Author Topic: tach issues  (Read 283 times)

dino67

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tach issues
« on: May 12, 2015, 02:07:34 AM »
Just looking for  little help. Just got my 67 together, and the tach reads accurate at idle but as the rpm's rise the tach is more inaccurate (5000 rpm at 60 mph) I'm using American Auto wire pointless ignition n the stock distributor and have the factory tach. I'm have a M20 trans and have a 4:10 rear end.  Do I need a new circuit board in the tach? Should I change back to points? I don't think I need a filter because the needle seems stable. Anybody else have these issues? 

My68SS

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Re: tach issues
« Reply #1 on: May 12, 2015, 04:54:26 PM »
Hmmm....tough one.....I doubt the tach has a problem. Could try replacing the condenser on the coil -ve. Otherwise switch back to points temporarily to at least prove that the tach reads correct again.
Let us know how you get on.
Rob
1968 12C SS
L34/M40
12 bolt posi 3.55

L6Ragtop

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Re: tach issues
« Reply #2 on: May 12, 2015, 09:26:41 PM »
I added an original '67 gauge set from a donor car a few years back to my car.  When I installed the tach, it seemed to behave very similar to what you describe.  Nice and steady at idle, but would swing at a much higher rate than it should have given the engine speed.  It was not erratic, just too high.  My car was not delivered with a radio, so there were no filters.  So I added a homemade RC filter at the coil connection and fixed the problem.

dino67

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Re: tach issues
« Reply #3 on: May 13, 2015, 12:58:25 AM »
Thanks for the help. I'll try a filter and a condenser. The radio isn't working either, maybe the problem is related. I won't get to it until the weekend I'll let you know how it goes.

tom

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Re: tach issues
« Reply #4 on: May 13, 2015, 10:38:13 AM »
i would contact american autowire, and ask them what you need. They might already know the answer.
69 X11 Z21 L14 glide
looking for a 69 export model (KPH) speed
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dino67

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Re: tach issues
« Reply #5 on: May 13, 2015, 09:50:53 PM »
I talked to American Autowire and they said the conversion is compatible with the factory tach. I'll try the filter and see if that will help.