Spark Plugs

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Spark Plugs

Post by keithg on Thu Apr 28, 2016 9:57 pm

The original specified plugs from AC Delco are discontinued. The ones in mine are 44FFS. I just recently discovered this problem. The cross references list the 44fs which is what I ordered from RockAuto. These are shorter and I wonder if the electrode will even reach the combustion chamber. I have found some 45FFS on ebay which should be the correct length. What do you all run? I looked at the NGK BP6HS which should be close but it is still 1mm shorter than the 44FFS for the electrode into the combustion chamber and is not threaded as long.

Pic

Please discuss.

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Re: Spark Plugs

Post by Bill on Thu Apr 28, 2016 10:13 pm

How long have they been discontinued? I put new plugs in last year or the year before. It has been running fine. I can take a look this weekend and see what they are. I didn't even pay attention to what plugs I got - just whatever napa or autozone said would fit.
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Re: Spark Plugs

Post by keithg on Fri Apr 29, 2016 8:05 pm

They have been discontinued for a long time AFAIK. The Aluminum head benefits from having the plug threads being as long as the threaded hole is deep. The AC spark plug decode info is not definitive as to what it a 44FFS really is. It is supposed to be:
4 - 14mm
4 - heat range 4 (0-9)
FF - 12.7mm reach fully threaded
S - Extended tip
(it also lists for S:
S - 22.3mm Moderate Long reach 18.25mm)

As I measured it


  • 44FFS is 12.7 threaded plus another 2.5mm of body smaller than the minor diameter. The electrode is ~17mm from the mount face.
  • The 44FS is 10.5 threaded plus another 1.75mm. The electrode is 14.5mm from the mount face (way short IMO).
  • The BP5HS is 11.5 threaded plus another 1.75mm. The electrode is 16mm form the mount face (Closer).


I do not know how a 5 in NGK compares to a 4 in AC Delco. I use 7's in my turbos and 6's in NA. The NGK looks like it puts the electrode closer to the OEM design. I did not look at Champion or Bosch. Bosch looks expensive. I'll return these 44fs as the electrode will be too far up in the plug hole and get a set of BP6HS

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Re: Spark Plugs

Post by Bill on Sun May 01, 2016 3:05 am

I pulled a plug wire just a bit ago. If I read it right I have champion L87YC plugs. Hope that helps.
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Re: Spark Plugs

Post by keithg on Sun May 01, 2016 8:15 am

Without measuring it, I don't know for sure. I am guessing it is very similar to the 44FS in threaded length and electrode projection. I would like to see a champion X89LY or X89E. This is the champion decoder
http://forums.iboats.com/forum/engine-repair-and-maintenance/johnson-evinrude-outboards/110077-champion-spark-plug-number-decoding

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Re: Spark Plugs

Post by keithg on Wed Jun 01, 2016 9:58 am

The BP6HS plugs ran for 2 weeks and I had no issues. I found my dad had put back 2 complete sets of 44FFS plugs (NOS) and I found them in a box of 'spares' and put them in. I figure, whicl I have a 'correct' set, Might as well use them. Dad's comment was that if you use plugs with the proper length of thread on them after you have run some shorter plugs, you could bind or possibly push carbon into the cylinder.

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Re: Spark Plugs

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