Which Spark Plug???

[Drive35]

Decided to get a new set of plugs and looked on here for best ones. When I took the old ones out though - this is what I found...…


The car has done over 100k miles but seemed to be running OK - shows it doesn't really matter what's in there!!!

[Joes66]

I was watching this interesting u tube video the other day
Seems different plugs do make a change to performance
Just depends if you race an engine or just plod about really I suppose

[malcolm]

Interesting video, until it came to the performance test - why didn't they compare the go kart performance with different plugs?? Test didn't seem to show or prove anything

[christopher storey]

You realise it's bilge when you hear the man refer to "the explosion" . In fact , the flame front in any petrol engine travels amazingly slowly, at a constant speed of about 120 feet per second .This is why variations in ignition timing are necessary as an engine runs faster . The suggestion that a different spark plug provides a different speed of combustion is, putting it politely, misconceived

I would also say that his "running time" tests are laughable, and can be radically skewed by the fact that presumably a partial vacuum is being created in his fuel system , and of course by the fact that even quite small changes in ambient temperature and pressure will create differences of the very small amount noted

[chrisfell]

Two things come to mind.
1. Such a mixture of plugs suggests someone in the past was indifferent to the servicing schedule.
2. That two of the plugs were iridium suggests that the indifference wasn’t necessarily due to cost.

[abowie]

It's hard to fathom whether your eclectic plug mix was a deliberate attempt to correct some problem or just a reflection that in the past our cars weren't worth the price of a set of new plugs.

I would start out, as you probably have, by putting in the correct plugs and then tuning the engine. That should give you an idea of what if anything is going on.

[Drive35]

The car seems to have had a hard life in it's first 20+ years in the USA, but has then been in storage for the other 30. I've yet to find out if the plugs are covering another problem, particularly the iridium ones, so I've left them in the same order!

[Drive35]

Yes - have put a set of Champion N9YC in and it seems to be running fine, but as we can't go too far at the moment, it's not getting a proper test!