Spark plug resistor value

[martinlbb]

Hi everybody,

I'm rebuilding a 712M, and now dealing with distribution.

On this vehicle, it's a military distributor hooked on civilian wires and spark plug connector.

By now, connectors have 10K resistor. Spark plugs have no resistor (NGK BP5ES).

On technical manual, they say a 10K - 15K resistor is okay (wow!).

Have you experienced lowering resistor value for a "standard" 5K?

My idea is removing resistor in wire, and use BPR6ES (internal 5K).

What do you think? Brilliant or dumb?

PS: I've searched on forum before, but without luck

[Stekay]

Wont matter except to your radio's. It's just to damp electromagnetic interference. So yes, go with the resistor plugs.

[martinlbb]

Wont matter except to your radio's. It's just to damp electromagnetic interference. So yes, go with the resistor plugs.

Thanks Stekay for your answer.

And what about spark quality? Having a 15K resistor give worth spark than 5K.

[Jimm391730]

And what about spark quality? Having a 15K resistor give worth spark than 5K.

No real difference, don't worry about it.

Technically, the difference between 5k and 15k resistance in series with the plugs is a few tens of volts (20V? 50V? hard to say exactly) reduction from the 20,000 to 50,000 volts that is needed to spark across the plug. Your spark plug gap defines the voltage that is required -- bigger gap requires a bigger voltage. I won't go into the math of why the voltage drop in the resistor seems so low unless someone really wants to know.

[martinlbb]

OK, you're right. With such high voltage, ohm law won't change much.