Spark plug question

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7

7duster4

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I have a simple question regarding spark plugs. Autolite 66 was listed for my '74 318. But it's not stock, it's mildly built. However the 360 has autolite 65 listed. Is there a real difference in the plugs? Should I have gone with the 65's instead? I did a search and it seems just about everyone running autolites in a small block use the 65 plug. Any info is appreciated.
 
Numbers are the heat range, so there 1 range apart, I think it's smaller #=colder plug , bigger #hotter plug.

4 digit would have the last # to designate the heat range.
 
You are correct. The lower the number, the colder the plug.

IMO, I would not sweat it a bit. After you run the plugs for awhile, you can try a colder one. Normaly, you don't want to go to far in ethier direction. 2 ranges above or below is the most you'll need to try. Stock range is good even for mildly modified cars.

Race cars tend to run a cooler plug.
 
I have always use Champion in my Mopars.This is what mother Mopar used.My buddy talked me into autolites a while back.And after a few hundred miles it became hard to start and ran like ****.I took out the Autolites threw them in the garbage and put in Champions like I should have in the first place.The car was easy to start again and ran great never had another problem.
I had another buddy use Splitfires in his 440.They fouled out after about 25 miles.Splitfire says there plugs dont foul.Ya right I told him to put in Champions and he never had any trouble again.
Jim
 
Thanks everyone

I currently run champs. Never had any problems. I decided to go with autolites just for a change. Many people here seem to really like them, besides they were dirt cheap. Next I plan on getting some taylor 8.2mm wires. Should be a nice set-up.
 
65's are fine in an Autolite without knowing too much of your combo. I have also run the 12y from champion. When I stepped up the carb and headers in the old Swinger stock combo, I went with 63's and/or 9y
 
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