Technical what's the best ignition coil to buy? or does it make any difference?

Couldn't start Clarence the other day. Checked several things and in the end found there was no spark. I have a 322 nailhead stored WAAAAAY back in the corner under LOTS of stuff. It had a coil on it and none of my other spare engines had one. This engine hasn't been started in who knows how many decades. So I crawled back under there and removed the coil. Installed it on the 350 sbc in Clarence and it started right up.

OK; so I need a new coil.

• should I order a specific one?
• should I just go to the parts house and get whatever they have on the shelf?
• should I go to the parts house and request a specific coil?
• should I just keep running the (very old) nailhead coil?
• is there any advice you all have for me?

There are lots of threads on here regarding coils but none that I found answered any of my questions.

 

Depends if you have a pertronics electronic ignition, then use their coil. If points do you have a ballast resistor? Does your bad coil say internal ballast resistor?

 

Distributor is oem GM points type; probably Delco, but I'd have to go look.

 

I'll have to look next time I'm out there. At my age I have to look to see 'cause I probably won't remember. I don't remember a ballast resister though.

 

Bosch is your best bet

 

Ignition coils ehh? Don’t get me started. He he.

 

I've been running an Echlin IC12. GM ran this oil cooled coil on everything for many, many years. That's probably what you took off the Buick engine.

 

Is this an internal resistor or does it require an outside one?

 

Discounting quality differences, there's little electrical difference in most ignition coils. Coil primary resistance is important to avoid burning the points or overloading some electronic modules. A 1.5 Ohm primary coil @12V will generally require a ballast resistor, a 3 Ohm won't, that's simply to limit current flow in the circuit.

When guys talk about '12V' and '6V' coils, what they're really talking about is the coil primary resistance. A 1.5 Ohm coil would be considered as a 6V coil, the ballast resistor simply reduces the input voltage (and current used) to 6V when used on 12V.

 

I believe it requires an external resistor when run in a point system. I've got a small body HEI (external coil) and no resistor is required.

 

@Crazy Steve,

• You mention 1.5 Ohm and 3 Ohm values
• Are these inherent properties of a given coil?
• How do you know (or determine) the value of the coil you've got in your hand?

 

Turn the old coil upside down and read the part no. If it ends or starts with an "R", and was working on the existing engine, replace with any coil that says "use with external resistor". If there is no R in the part no., replace with any 12volt coil. There is more mumbo-jumbo out there about coils than nitrogen filled tyres.

 

Thanx man. That sounds simple enough.

 

Ohm meter across the + and - shows the resistance. If the coil you have on there (old Nailhead coil) is the right ohms then run it. New coils kinda suck, I've been hoarding old NORS Standard Ignition and Napa (made in the USA) and older Bosch blue made in Germany, Spain or Brazil. I even have a couple of Andover coils that Bubba used to sell, made in the USA before the company was sold.

https://ratwell.com/technical/BlueCoil.html

My .02

 

IF CORRECT!

Ben

 

Don't get hung up on those specific values, those are given as 'typical'. You can see variations of up to .3 of an Ohm plus or minus in the primary resistance of any given coil depending on how its wound. There really isn't any such thing as a '6V' or '12V' coil, that's simply a descriptor for recommended use in some cases. And there is actually two functions to using a ballast resistor; one to extend point life, and the other is to prevent coil overheating at slower engine speeds. Really, all your trying to do is reduce current flow to a 'safe' value so the parts will live longer. So a good guideline would be if running a 6V system, keep your coil primary resistance plus any ballast resistor value (if any) to well under 2 Ohms total to ensure a full spark. 12V, increase the total resistance of the two added together to 'about' 3 Ohms. This is true for any points system and many 'less featured' electronic ignitions. I'll note here if you have a race car that sees very little low RPM use, the majority is at wide-open throttle, you can delete the ballast resistor. If it's a street/strip car, you could get tricky and install a simple toggle switch to bypass the ballast resistor right before you make a run, switch it back into the circuit for 'normal' driving.

Get into the 'better' electronic ignitions and a lot of this is no longer true. Things like dwell control, current limiting circuits, more robust switching components, and/or multiple spark discharge can eliminate the need for a ballast resistor. Depending on the system, you may or may not need a 'special' coil. My personal 'go to' ignition is MSD as their system allows use of almost any coil without a ballast resistor while delivering full spark.

NO ignition system adds power to an engine, a properly functioning one simply allows you to get as much as is available. If you do gain power with a swap, that's telling you whatever you had was inadequate...

