SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: spectralen on September 30, 2017, 12:01:49 PM
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I'm replacing my mallory mag dist. with a DUI HEI. I'm thinking of replacing my ignition switch wires with all 10 gauge. The red batt wire looks to be at least 10 gauge already but the white and purple look to be thinner. To achieve the 12 volts at the dist I believe running a thicker wire than stock will be needed going from the switch to the distributor.
Can anyone give me an idea of what they're using?
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I had to change the original 40 year old wire from the switch to the electrical block. Boat would not fire until I did due to voltage loss but I used the same size wire, fires every time. But you are correct HEI just will not work with less voltage I also run through a relay to keep the volts steady
1977 Challenger
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Couple pictures of mine located my relay below the aluminum that the electrical block attached to. You can see the mounting screw for the relay from the top picture
1977 Challenger
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Can you explain the relay system?
Is the relay for the HEI?
I have seen the slave solenoids for the starters, the relay your talking about is something else....?
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The relay helps maintain and or boost the minimum 12 volts it needs to fire
1977 Challenger
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It looks like in your pic that your relay has the ignition wire from the switch, ground, and then the HEI lead?
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Also since the demand for voltage is so high with HEI if it's to low it will fry your module the relay helps maintain the needed voltage any cheap relay should work Bosch or any other.
1977 Challenger
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That sounds correct it's not in front of me right now and it's been a while since it was done and one to 12v there are 4 wires off the relay
1977 Challenger
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Also do not forget to delete your ballast resistor if you are still running one
1977 Challenger
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I wish I had a diagram that shows the ign switch, HEI, back of the engine harness, relays and solenoids to add, gauge of wires to use.
I have seen a bunch of stuff on google images, but nothing that is close to what i'm trying to do and make me feel confidant.
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I will try to get some better pictures of mine today for you to see when I get home
1977 Challenger
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Cool 8)
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Ok so here is how my 460 HEI is wired . Wire from ignition switch comes into the electrical block. From the back of the electrical block to the relay (smaller black wire). That leaves 3 wires on the relay. One runs to ground (white wire). One runs to to constant 12 v bat (yellow wire). Last wire runs to the lead on the HEI distributor (blue wire). Then you have your tach wire runs directly to the other lead on the HEI distributor.
1977 Challenger
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They say that you only need 1 12v wire and a tach wire. You have what appears to be 4 wires.
How many 12v wires go to the HEI ?
Do you have a ground plugged in to the HEI ?
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Just two wires run to my HEI one from the tach and one from the relay supplying the 12 v to the distributor.
1977 Challenger
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The relay just ensures you have a constant 12 volts to the distributor. Your going to need to get a constant 12 volts to the relay and then you will use the ignition switch to "turn the relay on" and send the 12 volts to the distributor that's the reason for the 4 wires. Constant hot to power the relay (1) a ground for the relay (2) a wire to "turn the relay on" (3) and one to send it to the distributor (4).
1977 Challenger
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I see. Blue is 12v from relay and the red/pink is your tach, the other wires pictured in the distributor photo just go from the cap to the base, and then to the module I assume.
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Correct 👍 sorry I am sure I could have explained it different but you got it now.
1977 Challenger
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Do you know what gauge is for the colors you used?
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I think it's 14...
1977 Challenger
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What about a part number for the relay or the size of amp?
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It looks like the black is smallest, blue and yellow are a little bigger and then the white kind of looks bigger than all.
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Here is the relay
1977 Challenger
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The black is smaller it just powers on the relay the others are the same size
1977 Challenger
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The bigger wires look to be 10 or 12 gauge.
Thanks for everything. I think I got a good handle of this.
I did read were some put a 30 amp fuse on the batt wire befor the relay.
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You could be right on the wire size I really can't remember it could be 12 but I don't think it's 10. Any cheap relay will work. You can certainly run a fuse if you want for added protection but the relay will also burn out just like a fuse for protection also but it would maybe save the relay should something happen
1977 Challenger
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Probably overstepping, but maybe a description of what a relay does will help.
A relay is composed of a normally open switch and a solenoid that operates that switch.
The switch part of the relay is wired to your 12v source (in this case your battery) on one side, and the component you are powering ( in this case your hei dist.) on the other. The solenoid, which operates the switch is wired to the ign. terminal on your ignition switch. The ground wire on a relay is for the solenoid part of the relay. The basic idea here is that with a relay, you are indirectly powering your hei from your ignition switch. When 12v is applied to the solenoid it closes switch which allows the 12v from your battery to power the hei. That way, your hei gets 12v from a short run of wire from you battery which avoids voltage loss caused by the resistance that accompanies a long run of wire (I.e.: from the battery to your ignition switch and back). The solenoid part of the relay draws very little current so that voltage loss is not critical, hence the gauge of wire from the ign. terminal of your ignition switch does not have to be that heavy (14ga. would be sufficient. )
Hope this helps.
Apologies if you already know this stuff....
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Probably overstepping, but maybe a description of what a relay does will help.
A relay is composed of a normally open switch and a solenoid that operates that switch.
The switch part of the relay is wired to your 12v source (in this case your battery) on one side, and the component you are powering ( in this case your hei dist.) on the other. The solenoid, which operates the switch is wired to the ign. terminal on your ignition switch. The ground wire on a relay is for the solenoid part of the relay. The basic idea here is that with a relay, you are indirectly powering your hei from your ignition switch. When 12v is applied to the solenoid it closes switch which allows the 12v from your battery to power the hei. That way, your hei gets 12v from a short run of wire from you battery which avoids voltage loss caused by the resistance that accompanies a long run of wire (I.e.: from the battery to your ignition switch and back). The solenoid part of the relay draws very little current so that voltage loss is not critical, hence the gauge of wire from the ign. terminal of your ignition switch does not have to be that heavy (14-16 ga. Would be sufficient.)
Hope this helps.
Apologies if you already know this stuff....
Correct. I think you are saying the same thing as was said above just in a different way...smaller wire just powers on the relay sending 12 volts to the distributor... The other wires are simply a ground, 12 v in and 12v out... By using the ignition switch to turn the relay on you are simply allowing the 12 v to flow through the relay to the distributor.
The relay keeps you from running 12 v all the way to the dash through the switch and all the way back to the electrical block and to the distributor. Thus little to no drop in voltage to the distributor using the relay.
As long as you switch is in the run position the relay will allow a full 12 v to the distributor once running thus not burning out your module either.
One other point, I did have to replace my ignition wire from the switch. Before adding HEI I had no issues starting the 460 with the old points style ignition. However once I added the HEI and got everything wired the 460 would just crank and crank not fire I had quite a bit of voltage loss with the old wire. The new wire resolved this instantly so the relay does require at least a decent amount of voltage to trigger on.
1977 Challenger
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Just a thought, Is there a marine or coast gaurd approved relay for the closed engine compartment? I would assume there is a spark taking place when activated?
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Not to my knowledge. Any relay is completely enclosed not allowing any "spark" to escape.
1977 Challenger