Tachometer WILL **NOT** WORK W/ HEI DISTRIBUTORS - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Accelo · 02-14-2021, 01:19 PM

I am putting together a stock style dash with a tachometer. I would prefer the 8K Rpm limit style tach. Can anyone add information to why these tach's will not work with HEI?

Below is the provided disclaimer;

For all of you fanatics out there, we have finally reproduced an original looking tachometer to fit correctly in you original instrument cluster with only minor modifications. Tach kit includes everything needed to convert to a tach dash; tachometer, lens, printed circuit, wiring harness, & 2 piece metal housing. WILL **NOT** WORK W/ HEI DISTRIBUTORS

What I am more concerned with is if the tachometer will work with the computer output from the LS1 style computer. I see the addition of a pull down resister is required with some/all of the computer rpm connections.
Rick

**kwmech** · 02-14-2021, 03:23 PM

That's a good question, every truck I've had with a tach or put a tach into did not matter whether or not it had HEI. Link to the maker

Lee H · 02-14-2021, 03:42 PM

Since it's a "stock style" VS stock you can have the tach internals rebuilt with VDO internals and it will work with HEI. I had this done about 10 years ago, works well.

heskahoka · 02-14-2021, 08:06 PM

I had the same concern when I decided to put a factory looking tach in my truck along with an HEI distributor.

Here is a quick explanation of why HEI is different:
https://www.americanautowire.com/vie...c-distributor/

I ended up going with a go between interface box called TachMatch (model TM-03). It can take the signal from the HEI and converts it into the correct pulse pattern for the tach.
https://technoversions.com/TachMatch.html#itworks
I mounted the unit above the steering column behind the instrument cluster. They had great technical support too.
Works flawlessly.

On their website, it states that the unit can take a signal from the HEI or ECU; it has to correct pull-up resistor for the ECU.

Hope this helps.
-M

Andy4639 · 02-14-2021, 08:20 PM

I've done several trucks with stock GM HEI and never had a problem with the truck tach's. The last one I did worked for a while but quite. I sent it off and had it fixed. I added a 5amp fuse to it per the guy that fixed it and it's been fine ever since but no filters on any of them.

Mike C · 02-14-2021, 08:37 PM

Quote:

Originally Posted by Andy4639

I've done several trucks with stock GM HEI and never had a problem with the truck tach's. The last one I did worked for a while but quite. I sent it off and had it fixed. I added a 5amp fuse to it per the guy that fixed it and it's been fine ever since but no filters on any of them.

Where is the fuse Andy? Power line or the signal? I would assume power, but you know how assume works...

Andy4639 · 02-14-2021, 09:14 PM

Quote:

Originally Posted by Mike C

Where is the fuse Andy? Power line or the signal? I would assume power, but you know how assume works...

Yes the power wire out of the fuse block. I've never had one to quit but this one came from brothers. They made it good and said they didn't need the old one back so I sent it off and had it fixed as well.
Here is the thread to mine.

http://67-72chevytrucks.com/vboard/s...d.php?t=803315

**StingRay** · 02-17-2021, 10:25 PM

I ran a factory tach in my 72 with an HEI for 20 years. Why exactly is it that it is not supposed to work? Lots of people have run them just like me.

**LockDoc** · 02-18-2021, 01:32 AM

Quote:

Originally Posted by StingRay

I ran a factory tach in my 72 with an HEI for 20 years. Why exactly is it that it is not supposed to work? Lots of people have run them just like me.

I read it that he will be using an aftermarket tach. Not all of them will work with an HEI out of the box. That is what he is referring to.

LockDoc

**tdangle** · 02-18-2021, 02:14 PM

I have a Brothers 8K tach upgrade. It's worked great with 3 different HEI distributors so far.

Andy4639 · 02-18-2021, 02:22 PM

Quote:

Originally Posted by tdangle

I have a Brothers 8K tach upgrade. It's worked great with 3 different HEI distributors so far.

Are you running the 5amp fuse? Mine has been good ever since I installed the fuse. It has been the only one that was aftermarket for me. All the rest have been old factory tach's and never had a problem with them.

