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Hagerty Employee

What I learned from testing the limits of an “idiot-proof” design

After my Austin-Healey's BMC A-series engine had left me stranded two times in as many weeks, I discovered that the points were more charred than a well-done steak at Golden Corral. So I sat down and ordered some parts and prepared myself for the task of playing with the ignition timing. That meant reading every manual I could find—I even dove into YouTube and absorbed everything I could regarding how to properly set up a new distributor.


I know what you are thinking, dear reader: Why is he replacing the entire distributor when all he needs is a set of points? Also, didn't Rob Siegel talk about this like two weeks ago? You are correct on both fronts, but hear me out. This article isn't an explanation of my choice to upgrade to an electronic distributor, or the exact how and why of the install. No, these are my thoughts about a word I used to describe the design of the BMC A-series distributor drive—“idiot-proof—and how it came back to bite me.


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Advanced Driver

I realized years ago, & it's true for myself also, that when somebody is referred to as an Expert or Experienced in whatever, it basically means "I won't make that mistake again" 

Pit Crew

As I have said for many years, "If you try to build an idiot-proof system, the universe will inevitably build a better idiot."


I'd love to say I haven't done the same thing, or on a less idiot proof design (American motors), stabbed it on a tooth off, and wondered why it ran poorly, or forget to hook up a wire inside the distributor in an old Bentley that requires an afternoon to get to again.. Or a million and one other dumb things.


Only points system you can't screw up is the one on my 2CV. Literally. Impossible if you hook up the wires. Oh, wait, I did that didn't I.... 🙂 

Pit Crew

Nothing is foolproof, as Fools are so ingenious...

Pit Crew

Had the distributor of my MGA replaced with a Pertronix unit before the Amelia Island or Bust tour in late February of 2020. I had quite a few problems, especially when it came to running at moderate revs under a light load. If I ran the car harder it did a bit better. I never liked it, though and when it came out when I got home I just benched it. It was not money well-spent and I won't do that again. 


I am experiencing a similar situation, and I think the cause is the vacuum advance. I have it blocked off now and will log a few miles to see if it smooths out.

The saying at IBM is that you can idiot-proof anything, but you can't user-proof it.


Now that is a saying I will repeat!
New Driver

I routinely see idiots driving around in the pitch dark with their lights off. They are driving newer vehicles that have an "Auto Mode" option for the lights, but for some reason they don't use it or are too much of an idiot to even know what it does. 

New Driver

Or someone else got in the car and switched the lights from auto to off - as the guy doing my last inspection did for no reason at all.
Pit Crew

The one area I have learned never to touch on my '68 Cutlass is the ignition and especially the points, after long and painful experience of trying to service them always ended in failure. It amazes me how something that was in use for decades can be so troublesome (to me) and so intimidating. This is from someone who removed a GM HEI distributor to replace a failed internal part and then reinstalled it with no difficulty whatsoever after the engine started on the first try. Just keep me away from a points ignition.


Think twice (maybe 3 times) do once! Duh.

Advanced Driver

I say again--an Electronic Ignition is NOT fool-proof!  Everything will fail sooner or later.

Marketers are selling a product.  If you believe them, they are selling THE product which never will fail.  And, they are laughing their way to the bank!  With YOUR money!


I can't say I've ever seen an ad where any ignition system is being sold as "never failing." Marketed as an upgrade for various reasons, sure, but never "failure proof."
Intermediate Driver

I've been an idiot too. You're never alone if you're an idiot.


Working in the automotive industry, idiot resistant is the best we can do...

Pit Crew

Nothing can be made idiot-proof because idiots are so resourceful.


These well marketed electronic systems can and do fail as well as producing erratic timing throughout the RPM range. Send your points distributor out and have it rebuilt NOW and carry it with you. You're gonna need it.


To be fair, everything fails. There is no perfect design. There is some designs better suited for certain situations though, and I feel this setup is ideal for this car.

I've never understood the fear of  ignition points . Nothing could be simpler to set or repair for the home mechanic. When electronic components go bad there is little you can do yourself other than replace parts. I always keep points on old cars with very little in the way of problems.




