tach question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

fjthompsoniii · 03-21-2010, 07:29 PM

I'm told there is a link you can get to put in the wire from the coil to the tach to make our tachs work with hei, anyone know anything about this?

67chevy2wd · 03-21-2010, 07:35 PM

I just ran the brown wire to the "tach" terminal on my HEI distributor. I am using a harness that I bought though so I am not sure if your wire color would be the same.

**leddzepp** · 03-21-2010, 07:45 PM

Quote:

Originally Posted by 67chevy2wd

I just ran the brown wire to the "tach" terminal on my HEI distributor. I am using a harness that I bought though so I am not sure if your wire color would be the same.

x 2

*Fitz* · 03-21-2010, 08:05 PM

Quote:

Originally Posted by fjthompsoniii

I'm told there is a link you can get to put in the wire from the coil to the tach to make our tachs work with hei, anyone know anything about this?

try here or us this PN & order from summit or Jegs.

http://www.repairconnector.com/produ...Connector.html

fjthompsoniii · 03-22-2010, 09:25 PM

I think I need to clarify the tach is hooked up and works but it's inaccurate and wont go past about 3200 rpm I'm told that is because it's hooked to hei and there is some kind of resistor or something you can put in the wire to the coil that will make the tach happy with hei.

67chevy2wd · 03-22-2010, 09:41 PM

There isn't a resistor in my harness? Can you find out if it is accurate up to 3200 rpm? Maybe it isn't calibrated right. Do you have a v6 or v8 engine?

71swb4x4 · 03-22-2010, 09:49 PM

A stock tach will work just fine with standard HEI without any modifications.

jbristo67 · 03-23-2010, 02:39 AM

I know I ordered my tach harness from GMC Pauls and it is specific for a hei set up. So that may be what you need to do

Jeffs70 · 03-23-2010, 03:37 AM

if you have switched over to HEI you will also need to get rid of the ballast resistor due to you are not using points any more, a ballast resistor can cause all sorts of issues even with the Tach.

chipflyer · 03-23-2010, 10:06 AM

Quote:

I think I need to clarify the tach is hooked up and works but it's inaccurate and wont go past about 3200 rpm I'm told that is because it's hooked to hei and there is some kind of resistor or something you can put in the wire to the coil that will make the tach happy with hei.

Mine is also a bit inaccurate, it actually reads higher than it should as RPM's increase. I have done a little research and have found that the HEI tach signal is a digital signal and the old tachometers are analog device's that expect to receive an analog signal. They just don't work very well together but can be improved if you add a tach filter. If you do a google search you will find many examples and I have added a link to an ebay item that may help in your situation. I have wanted to try one of those myself, just haven't gotten around to it.

Monte Carlo Tach filter

Here is a link to good info over on the vette forum Tach filter

fdbdw · 03-23-2010, 07:25 PM

double check the directions to see if there is a calibration that needs to be done, mine for example can be used on anything from a 2cyl to 12cyl, so when I hooked it up I had to go through the calibration proccess to get it acurate. List the brand and part # and I bet someone can help, good luck

03-21-2010, 07:29 PM	#1
fjthompsoniii Registered User Join Date: Jan 2009 Location: enumclaw wa Posts: 58	tach question I'm told there is a link you can get to put in the wire from the coil to the tach to make our tachs work with hei, anyone know anything about this?

03-21-2010, 07:35 PM	#2
67chevy2wd Registered User Join Date: Sep 2003 Location: New Salem, ND Posts: 1,558	Re: tach question I just ran the brown wire to the "tach" terminal on my HEI distributor. I am using a harness that I bought though so I am not sure if your wire color would be the same. __________________ 07 Chevy classic LBZ Duramax (a few mods) '67 Chevy 1/2 ton 2wd (in pieces) '69 Chevy 1/2 ton 2wd (on hold) '71 GMC 3/4 ton 4x4 ‘71 GMC 1/2 ton 2wd suburban

03-22-2010, 09:25 PM	#5
fjthompsoniii Registered User Join Date: Jan 2009 Location: enumclaw wa Posts: 58	Re: tach question I think I need to clarify the tach is hooked up and works but it's inaccurate and wont go past about 3200 rpm I'm told that is because it's hooked to hei and there is some kind of resistor or something you can put in the wire to the coil that will make the tach happy with hei.

03-22-2010, 09:41 PM	#6
67chevy2wd Registered User Join Date: Sep 2003 Location: New Salem, ND Posts: 1,558	Re: tach question There isn't a resistor in my harness? Can you find out if it is accurate up to 3200 rpm? Maybe it isn't calibrated right. Do you have a v6 or v8 engine? __________________ 07 Chevy classic LBZ Duramax (a few mods) '67 Chevy 1/2 ton 2wd (in pieces) '69 Chevy 1/2 ton 2wd (on hold) '71 GMC 3/4 ton 4x4 ‘71 GMC 1/2 ton 2wd suburban

03-22-2010, 09:49 PM	#7
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	Re: tach question A stock tach will work just fine with standard HEI without any modifications. __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

03-23-2010, 02:39 AM	#8
jbristo67 resident oilfield trash Join Date: Jan 2009 Location: Lubbock TX Posts: 1,465	Re: tach question I know I ordered my tach harness from GMC Pauls and it is specific for a hei set up. So that may be what you need to do __________________ 1967 SWB C10 396/400 factory air factory tach (sadly had to send to a new home) 1986 Honda 70 Fourtrax 1991 Chevrolet K5 blazer 2wd 1982 Mastercraft Pro Star 190 Stars and Stripes 2002 Chevrolet Tahoe 2011 Nissan Armada

03-23-2010, 03:37 AM	#9
Jeffs70 Registered User Join Date: Oct 2007 Location: Valley Springs, Ca Posts: 857	Re: tach question if you have switched over to HEI you will also need to get rid of the ballast resistor due to you are not using points any more, a ballast resistor can cause all sorts of issues even with the Tach.

03-23-2010, 07:25 PM	#11
fdbdw Registered User Join Date: Jan 2009 Location: colorado springs Posts: 479	Re: tach question double check the directions to see if there is a calibration that needs to be done, mine for example can be used on anything from a 2cyl to 12cyl, so when I hooked it up I had to go through the calibration proccess to get it acurate. List the brand and part # and I bet someone can help, good luck



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