spark plug analysis

[H48HPE]

Ive changed my spark plugs yesterday, the ones I had in were unipart GSP 2002, these are not shown on the parts CD, but Ive replaced them with a set of Unipart GSP 4462 The prts CD shows these as resistive spark plugs, anyone else experimented with using resistive and non resistive spark plugs? A book I have says they have somthing to do with noise supression.

Also I noticed a strange effect thats occured to the old ones, the colour of the insulator and earth electrode gets lighter from no.1 cylinder down to no.4, any one any ideas what thats all about. photo below:

[MGTurbo]

They look fine to me, fuel distribution is a common problem with a single SU carb and means the outer pistons can run a bit richer/leaner, especially on a 1.3 which has siamesed ports.

Better to use non-resistive plugs for performance, if you dont have any problems with your radio cracking for example then all is ok.

[E_T_V]

Resistive plugs and leads are for electrical noise suppresion. They reduce electrical noise in things like your radio and other electronic equipment like ECU's etc. Nearly all plugs are resistance type now as are HT leads. I can't remember the last time I saw some proper copper leads. The plugs look fine to me too.

[e692wtt]

Plug no 1 has been running the coolest and plug no 4 the hottest, and as a plug runs hotter it burns off any deposits more easily (and so appears lighter in colour as do yours). But why this order? Plug no 1 is at the water pump and thermostat end of the A-series engine, so gets more coolant running past cylinder no 1, whereas coolant is more likely to spend more time around the cylinders progressively further away from the water pump and thermostat, and so this accounts for cylinders nos 2, 3 and 4 running progressively hotter in that order.

Your spark plug condition is fine, don't worry. This effect isn't anything to worry about, either, unless the A-series engine in question is extremely highly tuned.

[Mat_C]

Agree with everything said above but IMHO think you're running a little lean. A series like to run a little rich :)