HEI Hookup

[skillet]

I was remembering today previous discussions on this board about the size gauge wire for the HEI hookup. Wire size suggestions ranged anywhere from 14 gauge to 12, 10 or even 8. And while going thruogh some of my old magazine articles, I ran across a little info. on this subject in the Sept. issue of Car Craft on pg. 97. "HEI Hookup article" - "The factory used 12-gauge wire, but that's overkill in theory, only a 14-gauge wire is needed to juice a stock HEI.(though I would use bigger). The real problem is not the trigger wire itself, but low voltage at the ignition switch. Generally, the main feed wire thru. the bulkhead connector to the dash, ignition switch, and fuse panel is inadequate because the same input feed wire ultimately supplies power the head-lights, windshield wiper, rear brake lights, and heater/blower. At least the 72 Chevelle is better than prior yrs. because its horn relay-which also serves as the main pwr. distribution nexus-was relocated from its earlier location near the radiator to the firewall adjacent to the brake pwr. booster and master cylinder. Nevertheless, check for adequate underdash voltage by taking a reading off the brake or dome-light fuse. There should be at least 13.8 volts with the headlights on and the blower set to medium(with A/C cars set dash circuitry and powers the blower directly from under the hood). You also want to see 13.5 volts or more at the HEI input. If either condition is not met, install headlight relays and a high-amp integrally regulated alternator. The generic parts-store connector should work OK, but make sure it's fully seated within the HEI connector cavity and contact. It's possible to not fully engage an uninsulated terminal, resulting in intermittent contact or overheating. MAD Enterprises is one source for headlight relay kits, alternator conversion kits, and proper HEI connector and wiring instructions." Anyone tried headlight relays and what are your thoughts on them? I did install a remote solenoid(just one I bought off the shelf and made a bracket for the starter) and it solved my hot start problem and it even seems to improve cold weather starts.

[Longhorn Man]

I have done the headlight relay once on an old friends 69 GMC...made a huge improvement.

[mrein3]

I did the headlight relays last fall. I don't know what I did before that. HUGE difference.

[jjk3]

What are the benifits of a headlight relay?

[skillet]

"Using a relay can short-cut power delivery, which prevents the voltage drop associated with lengthy circuits. (Without relays, power will be routed from under the hood, to the dash area, through dash wiring and switches, and back under the hood to the part-A lengthy circuit indeed!) The alternator is the source of power, and it is mounted on the front of the engine. It's sensible to mount relays up front and let them send full power to lights, radiator fans, and other accessories. The relay provides circuit isolation, and prevents overloading existing wiring and switches. Lights ar brighter, fans are more powerful, an in general everything works better with relays." Quote according to the Mad website.

[mrein3]

Originally posted by skillet
" - Quote above deleted - " Quote according to the Mad website.

I like to add to the Mad website quote -
You also won't have to replace your headlight switch again.
By adding relays your headlight switch becomes a low current draw relay controller. Not only do your headlights get brighter but your expensive switch lasts longer.

You probably replaced your last dimmer switch too. And you won't be having to redo the melted ends on the dimmer switch connector because all the current is flowing through the relay off the battery into the light. Not off the battery, into the cab, then back out to the lights.

[billtoothaker]

I am sold. How about a wiring diagram? Source for relays

[Alex Hayley]

You can get the relays at any autoparts store. The instructions for installing the relays will be included with the relays. I am planning on tapping into the wire from my alternator to the battery. Here is a link to a thread that might help you.

http://67-72chevytrucks.com/vboard/s...threadid=85050

[mrein3]

Originally posted by billtoothaker
I am sold. How about a wiring diagram? Source for relays

The relays were ~=$5 at Checkers in a bubble pack. Don't ask the counter flunky. He/she will start hacking away at their terminal and report back that there are no headlight relays on a 1970 Chevrolet pickup...
Not that this happened to me.

I have a link somewhere to a site with a nice wiring diagram but I can't find it right now.

It is easier than you think.
Maybe somebody else has that link handy.

[Longhorn Man]

Here is a good link.
http://www.classictruckshop.com/club...ead/lights.htm

[mrein3]

Originally posted by Longhorn Man
Here is a good link.
http://www.classictruckshop.com/club...ead/lights.htm

That is the link I was thinking of.

I did two things different from that wiring diagram.

1. I used 10 gauge wire from the battery instead of 8.
2. I put an automatically resetting circuit breaker between the battery and the relays incase any thing happens.

1. I don't think 8 or 10 gauge wire makes a difference in this application. 10 can carry a lot of amps.
2. I can't imagine having a wire that doesn't have a fuse or circuit breaker protecting it.

[skillet]

Anyone know the color of the wires for the low beam and high beam lights. Thanks.