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What is the difference between BF42, BF32, AF42 and AF 32? Which is the better plug to use in a 302? I was using BF42 and was told that it was the wrong plug.
 

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BF series plugs are 18mm tapered seat with .468" thread depth
AF series plugs are 14mm tapered seat with .460" thread depth
BF32 plugs are obsolete and were replaced by the current style BF42 plug
 

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BF series plugs are 18mm tapered seat with .468" thread depth
AF series plugs are 14mm tapered seat with .460" thread depth
BF32 plugs are obsolete and were replaced by the current style BF42 plug
That is not 100% correct. BF32's and BF42's are different heat ranges. The BF32's were used in the High Performance Engines. Ford discontinued them but not the BF42's used in passenger cars.

:peeping:
 

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Sorry you are wrong.They were different heat ranges over 20 yrs ago.
20 yrs ago they made a switch to copper cores on spark plugs. The copper core plugs,which by the way the new BF42 is, operate over a broader heat range. this allowed the manufacturers to consolidate the number of plugs they offered. the BF32 was no longer needed as the new copper core plug(BF42)was able to operate over the broader heat range.
 
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