I just removed the plugs (motorcraft awsf 32p) and was in the process of replacing them with autolite ap104 plugs. I noticed the motorcraft plugs have threads half way up (like 3/8" worth of threads) and the autolites have threads all the way up to where the plug seats (a little over 5/8" worth of threads). Is this a problem? I checked with three auto supply places and they all said the ap104 is the right plug. My worry is the plug threads down into the cylinder farther and hits the top of the pistion? Any advice? Thanks, Ron

 

Your not looking at threads. if you look above the thread, u'll see where the plug seats in the hole. thats what u're looking at. also, go with motorcraft, not autolite.

 

The longer thread design was a change done to both motorcraft and autolite plugs - you have the right one. I included a post I made quite a while back about the same subject below. (note its been about 2 years and 40K since I put the autolites in and they have been excellent - no difference I can tell between them and the motorcraft) The key thing is stay away from the gimmick spark plugs with several electrodes - the spark can only jump one gap at a time and the best spark contact is what counts.

Motorcraft has changed a lot of their plug numbers over the past year which makes it a bit of a headache, they added the longer threads recently (maybe because they had so many problems with plugs blowing out of the modular engines? But when I changed my plugs the last time the only thing motorcraft had availible for the 4.6L was a single platinum (at the time) since they changed them all - even though originally ford specified double platinums for replacements. I checked all over for the motorcraft double platinums too. It is true that Autolite makes motorcraft plugs (though some debate about specifications and quality between the two) and some people would only consider motorcraft - as for me I went with the autolite double platiums, had the extra threads too, and they work great. Just my expirience.

 

It doesn't matter if there's too many threads on the plug. Unless you are turning it hard enough that you are making new threads into the head of your engine (which is gonna be impossible unless you heat the engine and have some uber hard metal) , its still only going to thread as far as the factory threads will let it go.