The Stovebolt Site Forums The Shop Area The Electrical Bay Installation of HEI distributor

I bought a lightly used Tom Langdon HEI distributor from a fellow ‘bolter and I’m in the planning phase of installation. It needs a 10 gauge supply to the coil taken from the ignition switch. The current wire going to the coil is only 14 gauge. Is the switch able to handle the additional current, or should I add a relay?

Phil I had this same situation...plus I have an electric fan (which I installed initially on a Bosch-style relay). The switch I had failed so I went with a 30 amp switch and also a Bosch-style relay on the Langdon distributor. One of the problems I had when the ignition switch was failing was you could start the engine but you couldn't stop it. You could turn the key to off, but it made no difference. One of these days I'm going to take that switch apart and see what happened in there. The switch I bought was what looked like an exact copy of the old Standard Parts switch and it fit just fine...made in Taiwan as I recall.

No relay is needed.

So the original switch is adequate for the additional draw?

Don't bet on it- - - -The surge current when the power transistor in the module turns on, before the inductive reactance of the coil primary windings kick in can be 20 amps or more- - - -several times a second. While it might be technically possible to run without a relay, anyone with a few brain cells to rub together would probably choose to err on the side of caution and run the relay. I like to use a 60 amp Bosh style relay, not because its current capacity is needed, but the wire gauge of the adapter plug that's sold with the relay is much heavier on the 60 amp relay. They're dirt cheap on Ebay. I usually keep several of them on hand. PM me with a snail mail address if you want, and I'll send you one.
Jerry

The problem is the surge (saturation surge) when you first turn on the key to start it, Phil...not when the coil is replenished between cylinder firing. That first surge is slow and allows the coil to absorb a lot of current but replenishment timing is in terms of apx 2.5~4mS or less depending on your rpms and during that sequence the coil isn't using as much amperage. It can't, actually. There isn't enough time between the on/off pulses for the coil to saturate as it will on startup. Just like in the points system it (the coil) is going from 0 to whatever it can build rapidly. However the HEI module can draw at least 20 (or more) amps when the coil first switches on (when you start the engine) and that's what will ruin your ignition switch (if the distributor/coil is not on a relay). I have the Langdon mini-hei too, by the way. Depending on the coil used, draw at idle runs about 3 to 4 amps and this will decline as your rpms increase (due entirely to the reduction in time of the pulses). The startup surge is what will fry your 10 or 20 amp rated ignition switch. It may not do it right away, either. As I recall mine took a couple of weeks to croak.

Sorry Jerry...I evidently type a lot slower than you...

Yep, sometimes my fingertips smoke- - - -I keep a vat of icewater handy to cool them off! If I ever learn to touch type, look out! Real GM ignition modules have a built-in current limiter that kicks in as the coil primary reaches full saturation. That's one circuit that aftermarket modules eliminate as a cost-cutting measure. That cheap no-name ignition module that's sold online from a lot of vendors is no bargain!
Jerry

Langdon's HEI uses a remote coil with no current limiter...I think it was a GM product, though.

GM's current limiter is built into the module, not the coil. As the primary winding approaches full saturation, the current control is visible on an oscilloscope waveform of the primary ignition circuit as a squared-off step-down of the sweep. It's not there on most non-GM modules.
Jerry

Below is the old Standard Products switch that failed. This switch was made for NAPA, Sears, Ward's, Western Auto, White's Auto, Gibson's, K-Mart and just about anyone else that wanted to sell an ignition switch under their own label from the 60s up into the mid 1980s. The URIAH copy is exact except that it is marked Taiwan instead of USA and the contacts are rated for 30 amp. Even uses the same key blank. I got it from Amazon about 3 years ago. Some cold winter's day I'll disassemble that Standard Products switch and we'll see what happened inside to cause it to fail. Not today.

Langdon instructions do not say relay is needed. The switch has adequate contacts. It's a simple rotary switch with big copper contacts. Most likely any failure will be Mechanical, which a relay will not help.

When I first installed my Langdon hei I did not use a relay on the new 10ga wire, voltmeter showed a bit erratic voltage at the Hei coil which I mounter on the inner fender. The ignition switch on my 46 controls the starter ( no stomp pedal) so the source /quality of the switch is unknown since I did not set this up.

With the new dizzy I was chasing a significant part throttle studder with the new Hei, At that point I chose to run a 10ga wire from starter to/install a 70a capacity continuous use rated 12vdc relay I sourced from local NAPA under the dash and the voltage became very stable. Also per HRL I grounded the generator to the regulator just to eliminate the possibility of issues there. Checked for vacuum leaks, tried new fuel, timing here timing there, blah blah blah…

It did not solve the studder, reinstalled the old dizzy to confirm nothing else was the issue and the engine still ran fine, I then reinstalled the Hei (and needing to try something) sourced & installed a NOS Delco spark module in the Hei dizzy, studder was gone and the truck is running better than ever 3 months on….
I post this only to show that seemingly simple parts changes can go sideways, so be patient, and methodical.

