The Stovebolt Site Forums The Shop Area Engine Shop Points HEI....10ga. wire and My 81 yr. Uncle?

Hey to you all....well my uncle is ready for "us" to install "our" Langdon's mini HEI which I purchased two years ago but have not had the time to install with all the other stuff to do. "We" need to get rid of the firewall ceramic voltage reducer and use a 10ga. wire from the Ign. switch to the dizzy. Can "we" use standard stranded copper wire? Do we need to buy a different Ing. switch as we have the original which works and the system was switched to a 12V by the PO???? Also.. my 81 year old uncle says to use a vacuum gauge to set the dizzy and reduce that number by two pounds then hop in with a wrench and drive the truck up and down some hills and when it pings stop the truck loosen the dizzy and turn it CCW just a bit then do it all over again....has he lost his mind or is he pulling just my leg???? Why did man invent the timing light??????HELP....T/C Steve

You can set it with a timing light but if it still pings, you'll still need to back it off before any damage happens.

As far as powering up the distributor, be sure to fuse it some how, don't go directly to the switch,
Just my 2 cents,
Scott

The vacuum guage approach works and I suspect existed before timing lights were available. Remember the timing light approach is no more accurate than the timing marks. The vacuum guage approach is based on what works best.

Standard automotive type stranded wire is correct.

Is the ignition switch up to the load a 10 guage wire will support? You need something to protect the switch and wire whether its a fuse, circuit breaker or fusable link.

My 78 year-old uncle would probably love working with your uncle.

I used the stock ign wire to power a 30 amp relay, use a late model fuel pump relay from the junkyard, put a 30amp fuse from the battery and run it to the relay then to the hei. Hei's use a bunch of amps, AND, if you do this you have really not cut up your harness, AND your whole ignition system is easy to see, troubleshoot, ect. Just a thought,, oh yeah, 10ga is a must.

HEI draws about 4 amps running.I don't know where this 30 amp rating came from.

You can set it with a timing light if you like but the vacuum gage a good ear and some patience will work much better as OldSub said the vacuum gage method is based on what works. Also keep in mined that the fuel quality when these old trucks were made was not good so today the same truck could benefit from a little more advance in the timing.
You may want to get it where it runs best with the vacuum gage and ear then put the timing light on it and record the numbers for next time and wile you have the light on it if you have a tach you can also check the advance curve and know that it is good also, the timing light has it‘s place but first you must have good references without them it is merely a flashy thing.

I'm curious too. A #10 is good for almost 50 amps. This HEI is solid state and can't draw much. Is wire size anything more than current carrying capacity...I don't think so.

I have seen a #10 mentioned numerous times in regard to this system. What's the real poop.

Stuart

Hey Steve;
Sounds like it's finally going to be HEI time!! Good.

I just followed Langdon's very brief wiring diagram, ran a #10 from my stock switch to the new coil. It didn't make much sense to me to leave the #14 that fed the switch in so I also replaced that with a #10. I just went to our corner FLAPS and bought 8' of red #10 wire. Had a lot left over. The whole #10 thing seems to be way overkill to me but whatever.

I like the ping and twist method of setting final timing. Each engine seems to have it's own sweet spot and if it is set just below the ping point on hard acceleration, you'll be getting the best in performance, and economy. Only thing is, turn the dizzy CW (not CCW) to get rid of the ping. I do use a timing light to get it close before I start the final highly scientific fine-tune procedure. Good luck buddy!!

The big wire is for cold-start current capacity at low cranking speeds. A HEI unit can, and does draw up to 20 amps or more under certain situations. Check the resistance of a HEI coil sometime, and you'll find the primary winding is between 1/2 and 3/4 ohm. At a cranking voltage of 10 volts, and a slow trigger signal from the pickup coil to allow for full current flow in the primary, 20 amps or more is just basic Ohm's Law.

As speed increases, and the inductive reactance of the primary goes up, the primary current drops noticeably. The wire still has to be capable of "worst case" scenario capacity, however. Ditto for the ignition switch, and the battery wire that supplies the switch. On any vehicle that came out new with HEI, there will be a high-current wire supplying the switch, and very heavy contacts inside the ignition switch, also. The relay is a good idea, as long as it's a continuous-duty type with enough current capacity.
Jerry

OK...now I'm confused real good....can we / do we use an in-line fuse to the Ing. switch? My uncle says that it will blow when starting? I think I had better ask Mr. Langdon his products are first class but his web site stinks as far as installation instructions and is very technical also BUT he is always ready with an answer and is a great guy...he needs a Web designer. My uncle says all points only draw 6 volts thats why the ballast resistor on the firewall to take it from 12 to 6 and 6 volt electric systems do not need a ballast resistor....learn something everyday from him! Someone wrote on another forum that pinging can deystroy a 235 how long or how many times do we have before we wreck"our" engine if we mess up the timing? Thanks to you all for the continued help and T/C Steve and UNC

HRL,what gauge is the wire feeding the HEI from the ignition switch on a stock GM vehicle? Is it fused on a stock GM vehicle? Is it the 20 amp fuse labelled ignition and ECU,the supply for the HEI on GM vehicle I've seen?
I have a HEI on a 235 in my 53 truck.It's got a 15 amp Buss fuse,been that way for years.
Langdon says the big wire is to limit feedback or harmonics on the circuit.
An Amp meter inline on the HEI shows about 3 amps at idle,rising an amp or two with increase in RPM.I'll check it while cranking too.

