Lodge CB14 with right-angled caps. 14mm thread, 3/4" reach, 0.030" gap. Correct torque setting is 18-25.3 lbs ft.
Original leads were black, rubber covered, copper cored.
Occasionally check for wear or other early signs of problems, otherwise none.
Note that many modern spark plugs have gaps set to 0.8mm which is 0.032" (ie. slightly too high). This should not dramatically affect performance.
If fitting new plugs and the engine won't start, it may be due to the plugs having been overtightened - assuming the plugs are indeed sparking.
Examine firing end of spark plugs for common problems :
Pull off HT leads and unscrew plug with a 14mm spark plug wrench.
The following parts are listed as equivalents :-
The Champion plugs are listed as the 'N' having a 14mm thread and 3/4" reach (which is necessary) and the number indicates the heat setting. Apparently the N8 has now been superceded by the N5C.
The official (1950's) Champion cross-reference lists N8B as the equivalent Champion part to the Lodge CL14, CLN, CLN-P, CB14 and CLN-H. The 'B' refers to it having 2 ground electrodes.
NGK plugs are listed as the 'B' having a 14mm thread (which is necessary); an optional 'P' being a projected center; the number indicates the heat setting (smaller is hotter); the 'E' has a 3/4" reach and an optional 'S' being the standard part now. The heat setting suggested by Autolite (4) seems a little high, and the NGK B6ES or NGK BP6ES seem to give good results. The official (2007) NGK cross-reference also lists B6ES as the equivalent NGK part to the Champion N8 and the NGK plugs are often easier to source.
The official (1972) Autolite cross-reference lists the AG5 as being equivalent to the Champion N8 and Lodge CLN-H, but the AG4 as equivalent to the NGK BP6E and Lodge CLN-P. The same source also lists the gap setting as 0.025". The AG5 has previously been tried and is not recommended due to early failures - this source may not be entirely reliable therefore.
Some Rover's apparently used the, now obsolete, Lodge plugs and recommend the Denso W14E as equivalent. The 'W' having a 14mm thread (which is necessary); the number indicates the heat setting (smaller is hotter) and the 'E' has a 3/4" reach.
Note that some manufacturers recommend installing plugs finger tight, then tightening by 1/2 to 3/4 turn.
When trialling the easily obtained NGK B6PES (after previously using NGK B6ES) it was discovered that tightening the plugs as per the manufacturer's recommendations led to the car not starting. The projected tip led to the spark being too far into the chamber - it was necessary to loosen the fit by 1/4 turn to start the car again. This suggests that whenever spark plugs are changed, you should double check the performance of the car and fine tune as necessary. After adjusting the timing, the car started perfectly first time.
To clarify the heat settings of spark plugs, it is only necessary to understand that the spark plug is conducting heat away from the chamber - a 'hotter' plug dissipates heat more slowly and heats up quicker. It is better to err on the side of a slightly 'cooler' plug (which if too 'cool' might lead to carbon deposits not being burnt off and misfiring) rather than the 'hotter' plug (which if too 'hot' might lead to pre-ignition detonation and expensive engine damage).
Note that changing the ignition timing or carrying heavy loads can affect the optimum heat setting.
Weak sparks (or no sparks) are usually due to a defective coil, incorrect plug gap, fouled plugs, or insufficient ignition timing. Many engine problems are wrongly diagnosed as a spark plug misfiring when the real cause is the ignition system or carburettor. Changing the plug may appear to temporarily cure the problem but the problem will soon re-occur.
A 'weak' spark is generally defined as being yellow-ish in color, faint and making a slight noise. A 'strong' spark, in contrast, is usually blue-ish in color, more visible and makes a louder noise.
None yet.