Put some spark in your
Quite often it happens that we are requested to fit a Carburetor to an Engine and upon taking the test-drive find a really bad performing motor. Further investigation normally reveals that the customer did his own faultfinding and considered the carb a culprit. If your Vehicle is properly built you will have a decent fuelfilter and therefore a carb will not suddenly go sour on you. Carburetors wear out over a long period and will let you know timeously so you can consult your friendly bankmanger for a Loan (Carbs are expensive).
If you rebuild your Engine, do you rebuild your Carb and Dizzy? Probably not. So if the dizzy shaft falls around in its bore, the timing goes all over the place or not at all, it is time for a rebuild.
Spark is another kitten. Firstly it is important that it occurs at the right time and with the right Quality. I have a business principle wherein I only sell goods that work, and those that I believe you need. If you still run points, do yourself a favor and go for a quality electronic ignition. Either from a later model vehicle or something like the Ignitor. Then fit Quality spark Plug Cables. Cheap carbon types last about a year, OEM about 3 years and Stainless Steel will last many years. The easiest way to check those; is in a pitch dark night with an open Bonnet when the Engine is idling, and see whether you have sparks or haloís anywhere- if yes, replace. If you do not dare to touch your HT Leads with the car running, buy new ones. 5 K ohm resistance, is the Maximum a cable should have (otherwise your Ignition Module might pop).
A coil is just that, normally in an oilbath for cooling. If the end is bulged out, your oilbath overheated (such as when you left the ignition on for too long) and the coil is to be replaced. Of course we also carry RACING coils which are epoxy filled for vibration damping. A 35N$ coil is cheap and you owe it to yourself not to buy it! A coil is saturated by current when your points close, and when they open current is discharged through the HT lead towards your spark plug, this is then supposed to jump the gap which Ignites the mixture in your combustion chamber. If you have a cap and rotor that distributes the spark to the cylinder, they should be replaced once a year or every 50 000 Kís. Consider as your revís increase the coil has less time to saturate and gooi the spark. 8Cyl at 6000 rpm needs the same Energy as a 4 Cyl at 12 000 rpm which is 24 000 sparks a minute! Current always takes the easiest way out and the gap in your spark plug sitting in a high-pressure zone of swirling gas is the most difficult way out. You donít need a million volts of spark (and they will also prefer leaking past the boot onto earth), just enough to ignite the mixture, too much will actually push the fuel molecules out of its way. Remember also that Moisture is an excellent conductor of electricity. Spark current not Voltage ignites Gasoline.
Your fuel ratio, temperature combustion chamber shape and ignition pressure all play an important role in How much energy you need to light the fire. Also remember that a well tuned ignition in good shape gets 6-12% misfires. Furthermore there are 3 accepted theories of how your mixture is actually ignited by the electron transfer across your spark plug electrodes. If you research spark quality you see that it is not only how much you get but also how long it lasts and its profile (rise and decay). The systems that control spark accurately, increase fuel efficiency by 20 %. Spark and Fuel mixture go hand in hand- change one and you HAVE to change the other for optimum results.
Theoretically the most efficient combustion chamber is hemispherical, with the spark plug right in the middle. Ideally we have a squish band going right around the circumference of the piston and head at TDC, which can be a 060gap between the top of the piston and the head, but only at the edge of the piston. This then squirts the mixture towards the center of the combustion chamber where the spark plug sits. On 2 strokes such as the Blaster we can improve the power tremendously by changing the shape of that squish band. If you donít have such a squish band (as on the old Chrysler hemi) you will have to run a low compression (such as 8:1). Simply because the flame front from the spark plug cannot travel smoothly outwards causing air pockets that explode (called detonation). Older BMW boxers sometimes had twin plugs fired in stages, so as to create a second flame front that would incorporate these air pockets giving better combustion and better power. There are also systems that will fire the same plug multiple times ensuring that the mixture is lit, their disadvantage though is that a flame front is always started at the same point. Most combustion chambers are not hemispherical but more bathtub shaped, which compounds the problem of trying to create an equal Combustion within the whole chamber.
See now how important spark is?
Part of the SPARK, is also the sparkplug. Heat range, Nose type, Gap etc. "Race types" belong on the "Race Track". Champion "U" type plugs work great, donít ask me where to get them though. The scope of plugs wiring etc. gets so vast that it could be covered in another Article. The shape of the area where the spark jumps to and from also greatly affects spark Energy and Duration. Remember also to remember small things like making sure you got the best wiring between Coil, Distributor and Power. Putting Coils, Electronic Ignitions, Spark Amplifiers (all Energy Absorbing units) in cool locations is definitely a Good idea.
Maybe you should also look at other Articles I have written such asTune up's, so as to further your Knowledge.
It all ties together somewhere.