Which wire on HEI is the tach wire? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

MrC1 · 10-12-2005, 10:46 AM

I'd like to install a tach, but I'm not sure which wire I need to tap into for the signal from my HEI. Figured it's easier to ask the question here than to look it up!

76bonanza · 10-12-2005, 10:48 AM

right next to the ignition wire. There should be a wire to a switched source hooked up to it now right next to it is a male spade for you tach.

shifty · 10-12-2005, 11:02 AM

It should say on the top of the coil cover (cap, whatever).

67ChevyRedneck · 10-12-2005, 11:19 AM

These guys are of course right, but itt should be labeled as well, should say BAT on one side (for your power wire) and the other side should say TACH (at least my dizzy cap does) Don't forget to ground your tach properly or you could fry your HEI.

tomatocity · 10-12-2005, 12:52 PM

Quote:

Originally Posted by 67ChevyRedneck

These guys are of course right, but itt should be labeled as well, should say BAT on one side (for your power wire) and the other side should say TACH (at least my dizzy cap does) Don't forget to ground your tach properly or you could fry your HEI.

If it is a stock tach do you need to add an additional ground?

What size wire from the dizzy to the tach?

67ChevyRedneck · 10-12-2005, 01:49 PM

Hmmmmm, good question. Don't know if you need to ground a factory tach.... I was under the assumption that "i'd like to install a tach" meant an aftermarket one. Not good with wiring, so I can't help ya there, but 10 or 12 gage sounds familiar??? The Sunpro tach I bought had wiring long enough that it reached the dizzy without adding any wire.

MrC1 · 10-12-2005, 04:50 PM

I don't remember what they say is needed, either, but this is just a signal feed, not a major current-flowing wire. I wouldn't think it needs to much much. If I'm right, a 20ga should be fine.

Just wish I knew fo-sho.

Longhorn Man · 10-12-2005, 06:02 PM

If your dash lights temp guage and fuel guage all work fine, then there is no need to install a ground. HOWEVER... it is not a bad idea.

10-12-2005, 10:46 AM	#1
MrC1 Dork For Days Join Date: Aug 2005 Location: Dallas Posts: 407	Which wire on HEI is the tach wire? I'd like to install a tach, but I'm not sure which wire I need to tap into for the signal from my HEI. Figured it's easier to ask the question here than to look it up!

10-12-2005, 10:48 AM	#2
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	right next to the ignition wire. There should be a wire to a switched source hooked up to it now right next to it is a male spade for you tach. __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

10-12-2005, 11:02 AM	#3
shifty Questionable Join Date: Mar 2005 Location: Atlanta Posts: 13,373	It should say on the top of the coil cover (cap, whatever). __________________ If I've got anything up for grabs, it'll be here: 7-hole gauge cluster for a 67-72 p/u FREE (link) I can't check the forum daily. If I don't reply to you within 24 hours, drop me a PM! I'm (hopefully) still alive and will reply faster to a PM.

10-12-2005, 11:19 AM	#4
67ChevyRedneck Hittin E-Z Street on Mud Tires Join Date: Nov 2004 Location: Greenville, SC Posts: 23,090	These guys are of course right, but itt should be labeled as well, should say BAT on one side (for your power wire) and the other side should say TACH (at least my dizzy cap does) Don't forget to ground your tach properly or you could fry your HEI. __________________ Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride American Born, Country by the Grace of God 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications!

10-12-2005, 01:49 PM	#6
67ChevyRedneck Hittin E-Z Street on Mud Tires Join Date: Nov 2004 Location: Greenville, SC Posts: 23,090	Hmmmmm, good question. Don't know if you need to ground a factory tach.... I was under the assumption that "i'd like to install a tach" meant an aftermarket one. Not good with wiring, so I can't help ya there, but 10 or 12 gage sounds familiar??? The Sunpro tach I bought had wiring long enough that it reached the dizzy without adding any wire. __________________ Jesse James 1967 C10 SWB Stepside: 350/700R4/3.73 1965 Ford Mustang: 289/T5-5spd/3.25 Trac-Loc 1968 Pontiac Firebird: Project Fire Chicken! 2015 Silverado Double Cab 5.3L Z71 2001 Jeep Wrangler Sport 4.0L 5spd 2020 Chevrolet Equinox Premium 2.0L Turbo 2011 Mustang V6 ~ Wife's ride American Born, Country by the Grace of God 1967 CST Shop Truck Rebuild! My 1967 C-10 Build Thread My Vintage Air A/C Install Project "On a Dime" Trying my hand at Home Renovation! 1965 Mustang Modifications!

10-12-2005, 04:50 PM	#7
MrC1 Dork For Days Join Date: Aug 2005 Location: Dallas Posts: 407	Wire size I don't remember what they say is needed, either, but this is just a signal feed, not a major current-flowing wire. I wouldn't think it needs to much much. If I'm right, a 20ga should be fine. Just wish I knew fo-sho.

10-12-2005, 06:02 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	If your dash lights temp guage and fuel guage all work fine, then there is no need to install a ground. HOWEVER... it is not a bad idea.



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