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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » Spark Plug options

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    6/17/2024 6:40 AM  #1

    6t5klassic
    FYI FORD Member

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    Registered: 8/04/2022
    Posts: 23

    Spark Plug options

    Hello all,

    65 fastback, 302, cam and intake (nothing aggressive). Just dialed in my timing (seems to run best at 6-8 degrees BTDC). Love those TDC tools to help find correct marks on balancer! In any case, i am about to swap plugs now that the carb is tuned. I have autolite 25 (14mm threads) in there now, but want to swap for motorcraft. Can anyone confirm if I should be looking at BSF or SP versions of Motorcraft? Not sure i am seeing a good cross-reference to go by here. So, it could be BSF42 maybe or SP420X (or SP450X). Any insight on that or if there is an article here already published, maybe point me to it? 

    thanks much!
     

    Last edited by 6t5klassic (6/17/2024 6:47 AM)

     

    6/17/2024 3:34 PM  #2

    TKOPerformance
    Hyper FYIFORD ADDICT

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    From: Newark, DE
    Registered: 12/15/2014
    Posts: 7,449

    Re: Spark Plug options

    Stock heads I assume?  Why do you want to go away from the Autolites?  IME regular old copper core Autolites provide great spark.  Better than exotic electrode plugs in naturally aspirated engines.  They just don't last as long as a platinum, etc.  But they are cheaper and work better IMO. 

     

    6/17/2024 4:27 PM  #3

    Ron68
    Senior 24-7 FYI Addict

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    From: Mukilteo, Washington
    Registered: 4/01/2013
    Posts: 1,549

    Re: Spark Plug options

    I just posted that I have a set of 8 Motorcraft SP-450A copper spark plugs on the Swap Meet page. Would they work for you?

    68 coupe - 351W, 4R70W, 9" 3.25 -- 65 convertible - 289 4v, C4, 8" 3.00
     

    6/17/2024 8:28 PM  #4

    6t5klassic
    FYI FORD Member

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    Registered: 8/04/2022
    Posts: 23

    Re: Spark Plug options

    Thanks Ron68 - I did already order the SP450X (ASF42CX). Oh wow i did not consider the swap meet page. That is something i didn't know about.

    TKOPerformance - I am not necessarily moving away from Autolite but the plugs need replacing as part of my tune-up and I was just considering Motorcrafts for this round. I do like the Autolite 25 as well.

    thanks much!
     

       •Thread Starter
     

    6/18/2024 1:40 PM  #5

    lowercasesteve
    Senior 24-7 FYI Addict

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    From: Auburn, Ca
    Registered: 4/01/2013
    Posts: 1,253

    Re: Spark Plug options

    Back in 289 days I used BF32's or BF42's successfully, but I can't remember the maker with my aging brain.

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    6/18/2024 2:02 PM  #6

    BobE
    Senior 24-7 FYI Addict

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    From: White Plains, NY
    Registered: 4/04/2013
    Posts: 2,598

    Re: Spark Plug options

    lowercasesteve wrote:

    Back in 289 days I used BF32's or BF42's successfully, but I can't remember the maker with my aging brain.

    Those were Autolites, Ford's brand back in the day. 
    The BF-42's were used in the 289s; the BF-32s were used in the Hi-Po 289s (that had a higher compression ratio) 
     

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

     

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