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 Posted: 01-17-2008 12:16 am
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timeforwalkies
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Have the Pertronix ignition system in the car and the car is running great.  Does run a little rough at idle with the 104 cams, but I hear this is normal.
I am getting no signal to the tach and I have no idea why.
Is there an easy way to make sure the tach is still operational?
Is there something about the Pertronix that I need do that is different than the stock ignition set up?
Thanks,
Timeforwalkies

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 Posted: 01-17-2008 05:03 pm
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edward_davis
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From what I understand a certain number of the tachs just won't work with the pertronix.  For starters, the JH tach works differently from all modern tachs, in that it reads pulses in the ignition wire that goes to the coil, instead of reading the "other" post of the coil.  So the waveform the pertronix makes is different enough from the standard points-type distributor that some of the units just can't read it. 

You could also have a broken tach, like I did a year or so ago.  You can check continuity inside, to see if there is a break somewhere in the circuitry; mine had a broken connection somewhere in the coil of wire that drives the needle.  It's an easy fix, though: buy an early 70's MGB tachometer on ebay and substitute its works.  Not too tough, since it has the same redline and the mounts for the face and case of the tachometer are the same.  There are also several gauge repair shops that will sub in a brand-new tach's guts, so you can keep the look stock.  You'll have to rewire, but it'll be more precise and more accurate, too!

Edward

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 Posted: 01-17-2008 10:56 pm
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Jensen Healey
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The MGB redline is 7000 rpm????

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 Posted: 01-18-2008 07:06 pm
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edward_davis
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I mis-wrote.  The upper limit is the same on both units: 8,000 rpm.  So you can pluck the face off the MGB unit and drop it into the JH case with the JH face and it works.  The MGB redline is much lower.

Sorry,

Edward

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 Posted: 01-19-2008 01:24 am
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Jensen Healey
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I just want to drive a 7000 rpm MGB!!!

I have a pertronix and a MSD unit. I bought an VDO electronic tach that plugs directly into the MSD.

Kurt

Last edited on 01-19-2008 01:39 am by Jensen Healey

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 Posted: 01-21-2008 07:16 pm
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Mitch Ware
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I Drive a 7000 rpm MGB

 

Mitch - #19760

Attachment: new_paint44.jpg (Downloaded 82 times)

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