All things considered, Kyle, it was a pretty minor mistake, and even at that you had a 50-50 shot at being right. At least you didn't head off on some unrelated tangent, and you correctly assumed that the problem was likely to be the last thing messed with.

Pit Crew

The first clue is that it is a British car. Back then they baked issues into the car. Then the author just was not thinking. Fools are so ingenious that is why nothing is foolproof.


If everything was "idiot proof" it would take all the effort / eventure / fun out of it. I have a perfectly running 83 F body, runs and drives great however, an LS swap (technology upgrade) would REALLY make it come to life, and some tires to death, so it's worth the trade off. Keep on wrenching -


Put finger over the spark plug hole and hand crank engine until pressure pushes your finger off the hole, now you are on compression stroke and valves are closed.

New Driver

My first car in 1974 was a 1968 Sprite MKIV 1275 very much like yours, and it was once side-lined for weeks if not months by my reinstalling my points with the little looped insulating washer in the wrong position. After much frustration and head scratching, I had my eureka moment and figured it out. 


Now 46 years later I have another 1275 Sprite that has been perking along for three years with almost no attention to the points!

Pit Crew

Made that mistake on the first engine I rebuilt ('64 Rambler L-head, in 1986).  Very disheartened when all it did was cough and backfire when I tried to start it.  But felt great when I and my then-very limited skills were able to figure it out.  Today, I'd feel like an idiot. Back then, it was a learning experience. 

Intermediate Driver

Actually most manufacturing uses the japanese method of poka yoke to try and idiot proof the assembly process because putting a distributor in the wrong way means some repairman will have to correct the mistake latter on in the process causing added expense to the finished product and that is the driving reason to get the job done right the first time by anyone with minimal training.

Pit Crew

How in the world did you leave the points in there so long without ever checking or replacing them?! Isn't that one of the first things one might do on picking up an old car? As for Pertronix, don't feel so secure. These are NOT as robust as OEM electronic ignition systems. I have one quit after 24 years of service, and two last about a summer. Always carry a points and condenser set and an "idiot proof" drawing of how to sawp them back in for the day your Spridget mysteriously stops dead and refuses to start.


I bought the car 4 months ago. I firmly believe in the theory that if it ain't broke, don't fix it. It started and ran smooth when I handed over the cash and signed the title. No reason to immediately start spending money replacing items that weren't worn out.

From my manufacturing background in engineering and design the term "idiot proof" has been discarded long long ago. The idea of  proper assembly on the line is paramount of course. Idiot proof term can only have one meaning and its very degrading to the assembly line worker or any other part handlers. Its ancient meaning has no place in most professionl environments anymore,   "Poka-yoke" meaning fail safe is usually the term used as substitute.  Your editors should of caught this one. In any event, the author made a human mistake. Take care. Sincerely, Sigmund


I believe the statement below is the Murphy's Law corollary "Make something idiot proof and Nature will make a better Idiot"; or something thereabouts".   Now all of us, that work on old cars etc and that can admit our failures, have made that mistake.  Some of us twice.  🙂  Either by putting the distributor back in 180 degrees out or not paying attention to TDC "fire" number 1, and messing up the wiring.  Sometimes it happens because the last guy didn't take the time to put the number 1 spot on the cap where the factory indicated it should go. 


So, we come along and don't pay attention to where number 1 was and put it where the book says it should go and can't get the engine to time correctly or possibly even run at all.  Now it's more fun when you're the guy called in to figure it out.  🙂 


Then you can give the situation the thorough glance, then look like a man f great sage Wisdom and point out that the distributor is in 180 out, or point out a previous mechanic has just put # 1 in the wrong place when compared opt the 'normal' placement.  Then you can go on espousing great wisdom and historical facts to help the younger and uninitiated.  🙂


It's a bit like when you were the new guy, at the Service Station and the old guys told you to get the wheels off that old Pontiac or Mopar and didn't tell you about left handed studs on the Driver's side of the car.  So you just turn the gun up stronger and eventually break a wheel stud.  Then you break a second one.  The you go into the other room and find the 'old' guys laughing at your misery.  🙂  They explain how some older cars had left hand thread studs on one side.  You get to call the parts store and order new studs.


Then later, when you're the 'old hand' you get to have the same fun and get to offer the same wisdom to the 'new guy' months or years later.  🙂 It's a bit of an initiation, really.




