91 park ave

I won't buy anything but AC Delco plugs. I can't come up with a real good scientific reason, but it seems that I'll change them once and never have to change them again for as long as I own the car. The cheapy ones (canadian tire, NGK, even champion) I seem to replace after only a year of service.

Steve

Thanks guys, I change my plugs about every other year, Regardless if they need to be or not. I'm over 320k km on this car, so any cheap service I can do to keep it going perfect I just do.

Thanks again, Dan.

The NGKs I bought came pre-gapped and were about $2 each. I didn;t buy the platinum, though. The fact is that you get a more relaible spark with a big conductor surface, though it can wear down faster.(at $2 each, I replace them once a year reguardless of mileage)

There is no such thing as pre-gapped spark plugs, no matter what the zit faced kid behind the counter tells you.

Hi...

Which begs the question if I may?

What would be the noticable/measurable effect of them being incorrectly gapped?

Old retired electrical guy can't help thinking that a spark is a spark is a spark...

Having said that, I bought 'em, installed them, only later to realize that they were gapped to 60 thou and should have been 80.

What effect (if any) can I expect to see when I correct it?

Thanks in advance, and take care.

Ken

Let's list the factors affecting establishing a good spark:

1) The gap size: The bigger the gap, the more juice needed (I seem to remember some old rule of thumb relating that for every thousandth of an inch increase in gap, you needed five thousandth more volts to jump it...I cannot remember exactly). 2) The geometry of the gap: Small pointed electrodes require less voltage. Note that surface conditions makes a big difference. 3) The temperature of the electrodes and the incoming charge: High temperatures allow for low voltage (but increase probability of knock). 4) The density of the charge: High densities (like those under boost) require more voltage to spark. 5) Leakage resistance of the insulator (i.e., electricity always wants to take the easy way out): Maintenance can take care of this. 6) Rate of increase of the voltage at the gap: We are bound by design here, so there is no sense worrying about this. 7) Ionized gases: Their presence, if any, reduces the voltage needed. More of an issue for multi-spark systems than our long duration systems. 8) The air-fuel ratio of the charge: Why? Because it sets the electrical properties of the charge. Lean mixtures are harder on arc initiation than slightly richer ones. 9) Electrode material.

Having obtained a good spark, we still need to obtain ignition. And yes, it has its own list of issues:

1) A combustible mixture must be between the electrodes during arc. 2) Large gaps increase the probability of regular firing - except when #4 above, in which case misfiring can occur. 3) A high density mixture liberates more energy when sparked increasing the probability of flame initiation. 4) It follows that it is easier to ignite slightly rich mixtures than lean ones - so much for gas mileage, eh? 5) The position of a plug and its electrodes in the chamber relative to the flow inside that chamber.

Spark advance. The larger the gap, the later the plugs fire.

The ones I bought were. Unless my gauge and the writing on the package was wrong.(Yes, they checked out as the proper specs the last two times I've bought them)