AFR 165s.. sparkplug questions..

[Schlodes]

When I bought my heads, the blue instruction sheets said to use Autolite 3924s for sparkplugs.

If I remember correctly, an Autolite 3924 is one heat range colder than stock plugs.. and they were what I used when I had my nitrous on waaay back when.. with stock heads. So how come AFR reccommends one heat range colder for the AFR heads in a naturally aspirated setup? Shouldn't I be using 3925s? [I think thats the autolite equiv to stock heat range Motorcraft plugs].

I suppose its no big deal because i'm going to install the nitrous next weekend and I guess i'll just stay with the 3924s... But I just wondered why AFR reccommends them instead of stock heat range?

 

[Schlodes]

ttt

 

[04sleeper]

Autolite 24's and 25's were both used in stock factory Mustangs. It just depended on the year. I have found that the 24's run better in N/A. As far as the plugs for your AFR's, you should go with the 3924's. I have run several types of aluminum heads including AFR, Edelbrock, and TFS. The 3924 has run the best out of the plugs I have tried.

The "39" in 3924 means that the pulg has a longer thread for use with aluminum heads. The 24's have a shorter thread length.