...as my eyes glaze over...
I wonder why this thread isn't in Electrical.

Both the feed wire to the ignition switch, and the HEI hot lead on GM original equipment wiring is 10 gauge. The ignition switch is fed directly from the battery cable terminal at the starter through a fusible link, not a fuse, with a 50 amp rating, IIRC. It must carry the surge current of the starter solenoid pull-in winding (up to 30 amps) plus the load of the ignition system.

"All ignition systens work on 6 volts"- - - - -WRONG! Point-type ignition coils designed for 12 volt ignition systems require a ballast resistor to drop running voltage to approximately 9 volts. Why? Because there's a bypass circuit that delivers straight battery voltage to the coil during cranking, usually about 10 volts, and for the coil to work efficently on a cold start, it must be able to work at full output at 9 or 10 volts. After the engine starts and the charging system kicks in, voltage can be 13 to 15 volts, and a resistor is needed to prevent the coil from overpowering the points and burning them due to high primary current.

Solid-state ignition systems don't use points, so they can use full battery voltage and high current draw coils. That makes over 50,000 volts available to fire the spark plugs, instead of 20,000 volts or less from a point-type system.

If you're going to protect the circuit from the battery to the ignition switch, use a 40 or 50 amp circuit breaker, or a #10 fuse link, not a conventional fuse.
Jerry

Jerry.....my mistake my uncle said that the points only ever take up to 6 - 9 volts as 12 volts will cook them and that 6 volt systems never needed ballast resistors as the points only ever got 6-9 volts....you are most correct thanks for keeping me honest. OK...a number 10 fuse link to the Ign. switch Batt. side of switch?...Have we got it? I guess we can get one at the local Napa store....never seen one...... YES... I guess this is electrical stuff but it all has to do with removal and installation of a distributor so either forum could be right...that's my opinion and therefore it is correct! T/C Steve

HI.....Mr. Langdon responded to us by email is, "Steve no fuse is required, Tom." ......Well I guess the master has spoken. I hope this info. will help other people with the same questions as we had. Thanks to you all! Steve and Unc

I don't come by here much anymore but I saw this post and can throw in my two cents based on theory and my real life experience of adapting GM HEI's to at least 5 Chevy and GMC 6's
Being an electrican I can understand all this stuff at least in theory.An HEI coil is usually around .5 Ohms at the vehicle running voltage of a nominal 14 volts.Ohm's law says amps is volts divided by resistence,.5 Ohms in this case.So there's a potential in theory for the HEI coil to draw 28 amps.In reality it's less than 28 amps due to short time period the coil is allowed to "fill" with current between sparks.And I do believe the HEI module limts the current to the coil to prevent overloading.
A short run of #14 wire can conduct a steady flow of 20 amps with acceptable voltage loss,The National Electrical Code amperage flow for wire sizes doesn't apply to automotive use.
But the HEI current flow isn't steady,there's an inrush of current 100's of times a second depending on engine RPM's.Beside the current inrush,electrical flow isn't instantanous,there's a slight lag when more current is called for.A larger wire will help to overcome this.Kinda like a drag car taking off,it takes a brief second for all the forces to react.
So the 10 gauge wire is a safety factor so to speak,covers all bases.The large wire keeps voltage losses acceptable in a worst case senario.
In normal situations,like my low rpm truck engines not needing all there is to fire the plugs,a #14 or 12 wire is adequate from my personal experience .

Thanks for the help you made the information much more user friendly! T/C Steve

One more thing,personally I think it's bad practice not to fuse the feed from the ignition switch to the HEI on an old vehicle you have invested time and money into.In case the wire gets shorted somehow,it'll save your wiring harness.My truck has a 20 amp circuit breaker feeding the ignition switch protecting the whole switch from shorts or overcurrent.I have no ignition switched items other than the HEI and a single small electric wiper motor.And in 10 years the circuit breaker has never tripped from the HEI load and or occasional wiper use.
Use a circuit breaker,the ones that plug into a fuse holder are only a few bucks.A 30 amp one will at least not nuisance trip and will trip from a dead short.
Here's some info off the internet,you be the judge if it's totally accurate,shows amp draw etc.
HEI current draw and rpm

Got the 30 amp info off a website, ANY voltage drop would be bad for a hot spark, so 10ga isp p robablyp advisable, Why do they use 12ga on the stock gm harnesses? Someone with a new aftermarket harness look at theirs so the sharpshooters can be SURE that no one "overwires" anything.