend. The guys at rt-eng.com are great. Really knowledgeable engineers and helpful.

 

• Jun 27, 2018

• #9

Billccm

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MSD tach signal is a 24% duty cycle 14Vp-p square wave. I confirmed this last weekend with a oscilloscope.
The rt-eng module will work fine.

 

• Jun 27, 2018

• #10

R

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I bought a repro from classic, says it works with msd or factory haven't tried it yet. has 8000 rpm range