Mechanical to Electrical Tachometer Conversion
Thread Starter
7th Gear
Joined: Jun 2013
Posts: 7
Likes: 0
Mechanical to Electrical Tachometer Conversion
I own a 1969 Corvette C3 and I recently converted the old 454 Big Block to a LS2 engine but the rpm tachometer stopped working. I was told by the mechanic that I need to convert the rpm tachometer from mechanical to electrical so it can adapt to the new system (ECU). I need help with the conversion and what to use to connect it straight into the ECU, because when connecting it to HP Tuner, the rpm works fine, it's just the gauge that isn't responding.
Thanks.
Thanks.
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
I own a 1969 Corvette C3 and I recently converted the old 454 Big Block to a LS2 engine but the rpm tachometer stopped working. I was told by the mechanic that I need to convert the rpm tachometer from mechanical to electrical so it can adapt to the new system (ECU). I need help with the conversion and what to use to connect it straight into the ECU, because when connecting it to HP Tuner, the rpm works fine, it's just the gauge that isn't responding.
Thanks.
Thanks.
DC
Safety Car
Joined: Aug 2001
Posts: 4,883
Likes: 11
From: North Easton Mass
You can buy an electric tach for a '75. I'm not sure which years have the same needle sweep but I don't think an 80's tach would work. You can transfer the face from your existing tach to the electric tach guts pretty easily.
To get the tach reading correctly I believe the tach setting has to be set to 3 with the tuner.
I haven't set my tach to 3 yet so it reads low but it does work.
Rick B.
To get the tach reading correctly I believe the tach setting has to be set to 3 with the tuner.
I haven't set my tach to 3 yet so it reads low but it does work.
Rick B.
Thread Starter
7th Gear
Joined: Jun 2013
Posts: 7
Likes: 0
Thread Starter
7th Gear
Joined: Jun 2013
Posts: 7
Likes: 0
You can buy an electric tach for a '75. I'm not sure which years have the same needle sweep but I don't think an 80's tach would work. You can transfer the face from your existing tach to the electric tach guts pretty easily.
To get the tach reading correctly I believe the tach setting has to be set to 3 with the tuner.
I haven't set my tach to 3 yet so it reads low but it does work.
Rick B.
To get the tach reading correctly I believe the tach setting has to be set to 3 with the tuner.
I haven't set my tach to 3 yet so it reads low but it does work.
Rick B.
The ^75 is a bit different than the 69, it would work but I'm trying to keep the interior as authentic as possible. Thanks
4th Gear
Joined: Jun 2013
Posts: 4
Likes: 0
I think you need to buy a quality one Electric relay that can give quick and adequate response to your work. I've done this type of project at my school level in my subject of Electrical. At that level it was successful. But the thing you are doing I'm not pretty sure. But I'll ask it my teacher for you.
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Last edited by David_Villa; Jun 14, 2013 at 06:21 AM.
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Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
GenIII and IV motors need a 4cylinder tach from what I am told. If you use a 75/76 Vette tach the reading won't be right. Also face colors are different than 68/71 faces lettering has greenish tint to it.
Safety Car
Joined: Aug 2001
Posts: 4,883
Likes: 11
From: North Easton Mass
Rick B.
Race Director
Joined: Jan 2000
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From: San Jose CA
Burning Brakes
Joined: Feb 2011
Posts: 850
Likes: 12
From: Shakopee MN
I've done the conversion myself
Here's a link to my thread: my-mechanical-71-to-electronic-75-tach-conversion-process.html
I bought a new circuit board from Willcox to go on the back of the 75-77 housing. I also bought a replacement filter that goes between the distributor/source and the circuit board.
I bought a new circuit board from Willcox to go on the back of the 75-77 housing. I also bought a replacement filter that goes between the distributor/source and the circuit board.
Racer
Joined: May 2010
Posts: 448
Likes: 3
From: Olathe KS
Will I have to do this when I do my conversion? My motor is an 88, but my car is a 73. I have an aftermarket ACCEL HEI dist. (if that matters)
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Sorry, it was a bad joke. Electricity doesn't actually work that way. The pulses will split equally to each side and max current will be cut in about half.
Racer
Joined: May 2010
Posts: 448
Likes: 3
From: Olathe KS
