Paul Huizenga
Well-Known Member
Going one step colder is a good place to start, and copper plugs are agreeably cheap, so it's not like you're going to break the bank trying to narrow it down. You'll know you've gone too far when you start fouling plugs, but other than that, it's unlikely you'll have any other ill effects.
Autolite (for example - not expressing a preference here) lists their part number 764 for the 1998 Cobra. The other things you need to know are the reach (.708"), hex (5/8"), seat (tapered), and thread diameter (14mm).
A little digging around on the Autolite website also reveals their guide to part numbers:
http://www.autolite.com/pdf/SparkPlugNumberingSystem.pdf
In Autolite's nomenclature, lower numbers for the final digit indicate cooler plugs, so one step colder would, in theory, be part number 763. Unfortunately, 764 is as cold as the Autolite plugs go.
Champion lists part number RS12YC for your car - their numbering range also puts low as cold, so we'd want something like a RS11YC, but unfortunately the closest they offer is a RS9YC, which may be too cold. Once again, though, as long as the other dimensions are the same (especially the reach) you're not going to do anything worse than foul a set of plugs by trying them.
Autolite (for example - not expressing a preference here) lists their part number 764 for the 1998 Cobra. The other things you need to know are the reach (.708"), hex (5/8"), seat (tapered), and thread diameter (14mm).
A little digging around on the Autolite website also reveals their guide to part numbers:
http://www.autolite.com/pdf/SparkPlugNumberingSystem.pdf
In Autolite's nomenclature, lower numbers for the final digit indicate cooler plugs, so one step colder would, in theory, be part number 763. Unfortunately, 764 is as cold as the Autolite plugs go.
Champion lists part number RS12YC for your car - their numbering range also puts low as cold, so we'd want something like a RS11YC, but unfortunately the closest they offer is a RS9YC, which may be too cold. Once again, though, as long as the other dimensions are the same (especially the reach) you're not going to do anything worse than foul a set of plugs by trying them.