AO Platinum Member
Join Date: Feb 2002
Location: The land that Time forgot
Re: spark plugs
Silverstone is an 8-valve, innit?
There's only 2 things to worry about with a spark plug:
a) Will it fit?
b) Is it the correct heat rating?
First is simple.. take a plug out and compare it to the Bosch doodah. Obviously the thread has to be the same width but also check whether the old or new plug has a projecting nose electrode (the centre ceramic sticks out higher than the level of the thread. i.e. Not the metal stub.. the bit it's mounted in.
Obviously this makes the reach of the plug longer. Don't put projecting nose plugs into a non-projecting hole, or it'll head-butt the pistons.
Number and type of outer electrodes doesn't matter.. so long as the overall "height" (all the stuff beneath the bottom of the gasket) of the plug is the same as on the one you're taking out.
Second one is more tricky. Most manufacturers use the number to signify the heat rating. Typically NGK use 6-7-8 etc. Champion use 8-7-6 etc. where the plug is "colder" the further left to right you go.
A "cold" plug dissipates heat better so it runs colder. It's better for high heat engines (turbos and motorbikes etc.) It doesn't matter too much if your plug is too cold but if it doesn't heat up enough (your engine may be too puny for it) then it'll start fouling up.
A "hot" plug is more like it.. but a too hot plug may not be able to cool down enough, so will melt and fall apart. A bit more serious.
I think Bosch "5" is a middle range heat rating, so you should be okay if your engine is standard. All the other letters denote what size thread, internal construction etc. it has. I'm not expert on Bosch.. but if the size fits and the heat rating okay, the other stuff is academic.
3) Oh.. and some plugs are "resistor" plugs.. if your radio reception disappears then you need a resistor plug. It stops the ignition interfering with radio signals etc. if your car has no other suppression devices built in.
I think most plugs now are resistor plugs because of all the on-car electronics these days. It makes no difference if you use a resistor plug in a car that doesn't strictly need it.
No bullets for Chaingun..