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#1
02-28-2006, 12:46 PM
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Factory Tach
I am about to purchase an in-dash factory tach from a '70 GTO. The seller warned my against running the Tach with HEI. He stated that he had done this in the past and it results in a burnt out diode.
Can anyone verify this? Is there a way to prevent the diode from burning out with an HEI? |
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#2
02-28-2006, 01:56 PM
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I know i had problems with my hood tach, untill it was set up for HEI, so maybe the dash tach is the same. I don't know what they did thou.
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#3
02-28-2006, 03:14 PM
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how do u set it up for HEI? what is needed?
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#4
02-28-2006, 03:14 PM
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Don't know why it would burn out. Can't think of a reason unless someone modified the circuit incorrectly.
George |
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#5
02-28-2006, 04:05 PM
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Quote:
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#6
02-28-2006, 04:53 PM
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hei tach
i burnt one w/ my hei distrib. i'm in the process of trying to figure out how to fix it.
Aaron |
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#7
02-28-2006, 05:20 PM
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HEI tach
Spoke to "the tach man" he said that the circuit needs more voltage, not less w/ an HEI. Apparently its necessary to add 12V of voltage to get it working.
The good news is I didn't burn my tach out! Aaron |
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#8
02-28-2006, 05:33 PM
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There are basically two kinds of tach circuits. The early type needs only the coil (-) signal and ground to work. Later designs, and most aftermarket tachs need 12V power in addition to the other two connections mentioned above.
The early type should work with HEI, but may need to be recalibrated. The second type is more accurate and should work with either system without needing a recal. Neither of the above should be connected directly to the coil in a MSD ignition system. Don't know what your "tach man" means unless he's saying the tach also needs the power connection. George |
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#9
02-28-2006, 06:32 PM
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I'VE RAN A PONTIAC HOOD TACH WITH MY H.E.I. FOR 10 YEARS WITH NO PROBLEMS.
I TOOK THE COIL WIRE ON THE HOOD TACH HARNESS, ATTACHED A FACTORY PLUG AND PLUGGED IT IN THE TACH SIDE OF THE DIST. |
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#10
02-28-2006, 06:46 PM
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I've tried that and it didn't work...
He was saying it would need the power connection. (From what i gather). I'm no expert concerning this. Just have this problem (tach doesn't work w/ the HEI). Everytime i've researched it on this site, it seems like nobody's had the issue but me, until I read this post. When you say that an MSD coil is too hot, why would other HEI systems not be? |
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#11
03-05-2006, 02:12 AM
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Been running HEI for 12 years with a factory hood tach, never any problem.
__________________
http://ultimategto.com/cgi-bin/showc...71/71_00075_18 |
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