Charge a cap (electrolytic is o.k.) of about 100uF with rectified mains voltage (300V) through the heater (to limit current) and discharge it in an instant through the SCR and the ignition coils. You don't have to disconnect the mains if you use a one-way rectifier (single diode). Trigger the SCR by hand or with a pulse generator at about one pulse per second max. Don't leave out the gate transformer, as the SCR is on mains voltage. NOTE: Michael Huff adapted this circuit to 120V. He also reports success using a standard SCR.
If you can't find a suitable SCR, you can also use a relay, switch or just two blank cable ends. This actually works alomost as nice as a SCR, but the (relay-, switch-, cable-) contacts will "burn" soon.
These coils give you 8cm or longer sparks of high energy. You can use up to 1000uF caps to increase this. See the "things to do" section for further experiments.
Hints: Usual electrolytic caps are not designed to give high current pulses, they'll get warm. If they get too warm, they might even explode. Your heater will also get hot quickly, especially if your cap is too large or your diode broken. Try to get a (controlled) spark every time you discharge, otherwise you might get one where you donīt want it (in the coils, due to insulation breakdown!).
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