Dual Point vs. HEI

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e50095

e50095

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I bought a sway bar from a guy, and as I was placing it in my trunk he saw the HEI distributor I had picked up at a yard sale. I told him I was considering the HEI upgrade. He went on to tell me that although certainly the HEI is a better set up, he had raced a big block dart for years with a single point distributor. He said his motor didn't rev that high, and although most folks thought he was nuts, the car ran well and never suffered an ignition failure.

I've been watching graveyard carz on the velocity channel a bunch lately, and I can see the value in a stock setup. Besides looking original, it just looks clean. I suppose my question is, given my very mild 318 wont likely see the other side of 4500 rpm's, would I see a gas mileage and power difference at all going with a dual point vs. HEI setup?

I plan to drive my car 150 miles or so one way to the beach a lot next summer, and with 3.21 gears, I'm thinking i'll cruise somewhere in the 26 to 2800 rpm range.

Three months ago I would have thought this was a stupide question and HEI was the way hands down. Now I'm not so sure. Can you shoot me straight?

thanks...

Ken in Pa.
 
Single or dual points? Dual point distributors are MUCH better and MUCH more reliable than (Mopar) single point distributors. They wear out quick, and the way that the advance and bushing wear situation plays out, this causes the vacuum advance to open up the point gap and OVER advance the thing.

If you want "clean" there is/ was someone making a bracket which mounted the HEI under the distributor.

I'm 64, and spent a large part of my life driving "points" equipped vehicles. Some of them were as simple as "once a year" others were a PITA. My first 383 RR had a single point, and I used to carry a bushing kit in the trunk for the thing. I was SO happy to see a cast iron Prestolite dual- point in the 440-6 car!!! But I'm DONE with points if at all possible. I see no reason to go back.
 
Dual points? Or single points? Generally dual point distributors were high performance units.

Really, it all comes down to being a better switch.

The Dwell Angle of a single set of points can only be so large, since they need to open far enough to do the job.

Dual point units use two sets of points with an overlap. That way the time the circuit is closed is longer, allowing the coil to charge for a longer time between firing cycles. This is important at higher RPM's, since it can reach a switching speed of 400 times per second.

Chrysler OEM electronic ignitions are simply a faster switch. They use an electric signal from the distributor to fire the coil with a transistor. Because the transistor can turn on & off faster than the moving point set, the coil charges for a longer time between firing cycles.

So called HEI systems are basically the transistor switch, with a better coil. HEI or E-core type coils can draw more current, and the control circuit is designed to handle that extra current. Instead of turning that electricity in to heat in a ballast resistor, the energy goes in to the coil. Dwell angle or coil charging time is improved, and the higher current in the coil primary translates to more current to the spark plug.

To move beyond a switch & a magnetic coil, you need a power supply. Units like MSD use a power supply to build 300+ volts in a capacitor. They use the coil as a transformer by dumping that capacitor in to the coil very quickly. This is a CD or Capacitor Discharge ignition.

The big question is - How much spark do you need?

That 318 ran ok with a set of points. The OEM electronic unit required less work during a tune-up (no points) but was still limited by the same ballast resistor & used the same coil.

There are many people here reporting improved performance from adding the GM ignition module & coil. Not a surprise, the coil is much better and not wasting power with a ballast resistor.

It is possible to trigger most CD ignitions with a set of points, if you wat to leave the stock distributor in place.

In my experience, it is hard to have "too much" spark. High spark current ignitions seem to provide better starts and better mileage on any car.

Modern systems all went to multiple coils more than a decade ago. On a V8, that means 8 coils, which obviously get to charge 8 times longer. Detroit & Tokyo both keep putting more powerful ignitions on cars, even thought it costs them more money. Must be a reason.

B.
 
HEI is much better. Look at youtube to see videos of sparks jumping a gap, some on FABO too. The dual point was an early stab at the similar idea of a controlled dwell but using a mechanical solution. With HEI, you can open you spark gap to 0.055" for more assured ignition. You might also then lean the mixture for much better mileage.