Oh, and get a programmable advance timing light (also per HRL), you need 12-18 advance and there are no marks for that….for my 54 235 it is set at flywheel BB + 9 degrees.
Good luck.
Chuck

Chuck isn't that GM spark relay about the same as the Bosch type relay? The last one I saw was.

You needed 12 to 18 degrees advance on the timing?

Jon, I believe he's referring to the HEI distributor module, not some type of power relay. There's a noticeable difference in the internal electronics of the OEM module, compared to aftermarket ones, particularly the ones made in some third world sweatshop.
Jerry

Jerry is correct, the acdelco D1959 module, the one inside the dizzy (I corrected this in prev post)

Langdon instructs timing 10-18 Advance, .060 spark plug gap

Tom Langdon provided ‘new in pkg’ coil, plug wires and plugs for his setup.

I am a proponent of getting a proven combination of parts, plus Tom’s prices were very very fair, plus Tom is a real gentleman to deal with.

Chuck

Thanks all for your input. The coil I have is the round type (ford), and the terminals are not threaded.The distributor has ring style connectors. I emailed Tom about the situation and he asked me to give him a call. I’m going to pose that question (powering from switch) to him. I’ll post his recommendations.

Getting an HEI to work at its best requires full 12 volts which requires looking at the entire power and switch arrangement to assess wheter you can reliably power the HEI from the ignition switch. If the ignition switch receives its battery power via anything less then a 10 guage wire, you are probably making a mistake powering the HEI from the switch. If the switch receives battery power via 10 guage wire, then you have to decide if you can run a 10 guage wire from the switch in the first instance, and whether there are other loads being pulled from that side of the switch. If so, then you will liekly over load the swithc and cause either a failure or melted components.

Using a relay is not perfect, but it does eliminate a lot of issues for the HEI, particularily if the relay is pretty close to the battery or starter and the HEI. The relay is triggered by the ignition switch, and the relay powers the HEI with a full 12 volts, without any voltage drop from long wires, switches. Its not a terrible way to do it with old, older, vintage or even reproduction stock wiring, at least in my view, and I have used a relay to power a HEI on a couple of occasions just for those reasons. It works really well and to me, just a safer way to go about it if your electrical system is less then ideal.

I just spoke to Tom Langdon, for more than a a half an hour and talked about allot more than the distributor, including upgrading my brakes and drive train. Real nice guy really interested in our trucks.

He advised me not to use a relay. He said, it’s not needed and is just one more component that can go wrong. He said the coil only uses about 4 amps when running and the original switch is rugged enough to handle the initial load.

I also found out about the round (ford) coil that I have, and he also advised me not to use. He suggested using square GM coil he sells on his site. He said he had too many issues with the round coil that he stopped selling it. He also said that that was why Ford discontinued using it.

He assembled an installation kit for me, complete with the new square coil, hold down clamp, connectors, plugs, everything needed for my installation plus instructions for 31 dollars plus shipping! Couldn’t go wrong!

I'm thinking of an HEI for my '55 235.
I'm confused.
If I get one, what amp relay do I get?
Does it go between coil and ignition switch?
I plan to install a new coil as well.
Are those knock off HEI kits on Ebay any good?

If you are willing to replace ALL the electronic components on the offshore HEI, you'll be almost as good as an OEM GM unit. That includes removing the gear and shaft and installing an original pickup coil. The offshore ones are junk- - - -no discussion needed. Use a Bosch style 60 amp relay. No, you don't need that much relay capacity, but the wire gauge of the plug that's supplied with it is more suitable for the HEI distributor. Run a power wire from the battery cable at the starter, the back of the alternator, or some other source of full battery current to the relay. Just use the ignition switch to turn the relay on and off. That assures that the HEI module gets enough voltage and current to operate properly. Overkill on current capacity is never a bad thing, no matter what the self-appointed "experts" claim. The system will consume whatever current it needs- - - -no more or less, unless the supply circuit is too puny to carry the load.
Jerry

DonBolt,
There is only one solution for your HEI. Langdon. Unless you want to BUILD one yourself or go with Pertronix. As you can plainly read on this thread, Langdon says NO relay and use his coil and 10 ga wire. Don't over think this.

The original question was about a relay being used to protect the ignition switch. I answered that question TWICE on 24Aug22. I contacted Langdon on 25Aug22 to confirm a few things. One was about GM (and Langdon) saying 10 ga wire needed. The other was about the ignition switch. Answer came back 26Aug22.

1. QUOTE: 10 ga wire........... GM says....."is intended to prevent false triggering of the module under certain conditions."
2. QUOTE: Relay to protect switch........"The stock switch is O.K."