"Had the distributor of my MGA replaced with a Pertronix unit before the Amelia Island or Bust tour in late February of 2020. I had quite a few problems, especially when it came to running at moderate revs under a light load. If I ran the car harder it did a bit better. I never liked it, though and when it came out when I got home I just benched it. It was not money well-spent and I won't do that again."


I had the same problem with a Petronix distributor until I realized that I wasn't running at a full 12v. Most points systems don't. That is, most don't once you start it. The cranking circuit usually operates at a full 12v, but then once in the run position either run off of a ballast resistor, or in my case a resistor wire that as the car runs increases resistance while decreasing voltage to 6v. If you don't either bypass the ballast resistor, or resistor wire, they will run great at first but degrade rather quickly. This is why most people will experience it running great right after start, then slowly the performance will erode until it won't stay running at an idle, but will run great wide open under high revs. 


Unfortunately, that little tidbit of information is at the back of the installation manual. 

Intermediate Driver

Making something idiot-proof just challenges the idiots.

Intermediate Driver

As soon as you said idiot proof and only goes in one way, I knew you were in trouble. Simpler than the gear drive, but still a 50 50 deal at best.

Those of us who grew up with points knew a match book cover can substitute for a feeler gauge. And you set the dwell before the timing.

At times I have debated upgrading from the dual point on my old Pontiac to HEI, but I know what’s in there is not stock, and recurved. So although electronic would be nice, finding someone to recurve it would be a hassle. 
Carbs are another mystery for some. Idle speed and screws are just the tip of the iceberg if you really want to dial one in.
A buddy had a model T when I was visiting that wasn’t running right. All I needed was for him to tell me I could adjust it while he drove. What a difference. I just wonder how many drivers were killed trying to drive and adjust the carb themselves. 
Engines need the same basic things to run right - whether a model T or a newer model with a computer. If you understand the old stuff, tuning with a laptop is not a complete mystery. Just your toolbox changes.
So when you have valve adjustments, are you using the harmonic balancer? Or when the intake just closes, adjust the exhaust, and when the exhaust just closes, adjust the intake? If you are real good, you only need to rotate the crank twice. 
My teacher was an engine builder. A hydraulic cam can be adjusted as basically a zero lash solid lifter cam for racing. Nice little trick to get a bit more out of your motor and if your started to get clatter, you knew you had some wear to look into.


New Driver

The engine was OUT OF THE CAR!  Why didn't you determine and mark TDC on the crank pulley?  You know, pop the valve cover and watch the valves ... and adjust the lash while you're in there.  It only takes a few minutes for all that.  Oh, and mark the wires at the spark plug boot, unless you change them when you replace the disti.  In that case, mark the new ones.  It only costs a few points at Concours, and if that blue Healey in the picture was yours, it didn't belong at Concours.

Darn, I am showing my age -- I learned how to adjust points and time a disti by ear, then tweak the dwell for max power.  And almost 30 years ago I saw a very prescient comment by a Jag mechanic who said "DON'T tune by the book.  That's only good for cars fresh out of the factory.  Tune the car, not the manual."

And ... always know what parts to keep in the glove compartment, like 1157 bulbs, an ignition module for any GM with HEI, and a spare car for anything made by Ford.


I did align the timing mark on the balancer, but that doesn't mean the number one cylinder is on TDC. That was my error, as I admitted in the article. I didn't want to take the rocker cover off initially because (miraculously) didn't leak and I didn't order a replacement gasket.

As an "Olde Brit" mechanic, and if my memory serves me correctly.  The rule of thumb for re-installing the distributor correctly(providing the drive is in the right place) is to point the rotor at the #1 plug.

New Driver

I have had two of your new distributors that failed.


How many new cars do you see driving at night with "Daytime running lights" on and absolutely no tail lights? Also making a mistake doesn't make you an idiot, it makes you human, making the same mistake again after knowing about it does boarder in idiot territory.

Pit Crew

The same thing happened to me the first time I replaced a distributor after rebuilding it. Couldn't figure it out because of course I thought I had did something wrong in the distributor itself. Fortunately an old "real" mechanic friend stopped by took one look  said "180 out dummy" and fixed it in about 5 minutes. Trick he taught me which is "fool" proof was to use a compression gauge on the number one cylinder so you know that it is on the compression stroke and where that plug wire belongs on the distributor in alignment with the rotor.

