Champion R-7 Spark Plug alternative?

[Buccaneer]

I’ve been trying to cross reference the old Champion R-7
spark plug with a modern equivalent searching on this
site and elsewhere, but not sure what to believe.
One search suggest using Champion 506, which
shows up as a "resistor" plug, and another suggest
Champion D8 which seems to be an obsolete number.

I’m told the R-7 was considered a "racing" plug.
What makes it so?

Prepare to be boarded!

[garry-in-michigan]

The Champion 506 replaces the R7, NGK AB7 . . . The side electrode in the R7 was thought to give a more open spark for faster ignition – 😀

[Buccaneer]

Garry, Thanks for the reply. EBay is calling
the Champion 506 a "Resistor" plug,
which is taboo for magneto ignition from
what I understand. Correct?

Prepare to be boarded!

[outbdnut2]

Not sure about an R7, but a Champion 7 is now a Champion D16.
Dave

[garry-in-michigan]

Yes – resister plugs are only used only in CD ignition systems – I don’t know how that resistor snuck in their . . . 😎

[Buccaneer]

I seen a YouTube video where a guy removed the resistor inside
a sparkplug, and replaced it with a piece of solid copper wire.
Anyone try that?

Prepare to be boarded!

[david-bartlett]

I would use the NGK AB7. I have used the NGK’s with good results.

[westwind]

Autolite 373 is nonresistor and should match the R7 OK too.

[Buccaneer]

Thanks David and Westwind. Looks like both
plugs are readily available too!
Just bought the NGK AB-7.
They’re exactly in the middle of the NGK heat range,
as is the original specified Champion R-7

The AB-7 specs show it as Non-Resistor, 1/2" reach and
with a removable nut. Perfect!

Shell
Thread Size: 18mm
Thread Pitch: 1.5mm
Seat Type: Gasket
Resistor: No
Reach: 12mm (.472")
Hex Size: 13/16" (21mm)
Terminal Type: Removable Nut
Overall Height: ISO
Gap: .028" (0.7mm)
Center Electrode
Material: Nickel
Type: Standard
Size: 2.5mm
Projection: Non-Projected
Ground Electrode
Material: Nickel
Type: Standard
Quantity: 1
Specifications
Torque Specs: Cast Iron: 25.3-32.5 lb. ft. Aluminum: 25.3-28.9 lb. ft.
Brand: NGK
Heat Range: 7
Longevity: 30k

Prepare to be boarded!

[westwind]

It’s surprising how many of the old plugs are still available. I ordered some for my Row Boat Motor, almost 100 yrs old and plugs are still available.

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