The email was signed Tom Langdon

Interesting topic. Pretty disparate opinions from smart people I trust.

Tom Langdon doesn’t think the relay is NECESSARY. But did he mention any real downside? Other than it’s just one more part to fail?

The “one more part to fail” is a common beef with relays in general.

(I don’t know enough to have an opinion. Just soaking it in)

Not necessary from me or Langdon means you don't need it, but you can use one if you think it is necessary. Sometimes when something is NOT necessary it can cause or not cause an issue or be an extra part to fail.
Sometimes people do something when there is no problem. I'm not aware of anyone having a problem with HEI and a relay fixed it. I have already explained why it's not necessary for a USA original ignition switch or a Chinese clone built with the same internals. I am unaware of ignition switch failures due to anything but wear and corrosion. I have taken them apart and observed the contacts and the general construction with a my electrical connector/switch/contact design experience. What else can I say. It's always "here is one persons opinion/answer to a question, it's your truck do what you want". Not a big deal. Just bytes for your memory.

The Langdon HEI draws 5 amps max.
A radio or heater is maybe 10 amps/15 amps/20 amps

An ammeter won't burn up a truck
An ignition switch won't overload and burn up
Pigs don't fly
There is always someone who has seen one or more of the above

Just an aside, when I purchased my Langdon HEI Tom said he was out of core dizzys and didn’t know if he would get more, his words: “i worked from east coast to west and am running out”….
If you go to his website since then it now says sold out…….

As to the relay… I did it because I was chasing a problem, and the quality of my ignition switch is unknown (I don’t have a stomp starter so my ign switch is not stock to my 46).
In my case I would much rather have to jump the (plug & play) relay than attempt to jump at the ignition switch or Hotwire the coil.
Chuck

I built a Langdon-style small cap HEI from an offshore clone. It's a LOT of work! IMHO, it's not worth the effort when a regular stovebolt distributor can be converted to the same trigger system as the big cap HEI with a little bit of machining.
Jerry

If you don't want to do it yourself, call David Ray. He's been doing conversions for 40 years.


DAVE's small-body HEIs Converts your original points style distributor to HEI system
24 Buffalo Lane
Yerington, Nevada, 89447
775- 722-3294
[email protected]
http://www.davessmallbodyheis.com/

OUCH! Looks like the option is points I see a bunch of ideas for the DIY'er to modify this or that. Pertronix is probably jumping up and down now that Langdon is Out of Stock. Bummer. The are also some new dizzys. I can't find too mush positive on those. Everybody is selling JM6516BK. I think I traced these down to Australia. Red or Black. Can't remember.

Dave Ray also has a similar message posted on his website. No rebuildable cores to convert available.

So what dizzy is the core?

1981-82 Chevy 2.8 Liter V6 with centrifugal and vacuum advance. 83-up is electronic advance only. The housing has to be shortened, a lower bushing must be installed, and the drive gear has to be changed.
Jerry

From the early 80’s S-10 V6 engine, Jerry posted while I was typing

Here's the offshore-made clone. The drive gear, oil pump drive, and housing height have to be altered, and the electronics suck.

www.ebay.com/itm/124296539658?

Jerry

I'm asking what Langdon used, did he use the S10? Some guys seem to be using a 250

Yes- - - -the 2.8 S-10. The 250 used the big cap HEI.

He'll convert any dizzy you send him to HEI.

Thank you bolters!
I've had my truck almost a year and one by one I'm going through things that I want to change.
You've answered my distributor question with some great ideas and resources. Also noted not to consider a "kit from Ebay".
Don

Langdon?
Been running his unit in a 235 now 261. Best modification I've made, even better than T5!

To wrap up this thread, I installed the Tom Langdon HEI distributor this afternoon. I decided on using a Bosch relay for two reasons. I already have ignition power at the ballast resister mounted on the firewall just above the starter. Additionally I do not know the condition of my ignition switch so running high amperage to the switch seemed questionable, so the relay the better choice.

Installation with relatively well. I had previously created a harness for the relay, so it basically came down to exchanging the parts. After installing all of the components, a quick check insuring I had 12 volt power at the coil and she started right up. I attached my timing light and quickly discovered it was near impossible timing the engine without an advance timing light. I settled for timing it by ear until I buy one.

The engine sounds great and I can’t wait for a road test in a day or two, weather permitting! I do live in upstate New York, in the mountains and they are predicting snow!

If your interested in the issues I ran into as well as the installation, I wrote it up in my “Project Journal”. Here is a [LINK].

Phak 1 Wow tremendous discussion on HEI's,Langdon,offshore,my 5 all homemade used the gear it came with,never even heard of using a relay and sure didn't think it would take a charging system cable to power it ! All will fire-up and go like they have for years now. On AD ignition switch 71 yrs. old.