Show photos of this HEI distributor you bought. Is it a GM distributor w/ coil in cap? If so, not sure that can work in a Mopar, but maybe people have a conversion I don't know of. I have seen aftermarket distributors like that for Mopar, but I read of problems with firewall clearance in A bodies. Most people use just the HEI module with a Mopar e-distributor. The GM 8-pin is nice since they have a cable straight to their external coil. The "ready-to-run" $45 HEI distributor is simplest. Not the exact factory look, but pretty clean and hidden on a small block.

I don't think you will get good mileage with those gears, but you will beat Chevys at stop lights, if that is your thing. Don't need a Hemi.
 
I too have lived with point controlled ignitions eons ago. Now officially an old bastard, I haven’t had a point car for well over thirty years, and haven’t missed their yearly or 12000 mi, or sooner if a PIA car short maintenance cycle.

Yeah, I miss that plugs, points, and condenser jazz about as much as burnt toast and hemorrhoids. LOL

Up grading to stock Mopar electronic distributor, using GM EHI spark control with appropriate coil, less ballast resistor requirement, is a nice upgrade that makes a hotter spark throughout full rpm band.
 
Maybe you would like one of the systems I build.
They are compact, reliable and produce a great HEI spark. (recommend .045 gap)
Comes as a kit with the module, coil and all prewired with three wires to connect.
See here, www.classichei.com
There are members here that have used my ignition system that are very happy with the results. (I use one also) and maybe some will chime in.
Better starting, (cold and hot) smoother idle, more power and better fuel efficiency.
Requires less fuel on the idle circuit also.
They simply work great, and eliminate the coil and wires from the intake as well as ditching the ballast resistor.
The GM 8 pin module is ready for an aftermarket computer controler to plug in via the weatherpack connectors.
This is a picture of mine installed next to my brake booster where the ballast used to be.
 

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bohica2xo said:
Dual points? Or single points? Generally dual point distributors were high performance units.

Really, it all comes down to being a better switch.

The Dwell Angle of a single set of points can only be so large, since they need to open far enough to do the job.

Dual point units use two sets of points with an overlap. That way the time the circuit is closed is longer, allowing the coil to charge for a longer time between firing cycles. This is important at higher RPM's, since it can reach a switching speed of 400 times per second.

Chrysler OEM electronic ignitions are simply a faster switch. They use an electric signal from the distributor to fire the coil with a transistor. Because the transistor can turn on & off faster than the moving point set, the coil charges for a longer time between firing cycles.

So called HEI systems are basically the transistor switch, with a better coil. HEI or E-core type coils can draw more current, and the control circuit is designed to handle that extra current. Instead of turning that electricity in to heat in a ballast resistor, the energy goes in to the coil. Dwell angle or coil charging time is improved, and the higher current in the coil primary translates to more current to the spark plug.

To move beyond a switch & a magnetic coil, you need a power supply. Units like MSD use a power supply to build 300+ volts in a capacitor. They use the coil as a transformer by dumping that capacitor in to the coil very quickly. This is a CD or Capacitor Discharge ignition.

The big question is - How much spark do you need?

That 318 ran ok with a set of points. The OEM electronic unit required less work during a tune-up (no points) but was still limited by the same ballast resistor & used the same coil.

There are many people here reporting improved performance from adding the GM ignition module & coil. Not a surprise, the coil is much better and not wasting power with a ballast resistor.

It is possible to trigger most CD ignitions with a set of points, if you wat to leave the stock distributor in place.

In my experience, it is hard to have "too much" spark. High spark current ignitions seem to provide better starts and better mileage on any car.

Modern systems all went to multiple coils more than a decade ago. On a V8, that means 8 coils, which obviously get to charge 8 times longer. Detroit & Tokyo both keep putting more powerful ignitions on cars, even thought it costs them more money. Must be a reason.

B.
Click to expand...

Nice info thank you - Chris
 
Keep your points on a stock 318. MHO. Simple, rock solid, keep a spare in the glovebox if it makes you feel better. Stock 318 has about 7.5 CR, very easy to light off with a stock coil. New car repairs are all "replace", there is no more fixing. REPLACE does a lot of good in the middle of nowhere if you dont have a REPLACEMENT (except a set of points... :p)
 
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