Accelo · 02-18-2021, 04:27 PM

The consensus seems to be they will work without major issues on the HEI. Unsure why they posted the disclaimer. Covering their A** is the only thing that comes to mind.
Rick

**tdangle** · 02-19-2021, 08:52 PM

Quote:

Originally Posted by Andy4639

Are you running the 5amp fuse? Mine has been good ever since I installed the fuse. It has been the only one that was aftermarket for me. All the rest have been old factory tach's and never had a problem with them.

Not yet, I keep meaning to install a fuse, but haven't yet. It's only been a couple of years now, don't want to rush into it.

Andy4639 · 02-19-2021, 10:01 PM

Quote:

Originally Posted by tdangle

Not yet, I keep meaning to install a fuse, but haven't yet. It's only been a couple of years now, don't want to rush into it.

I never had either until this one.

02-14-2021, 01:19 PM	#1
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,159	Tachometer WILL NOT WORK W/ HEI DISTRIBUTORS I am putting together a stock style dash with a tachometer. I would prefer the 8K Rpm limit style tach. Can anyone add information to why these tach's will not work with HEI? Below is the provided disclaimer; For all of you fanatics out there, we have finally reproduced an original looking tachometer to fit correctly in you original instrument cluster with only minor modifications. Tach kit includes everything needed to convert to a tach dash; tachometer, lens, printed circuit, wiring harness, & 2 piece metal housing. WILL NOT WORK W/ HEI DISTRIBUTORS What I am more concerned with is if the tachometer will work with the computer output from the LS1 style computer. I see the addition of a pull down resister is required with some/all of the computer rpm connections. Rick

02-14-2021, 03:23 PM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	Re: Tachometer WILL NOT WORK W/ HEI DISTRIBUTORS That's a good question, every truck I've had with a tach or put a tach into did not matter whether or not it had HEI. Link to the maker

02-14-2021, 03:42 PM	#3
Lee H Registered User Join Date: Jun 2010 Location: Upland Ca Posts: 4,139	Re: Tachometer WILL NOT WORK W/ HEI DISTRIBUTORS Since it's a "stock style" VS stock you can have the tach internals rebuilt with VDO internals and it will work with HEI. I had this done about 10 years ago, works well. __________________ 1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703

02-14-2021, 08:06 PM	#4
heskahoka Registered User Join Date: Dec 2017 Location: Albuquerque NM Posts: 32	Re: Tachometer WILL NOT WORK W/ HEI DISTRIBUTORS I had the same concern when I decided to put a factory looking tach in my truck along with an HEI distributor. Here is a quick explanation of why HEI is different: https://www.americanautowire.com/vie...c-distributor/ I ended up going with a go between interface box called TachMatch (model TM-03). It can take the signal from the HEI and converts it into the correct pulse pattern for the tach. https://technoversions.com/TachMatch.html#itworks I mounted the unit above the steering column behind the instrument cluster. They had great technical support too. Works flawlessly. On their website, it states that the unit can take a signal from the HEI or ECU; it has to correct pull-up resistor for the ECU. Hope this helps. -M

02-14-2021, 08:20 PM	#5
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,936	Re: Tachometer WILL NOT WORK W/ HEI DISTRIBUTORS I've done several trucks with stock GM HEI and never had a problem with the truck tach's. The last one I did worked for a while but quite. I sent it off and had it fixed. I added a 5amp fuse to it per the guy that fixed it and it's been fine ever since but no filters on any of them. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

02-17-2021, 10:25 PM	#8
StingRay Senior Member Join Date: Mar 2000 Location: Saskatoon,SK,Canada Posts: 2,476	Re: Tachometer WILL NOT WORK W/ HEI DISTRIBUTORS I ran a factory tach in my 72 with an HEI for 20 years. Why exactly is it that it is not supposed to work? Lots of people have run them just like me. __________________ Saskatoon, Saskatchewan Canada

02-18-2021, 02:14 PM	#10
tdangle Senior Member Join Date: Mar 2005 Location: Jurupa Valley, Ca Posts: 1,209	Re: Tachometer WILL NOT WORK W/ HEI DISTRIBUTORS I have a Brothers 8K tach upgrade. It's worked great with 3 different HEI distributors so far. __________________ Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC

02-18-2021, 04:27 PM	#12
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,159	Re: Tachometer WILL NOT WORK W/ HEI DISTRIBUTORS The consensus seems to be they will work without major issues on the HEI. Unsure why they posted the disclaimer. Covering their A** is the only thing that comes to mind. Rick



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