Intermediate Driver

Kyle, not to sound picky, but your car is really not a "Healey". That term is generally reserved for the big Healey's like 3000's, 100-4, and 100-6's.  What you have is a Sprite (or Spridget, since the A-H Sprite and MG Midget of those years are essentially the same car).


I say this having been a Sprite owner for many years, and knowing that the owners of big Healey's can be a little "protective" of the terminology.



Guy with the old Pontiac & real points is not as dumb as some might think, electronic is great when it works, when it fails, pull out the cell phone, you ain't goin' anywhere pal.  Points seldom fail, you can tell when you've traveled too far, usually over 13K, should have replaced 'em sooner ~    I've had to go rescue pals that converted, then wished they didn't ... left stranded too far from home. 

I replace 'em at about 10K, put the 'good' used in the little box with the spare coil and condenser, don't need a cell phone along.

Pit Crew

Gotta give credit for having the gonads for admitting this elementary error! 😂

Advanced Driver

Call me an admitted idiot. Driving old cars is probably idiotic but then again, my old cars require a bit of attention like checking the oil and warming up, you know things an idiot can do.  
 New cars require a manual to explain how to tune the radio,turn on the heater, unlock the doors, adjust the seats,etc.

 Old cars could be approached and reasoned through eventually, new cars must be troubleshot by computers it would not be possible to seat of the pants error code. 
 New cars can have the keys locked in by one false push of the wrong button. My Sprite couldn’t leave me that way cause there isn’t a door lock anyway. As an admitted idiot I will knowingly hop in to the Sprite with the top down knowing the temperature variations could be colder than 68 or warmer than 72 requiring extra clothing or resulting in sweat. A smart person would never accept that! 
 I spend hours watching the smart people angrily driving modern marvels too fast with zero connection to the world around. I feel a real connection to the other cheerful idiots driving automotive dinosaurs taking in the scenery and enjoying “the ride”.


I think all of us have "stabbed in" the dizzy and been out. The old Mopar design that was basically like a slotted screwdriver gave you a 50/50 chance of being in or 180 out. Guess how many times I was 180 out?


On points, I still keep a set on hand in case the Pertronix unit fails. But.....the quality of components you get these days is NOT an apples to apples comparison to the points sets of old.

Pit Crew

Howdy,I'm surprised you didn't just index the base of the distributor and look to see (under the distributor cap) where the rotor is pointing. The distributor drive on most Hondas is engineered the same way. Hopefully this helps next time around for you or someone else.

Where number one compression was wouldn't even come into play. Firing order is a whole different issue though.

Oh well, live and learn... Get 'em next time...



Pit Crew

This is one reason I like to work on my own cars - when there's a problem, I always know who to blame!


Pit Crew

There may not be any mechanical device that's 100% idiot proof, but speaking as a full fledged idiot, I can say 1960's Volvos come pretty close.  I was driving my 1965 122S to work one morning and the the engine didn't quit but the power output went to near zero.  I looked under the hood and found that the collar that holds the distributor in place had failed and the distributor had gone to full retard.  I tried advancing it and hoping it would stay in place but as soon as I started driving it went to full retard again.  This was pre-cell phone days and I thought if I walk home or walk to a pay phone and call a cab, I'll show up at work about noon my boss will not be pleased.  In desperation, I removed one of my shoe strings, tied it to a secondary terminal on the distributor, adjusted the timing to about where it was supposed to be and tied the other end of the shoestring somewhere on the engine.  I intended to do a permanent fix as soon as I got home, but with one thing and another I ended up leaving the shoestring on there for about a month before I finally got around to repairing the distributor locking collar.   

Hagerty Fan
Not applicable

The author was at #4 TDC compression instead of #1 which was at overlap, end of exhaust beginning of intake, both valves open at the same time. Next time with all spark plugs removed turn the crank over by hand with the tip of your finger over #1 hole until you feel compression then continue to turn the crank up to the BTDC # specified and install your dist. This way you don't have to pull the rocker cover off.