Aftermarket tach, MSD ignition box

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

77 K20

Full Access Member
Joined
Nov 9, 2012
Posts
3,075
Reaction score
3,044
Location
Montana
First Name
Mike
Truck Year
1977
Truck Model
K20 5" lift
Engine Size
HT383 fuel injected
I'm in the process of wiring up a MSD ignition box and they say the tach cannot be hooked up to the negative side of the coil. (not sure why, does anyone know why?).

Instead they say hook it up to the grey tach output wire.

I have issues with this. The grey wire needs to go to my Edelbrock E-street EFI controller. THEY say if you tee in a tach into that signal things can get messed up (won't run, won't run right, issues, sadness)

Another issue is MSD says for Autogauge tach gauges I'd need to buy a "tach adapter" which is $70!! If this is the case I'm thinking I'd ditch that tach and switch to a VDO tach to match some of my other gauges. They don't need the tach adapter.

Why can't things be more simple?
 

Frankenchevy

Proverbs 16:18
Joined
Jan 3, 2018
Posts
5,905
Reaction score
7,252
Location
USA
First Name
Jeremy
Truck Year
Square
Truck Model
CUCV
Engine Size
Small
Does the edelbrock EFI controller have a “CAN Bus” output?
 

77 K20

Full Access Member
Joined
Nov 9, 2012
Posts
3,075
Reaction score
3,044
Location
Montana
First Name
Mike
Truck Year
1977
Truck Model
K20 5" lift
Engine Size
HT383 fuel injected
Nope- no canbus
 

Camar068

Supporting Member
Supporting Member
Joined
Feb 5, 2014
Posts
4,124
Reaction score
2,963
Location
Kentucky
First Name
David
Truck Year
1986
Truck Model
K10/LM7 5.3/4L60e/np208/3.73/32"
Engine Size
10 yrs Air Force
maybe the signal is only strong enough for one output? Maybe put a pull up resistor on it? Look around on the net and maybe call Edelbrock and see what they say. That $70 adapter might be just that....a pull up resistor. Please look around the net and also make the call as I'm just guessing. Don't want you to blow anything on a whim.

Totally different setup, but on LS swaps, sometimes you have to put a resistor to the tach wire and 12V (pull up resistor setup) to get the tach to work. I had to do this on my truck to get it to work.
 

Camar068

Supporting Member
Supporting Member
Joined
Feb 5, 2014
Posts
4,124
Reaction score
2,963
Location
Kentucky
First Name
David
Truck Year
1986
Truck Model
K10/LM7 5.3/4L60e/np208/3.73/32"
Engine Size
10 yrs Air Force
Disregard above. I'm seeing the same thing your seeing on the net.....you need the adapter.
 

77 K20

Full Access Member
Joined
Nov 9, 2012
Posts
3,075
Reaction score
3,044
Location
Montana
First Name
Mike
Truck Year
1977
Truck Model
K20 5" lift
Engine Size
HT383 fuel injected
Got everything wired in but I left my tach hooked up to the negative side of the coil. Sure enough, it doesn't work. Needle doesn't move at all.

Doesn't make sense to me to spend $70 for an adapter for a $65 tach.

Looking at the VDO tachs that will match my other gauges. These ones do not need any sort of adapter according to MSD.

The VDO tachs are meant to sink/flush mount into your dash. I need to find some sort of pod/cup to drop it into.
 

Forum statistics

Threads
41,858
Posts
903,636
Members
33,371
Latest member
Linemanjl
Top