What spark plugs are you using in your 915 heads?

[Geoff 2]

The problem with statements like...more hp with later type spark plugs tends to refer/concentrate on peak hp, eg it made 10 hp more at 5800 rpm.
No mention of the smoother idle that occurred when a different spark plug was tried. The smoother idle is a result of more hp at idle rpms because there are less misfires, a rough idle being caused by misfires.


And changing to 'later' spark plugs can certainly add more HP as referenced in post #16 if the ign system itself is marginal. Such as a points ign system. Going to 'later' Platinum or Iridium plugs that require less arc over voltage could certainly improve ign with a marginal ign system, in two ways: less misfires & bigger plug gaps. Think about why dual point dists were used; it wasn't because the factory over-ordered on the pints & had to get rid of them......

 

[Sinitro]

Resistor plugs are strictly for ignition noise on the radio. They were also mandated by the government to prevent noise due to RADIO FREQUENCY interference???? The 2 plugs noted are available on line and work well in my RS23V0A, an origional 6 barrel car with a Prestolite Dual point distributor system. The plugs are NON PROJECED CENTER ELECTRODE CONFIGURATION......
BOB RENTON

To add to Bobs comments..
Early RF radio transmitters were of a spark gap design..
And during the 50s the US government strongly recommended to the major auto brands to go to graphite-based ignition spark-plug wires as to decrease RF interference for AM band radios. I recall back then the AM radio tuning dials actually had little triangle ICONs for CD (Civil Defense) @ 640KZ and 1240KZ. Note that Tesla cars have NO AM band, due to the RF interference coming from their high-powered inverters, RF interference is very common for the later car and entertainment products that utilize digital switching amplifiers and power supplies. AM radios have no noise limiters, but the majority of the later digital switching amplifiers and power supplies operate in the AM band. Even some higher-end car audio components actually change the digital switching frequency of their amplifiers and power supplies to outside the AM band when the user is operating the AM radio.

Just my $0.02...

 

[RJRENTON]

The problem with statements like...more hp with later type spark plugs tends to refer/concentrate on peak hp, eg it made 10 hp more at 5800 rpm.
No mention of the smoother idle that occurred when a different spark plug was tried. The smoother idle is a result of more hp at idle rpms because there are less misfires, a rough idle being caused by misfires.


And changing to 'later' spark plugs can certainly add more HP as referenced in post #16 if the ign system itself is marginal. Such as a points ign system. Going to 'later' Platinum or Iridium plugs that require less arc over voltage could certainly improve ign with a marginal ign system, in two ways: less misfires & bigger plug gaps. Think about why dual point dists were used; it wasn't because the factory over-ordered on the pints & had to get rid of them......5

What a stupid thing to say....."Think about why dual point dists were used; it wasn't because the factory over-ordered on the pints & had to get rid of them......".<
Undocumented hearsay....or....typical sales information presented as an inducement for the uneducated or gullible person to purchase the more expensive plug (regardless of brand) to playcate the individual's desire to claim horsepower increase, smoother idle, better starting, better MPG, etc., and to demonstratue to his/hers cruise buddies how much better the engine runs, using the time-honored "seat of the pants" engineering principles.......
BOB RENTON