they will throw your coil out-of-tune and then burn up almost instantly. mylar caps have a very high loss at TC frequencies (loss=heat) and in a small coil the loss would be greater than in a larger coil(the higher the freq. the more loss) and even if you found a cap/coil combo that did not burn the caps up,the caps would still get hot and that reduces the spark output(conservation of energy) regards, kevin dalpe