Resistor vs non resistor spark plug performance

[Randy S.]

Gents,

Just wondering if non resistor plugs will perform better then resistor type. Wouldn't the lack of a resistor in the plug design allow more energy in the spark?

If you need specifics, AC 45S vs AC R45S in a stock 300HP 66.

Randy

[Michael W.]

Re: Resistor vs non resistor spark plug performance

The resistor type plugs may fire an immeasurably small amount of time later than non-resistor, but other than that there's no difference.

The type of spark plug does not vary the amount of energy released in any case, this is a common misconception promoted by the marketeers. $2 AC Delcos give the same results as $20 wizzbangs.

[Duke W.]

Re: Resistor vs non resistor spark plug performance

Gents,

Wouldn't the lack of a resistor in the plug design allow more energy in the spark?

Randy

Yes, but from a practical standpoint, it may not make much difference, especially if the engine is not prone to plug fouling from excessive oil consumption. I don't think GM changed anything else in the ignition system when they went to resistor plugs in 1969, but I'm not sure.

I prefer non resistor plugs, and if you aren't having the car judged, consider the NGK B4 or Denso W14-U, which are equivalent to the AC 45.

Duke

[Bill M.]

Re: Resistor vs non resistor spark plug performance

Back in the day, if you fouled a plug, sometimes you could get it to fire if you pulled the spark plug wire out of the distributor cap and forced the spark to jump a gap. That would help the plug fire, and the combustion heat would sometimes clean the plug enough to get it back in normal operation.

I'm remembering that the resistor plugs were intended to help eliminate mis-fires...even one mis-fire. The resistor did the same thing as pulling the wire out of the cap. I've forgotten the numbers, but one mis-fire spewed a load of unburned hydrocarbons out the tailpipe...no catalytic converters back in those days.

[Duke W.]

Re: Resistor vs non resistor spark plug performance

It's always been my understanding that resistor plugs were introduced to meet stricter RFI emission requirments.

Duke