The basic requirements are a spark that occurs at the right time, and with enough energy to light the fire consistently. Holden six fans are lucky in that there is a ready supply of exceptionally high quality ignitions in the Bosch HEI system as used on countless blue/black engines. Unfortunately there is a fairly common misconception that aftermarket parts are nearly always superior to OEM gear, and I guess this isn't helped by the ad-whores that write for some of the magazines. As far as ignitions go, this couldn't be further from the truth; the OEM Bosch system is superior to aftermarket American systems costing several hundred dollars. Don't be mislead by the aftermarket advertising claims of super high millijoule outputs; these are at best exaggerated and at worst outright lies. I've yet to see any clear performance advantage to multiple sparks either - though I must admit they do seem to improve the idle quality. From a performance point of view a Bosch HEI will be very hard to beat. My other personal favourite is the Delco HEI, and these can be adapted to the little Holden quite easily. More on these later.

The HEI ignitions were originally designed to help meet emission standards on engines with impossibly lean mixtures that were poorly distributed, and diluted with EGR gases. To do this required an ignition that produced radically high spark energy over a wide gap. The Bosch (and the Delco) did the job nicely, and continued to work well even at quite high revs. If you use one of these make sure you also use a compatible coil. In an early model car you may need to fit a relay to make sure the ignition gets a full 12 volt supply. The HEI was originally used with extremely wide gaps, but for high hp use seems to prefer a plug gap of around 40 to 50thou. These dissies have a plastic drive gear as standard, and although they are only lightly loaded they have been known to fail. This is probably more to do with old age rather than any weakness, but whatever the reason, it would probably pay to renew the gear. The earlier metal gear will fit, but stick with a plastic one. It helps to dampen some of the torsional vibrations that make their way to the distributor that would tend to scatter the spark timing. While you're at it, check the shaft and bushes for wear, and also check the advance mechanism. If you've had the module removed for any reason make sure you use a thin layer of thermally conductive grease (try electronics/computer parts suppliers) underneath it to prevent heat related breakdown.

I've always been a fan of Delco dissies (both points and HEI versions). I like the big cap with the widely spaced terminals that helps prevent crossfire, and I especially like the way the advance mechanism is right on top so you can change weights and springs without removing anything more than the cap and rotor. Back when I was playing mainly with Chevs I dabbled with some aftermarket stuff and MSD, Mallory and Accel all got some (a lot, actually) of my money. Once I got the advance curve right with these units they all went exactly as fast as the Delco, so wherever possible that's what I've stuck with ever since. Recently I decided to look into using them on the little six - while the Bosch HEIs are very good, they're getting old and worn and it's a pain in the arse changing the advance curve on them. As it turns out it's almost trivially easy to adapt a Delco HEI from an AMC Jeep 232-258ci six cylinder to the Holden engine. The shaft size is the same, and the diameter of the body where it slips into the block is also the same. The only differences are the gear and a slightly longer distance from the tip of the body to the collar. Here are the conversion details for anyone wanting to make the swap:

  1. Knock the roll pin out and remove the gear. Pull the shaft out from the top (obviously after removing cap and rotor)
  2. Use a small socket or similar to tap the bottom bush up into the body about 3/8"
  3. Trim the bottom of the dissy body to give about 1-1/8" from the bottom of the collar to the bottom of the body (if you hacksaw this make sure you dress the base perfectly square and flat)
  4. Blow any chips out of the body and slip the shaft back in, then refit the thrust washer and the Holden drive gear. Mark the shaft so you can cut off the excess.
  5. Pull the shaft out again and trim it. Use soft jaws to hold it so as not to mark the shaft.
  6. Oil the bushes then refit the shaft, washer and Holden gear. Drill a 3/16" hole through the shaft using the original Holden gear as a guide. Get someone to help you eyeball this to keep it all square if necessary. Obviously you'll want to use a metal gear for this operation even if you'll be using a nylon gear in actual use.
  7. Tap in the roll pin and check that the end float is OK and shim if necessary. Fit the rotor and cap.

  8. That's it, the whole operation probably takes less time than it takes to change springs in a Bosch. You now have a dissy with enough energy to run a six at 8000rpm+ and will be able to make advance curve changes in minutes without even pulling the dissy. Spring and weight kits are readily available for a few dollars. The one in the photo is a repro HEI dissy with adjustable vac. advance and a lifetime warranty that cost me a whopping US$53 + freight, and it takes standard HEI replacement parts. The US racers in classes that must use stock ignitions swear by the Davis DUI dissies that are a bit more expensive at about US$300, however the quality is said to be very good. If you go with one of the cheaper ones take the time to check the rotor to cap phasing. The cheapy in the photo had the rotor nowhere near aligned with the cap posts at the time of firing, however once this was corrected it performed well.

    Jeep HEI distributor
    Delco HEI for a 232-258ci Jeep converted for use with the Holden

    What about points ignitions? They can perform adequately to fairly high rpms and are mandatory in some classes. Their main drawback is the increased maintenance requirement, and for this reason I'd always go for a HEI ignition where these are permitted. The available energy from points ignitions may also be a bit marginal for engines using high boost pressures and/or fuels other than petrol. Dual point Mallory distributors work well and have an adjustable advance mechanism. These units were once quite popular and are still fairly easy to find. If you are limited to a standard distributor the Bosch GB752 points have a higher spring rate and are better suited to high rpm use.

    EFI users have the option of ditching the distributor altogether, thereby doing away with all the timing inaccuracies introduced by the mechanical dissy. Of course there is no reason this hardware can't be used with a carbed engine; it's just that most injection ECUs will have ignition capabilities built in anyway. Builders of higher-revving engines (say 6000rpm and up) should also consider swapping the distributor for a crank triggered ignition. The Bosch unit can easily provide sparks at a sufficiently high rate; the problem is that at higher revs there will always be some amount of torsional vibration of the crank and this will be passed along to the cam and distributor. This vibration can seriously affect the ignitions performance. Ideally the trigger should be located at the flywheel end, where the torsional vibration isn't quite so severe. Trigger points can be attached to the back of the flywheel or flexplate and the inductive sensor mounted under the rear of the crankshaft. There are many advantages to such a system besides reducing the effects of torsional vibration. The timing curve can be set to any shape you want via a laptop, and you can have different maps for different fuels. Rev limiting is built in and adjustable, and the timing can be automatically retarded with boost or with NO2 activation. Ignitech make a range of reasonably priced ignition-only controllers that were originally designed for bike engines but are also ideal for a competition Holden six. See the links section for details.

    Timing is critical, as a starting point you could try about 12deg initial and about 30deg total and tune from there. Don't forget to verify that the marks on the balancer/timing case are accurate before you start. Any street driven engine should be equipped with vacuum advance - it has no effect on drag strip performance but it will definitely help with fuel economy and throttle response when cruising on part throttle. Even competition engines can benefit from vacuum advance - it can help conserve fuel while under the yellow.

    Ignitech Controller
    An Ignitech programmable ignition controller. This drives individual coils and because there is no need for a distributor is ideal for competition engines.

    Crank trigger pickup
    Crank trigger pickup for Ignitech unit above.

    There may be minor power gains to be had from running very high output ignition systems, but if your present system is working well then the improvements are likely to be tiny. Very high energy systems allow the use of quite wide plug gaps that expose more of the mixture to the hotter spark. This results in slightly quicker combustion and a reduction in the amount of ignition advance required. On a horsepower per dollar basis though, the benefits are miniscule. With any high energy system the quality and routing of the high-tension leads is critical.