Help finding missing component values

on the attached pic of an ignition coil driver R and C need to be determined so that the inductive kick will be below the maximum safe voltage of about 400V for a IRF740 MOSFET. The frequency wont be fixed at 300hz as in the example. my question is, what would be some good starting values for R and C. how would i go about calculating these? i know it says to experiment, but im looking for a ball park value to start with. Thanks

i actually have 3 ignition coils here are primary specs if you need it:

1) 6.7mH 1.5Ohm
2)5.9mH .8Ohm
3)6.8mH 1.5Ohm

Are you trying to drive a spark plug? If so, then when the air in the spark gap ionizes the impedance of arc coupled from coil secondary to the primary does a good job of clamping the peak voltage on the primary. Have you ever looked at the voltage across a magneto or point type ignition with a 'scope?

MikeMl said:

Are you trying to drive a spark plug? If so, then when the air in the spark gap ionizes the impedance of arc coupled from coil secondary to the primary does a good job of clamping the peak voltage on the primary. Have you ever looked at the voltage across a magneto or point type ignition with a 'scope?

Click to expand...

This is what im doing:

https://www.youtube.com/watch?v=OMAEF0ScuCs