 

I would add another function of the ballast resistor. That is to aid starting through the bypass circuit when cranking. If not for that, I'd just run a '12v' coil, but that means my ignition would not be provided full 12v during cranking, especially on really cold starts. I once had a 413 that was transplanted into a 58 Dodge. Due to an error the installation it had no bypass. On mornings in the teens it always had to be jumped. Installed a proper bypass circuit and no more problems.

 

I’ve had lots of success buying ignition parts from The Brillman Company in Virginia. They have good, USA made parts and cheaper parts too. When you call, ask to speak to Mr.

 

@Truckdoctor Andy,

Speak to ????

 

Thank you, one and all, for your advice and suggestions.

You'd thnk that at my age this would be old hat. On the contrary, this is the very first time I've been faced with this.

 

Sorry, my wife yelled at me for HAMBing and I thought I finished. Mr. Brillman. He’s the type of guy that rattles off part numbers without looking them up.

 

Thanx.

 

I have OEM , point ignition and R coil on my 32 . I dare say if you click the ignition sw ., there is life in the engine .

Aftermarket coil : Big Yellow Accel .

 

If your changing ignitions, I would always follow their recommendations. If you can find an older Mallory oil filled box style for a point ignition, they were great.

 

I think the ballast resistor was added as an expediency more than anything else. When the OEMs made the switch to 12V, this allowed them to continue using the existing '6V' coils rather than coming up with a new coil that would perform the same or better on straight 12V. The starting bypass was more of a happy coincidence than anything else, although it did improve starting.

Again, the main reasons for the ballast resistor are to reduce point burning and coil overheating. If you could eliminate the points burning with everything else remaining the same, you would then burn up your coil unless you ran the motor at high RPM only.

A coil is nothing more than a small transformer (or to be more technically correct, an autoformer). It contains two coils around a common iron core with the turns ratio between the coils determining the amount of step up or down. There are other design considerations such as interleaving and winding/core shapes but those aren't needed for this discussion. Automotive coils are pretty simple as a general rule.

Where the overheating problem comes in is dwell. Yep, that number you try to hit when setting your points. That number represents the amount of time as measured in camshaft degrees how long the coil is energized. So lets do a bit of math... A V8 motor idling at 600 RPM will fire the spark plugs 300 times per minute. Take 60 seconds and divide by 300 and that gives you .2 second between each spark event. But actual 'on' time is determined by the dwell, typically around 28 degrees. 8 X 28 = 224 degrees out of 720 camshaft degrees. Divide 224 by 720 camshaft degrees and the points are actually closed only 31% of the time between events. Multiply .2 X .31 = .062 second at 600 RPM. As RPM goes up, actual 'on' time goes down. So at 6000 RPM, 'on' time is now down to only .0062 second.

This excessive 'on' time is the problem. When current is applied to the coil, it rushes in and builds the magnetic field that will generate the spark when power is removed and the field collapses. But it only takes a few milliseconds to build that field at which point the coil has reached 'saturation'. Once there, the coil sees the 'extra' power as a dead short and tries to radiate it away as heat. So at lower speeds, the coil 'on' time can be as much as 30 times longer than it needs to be, producing excess heat, but reducing as RPM goes up. If you have a motor capable of much higher RPM than used in these calculations, you may not have enough 'on' time at maximum RPM and would need to increase dwell but that will make the low-speed heating even worse. Because the coil switching is purely mechanical with no way to change dwell time over the RPM range, a ballast resistor is used to limit current down to a tolerable level but with a loss in ignition efficiency. Those large coils that Mallory and Accel used to sell weren't particularly 'special' in their output, the size was to handle/dissipate the heat better. Look at the size of a HEI coil, those are half the size of a 'regular' coil and will fire any 'normal' ignition load.

There's any number of electronic ignition available that address this, with multiple ways to do it.

 

Steve,

My brain is now frying and my eyeballs are spinning. The hardest 5 hours of "B" I ever got at University of Missouri was a circuits class that non electrical engineers had to take. I studied and worked my a$$ off and somehow got a B. I think that 5 minutes after the semester was over I had forgotten 95% of what I was supposed to learn. That was over 50 years ago.

Thanx for the explanation. I think I comprehended most of it.

 

Pertronix recommends using a 0.6 ohm coil with their igniter 3. I bought one of their .6 ohm coils and checked it. it checked out at 2.0 ohms.