From what I understand, the Motorcraft is one of the few non-resistor plugs we can still buy in the US. But then, you may not be able to buy them at all in Ireland? The Autolite 45s are definintely resistor plugs.
Autolite has not been a part of Ford since 1973. Bobby Kennedy was on an anti-trust crusade back then (politicking for president?) and made Ford quit making their own spark plugs, etc. It was OK for GM to own Delco, but not Ford to own Autolite??? Ford had to sell Autolite to Bendix, i.e. Fram. That was when Motorcraft came into being. This tells me that likely the Fords were Republicans.
Originally Posted by digazz
Thanks for the quick response. I found out on a different forum since that i could use APR6fs insted of the APR5fs. Does this sound right. Also will the pl;ug gap need to be adjusted.
The 'R' is simply a resistor version which makes less RF noise for newer cars with computers. For older cars without electronics the resistor isn't needed but I don't find they hurt anything.
The '6' will be a slightly colder plug than the '5'. Whether a 5 or a 6 is best for you probably depends upon how you drive, etc., and may be a question only you can answer. The gap should be set to the original spec if you still use the original points/condenser. With a higher energy replacement ignition you can open the gap if you like.