Petrol engines aircooled spark plugs

kev the rev

Usual recommended plugs

Spark plugs Bosch W8CC

Electrode gap .6mm

Forum Discussion

Gunslinger: Just had this useful info and plugs seem reasonable price too:

Hi Stuart,

The W8CC is the correct plug for your van. The W7CC is a colder plug which you would probably use if you were towing a caravan or something etc

Tom Green The Green Spark Plug Co

=Plugs - heat-range choice

The general rule for plugs is to use the hardest (coldest running) plug, that doesn't oil up or cause poor idling/misfiring - for the conditions of use.

That's the safest.

Idling doesn't matter for a race engine, once started warmed and under way its as cold as allows good pickup from slow sections - this would in the past involve starting on warmer plugs and then changing to a race plug - an extreme example.

For road use, typical load as well as ambient temperatures and engine condition determine what can be tolerated.

Poor cooling, hot intake air or retarded ingition all point to a softer plug overheating, and use of the harder choice

An engine in poor condition, with bad rings, valve seats and low compression can give more oiling, misfiring and idling problems with a harder (colder) plug.

In this case we have two choices which I imagine are quite close together...

In other words a good condition, high compression, clean running engine should easily tolerate the harder choice, and give more confidence in pushing on when everything gets a bit hot. If it's burning a bit of oil and is not spot on, the warmer plug might be the one.

Only you can know, if in fact it matters much, which in general obviously doesn't due to the two recommendations being fairly randomly made...

[HM]