Catalogue reference. Availability, exact specification and OEM or aftermarket supply are confirmed in your quotation.
RN5C Spark Plug
Engine partsPart number: 123
Federal-Mogul 123 is an RN5C resistor spark plug with a copper-core centre electrode, 14 mm thread, 3/4 in reach and flat seat. Check the engine model and serial number to confirm suitability.
Looking for Federal-Mogul 123? This catalogue reference is listed under Engine parts. Send the part number and your equipment details so we can confirm the specification, availability and a quotation including shipping.
Availability on request
Technical specifications
| Manufacturer | Federal-Mogul |
|---|---|
| Part number | 123 |
| Category | Engine parts |
| Availability | On request |
| Reference basis | Manufacturer part-number reference; supply origin requires quotation confirmation |
| Plug type | RN5C |
| Thread diameter | 14 mm |
| Thread reach | 3/4 in (19.05 mm) |
| Hex size | 13/16 in |
| Seat type | Flat, gasket seat |
| Resistor | Yes |
| Terminal | Removable nut |
| Centre electrode core | Copper |
| Ground electrodes | 1 |
Catalogue information may contain errors or be out of date. Full specifications and verified details are available on request. Confirm the part number and equipment fitment with us before ordering.
Product questions
What are the thread size, reach and socket size of the 123 RN5C spark plug?
The RN5C has a 14 mm thread diameter, 3/4 in (19.05 mm) reach and 13/16 in hex. It uses a flat gasket seat. Verify the engine specification before ordering.
Is the 123 RN5C a resistor spark plug, and what terminal does it use?
Yes. The RN5C is a resistor-type plug with a removable terminal nut. Confirm that its resistor design and terminal suit your ignition system.
What spark plug gap should I use for RN5C?
Some listings give a 0.025 in (0.64 mm) pre-gap, while another gives 0.7 mm. The required operating gap depends on the engine; check its specification rather than assuming the listed pre-gap is correct.
Can RN5C replace a different spark plug in my engine?
Do not assume a match from thread size alone: heat range, reach, seat and resistor requirements also matter. Provide the equipment model, engine model and serial number, and the existing plug number for verification.
Researched on:
Research information may be outdated. Confirm fitment and specifications with our team before ordering.