.....Hello Everyone, I need to get some plugs at the auto parts store today {that closes in an hour } & the ones I have in the car now are special order racing plugs; Autolite AR3911 Racing Plugs. The store can't cross referrence them & I went to the Auto Lite web site & the plugs that it cross referrences are also special order.... I have a 413 small block Chev., 10 to 1 compression, 232/236 @ .050 cam, 750 double pumper, air gap Performer RPM manafold. The Autolite web site lists these plugs as being for a Big Block Chev.... Can anyone please tell me the heat range that they use if they have a similar motor???? THANKS Bill