Replacement of Spark plugs and HT leads.
Whilst the spark plugs and high tension (HT) leads are designed for a reliable 5 year life, some including Roger Parker, advocate the more regular replacement of spark plugs for optimal performance, fuel efficiency and emissions. This is an easy job, so there is no reason why an eager DIYer shouldn't take on a spark plug replacement every 2 years/24000 miles. Here is how it is done.
Spark Plug removal:
Before starting work, make sure that
the engine is cold enough to work on.
HT lead removal:
|Replacement of HT leads follows the
same procedures as the spark plug instructions as above. Here are shown the 8 mm Magnecor
ignition leads as retailed by Brown and Gammons. They are numbered, and are a direct swap
for the original leads.
Mk1 MGF MPi leads run from a distributor mounted to the inlet cam (top right corner of picture, opposite). A further lead runs from the coil tucked under the inlet manifold.
Mk1 VVCs have twin coil ignition, and no distributer - and therefore VVC HT leads are not compatible with leads intended for the MPi.
Later, Mk2/MY2000 MGF and all TFs use MEMS3 engine management. On these engines there are twin coils but mounted in the cylinder head for both MPi and VVC variants. Unsurprisingly the leads are not interchangeable!
Spark Plug FAQs
Frequently Asked Questions: MGF/TF Spark Plugs
A common question come service time is what spark plug to buy when replacement is due. The original fit spark plugs are long-life, 60k mile platinum tipped Champion RC8PYP or Unipart GSP 9652 (MG Rover/ X-Part part number NLP100290 or NLP100290P; Land Rover part number NLP100190) – and these were fitted both to the multi-point injection (MPi) and variable valve control (VVC) engine variants of the 1.8 litre K-series. The smaller-capacity 1.6 also uses the same spark plug.
Do I have to use long-life spark plugs? In fact the answer here is no. Roger Parker has been an exponent of the use of cheaper copper-cored spark plugs – but these will need more regular changes (perhaps every 20k miles). As our MGs get older, the annual mileage tends to drop, so the chances are a 20k mile spark plug will have a very long duration service life. There again, a platinum plug could last decades depending on the use you subject the car to!
Personally, because the cylinder head is made of relatively soft aluminium, I would suggest the use of a long-life plug so as to give the cylinder head an easier time: over-torquing the spark plug can lead to stripping of the thread and an unusable engine. This is not the end of the world fortunately: damaged cylinder heads can usually be recovered using a "Helicoil" – but is a complication best avoided.
Do I have to use the originally specified Champion or Unipart brands? Again the answer is no. Equivalents are widely available from the likes of Bosch and NGK. For example, in the NGK range the single electrode NGK BKR6E, double electrode NGK BKR6EK and platinum tipped NGK PFR6N-11 are all listed as being suitable for the 16-valve K-series engine.
What is the correct electrode gap? For the Rover K-series, this gap should be 0.9 (MGF) or 1.0mm (MGTF), ±0.05mm. I personally would check and confirm the gap out of the box even if they are sold "pre-gapped."
Possible alternative spark plugs for Champion RC8PYP:
Analogous \ Similar Parts of UNIPART GSP9652
ROVER NLP 1001 90 (NLP100190) Analogous / Similar Parts
Description Spark Plug
Spanner Size 16,0 mm
Outer Thread [mm] 14,0
Thread Length [mm] 19
Spark Position [mm] 3,5
Spark Plug 1 - Earthed Electrode
Spark Plug Fixed SAE connector
Spark Plug Nickel Middle Electrode
Spark Plug With gasket seat
Spark Plug interference Suppression 5 kOhm
Assembly Ignition System
Cross numbers KIA 0K55818110
HT lead part numbers: