Autolite AF-42s plugs obsolete? - Vintage Mustang Forums

 
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post #1 of 5 (permalink) Old 07-10-2010, 06:05 PM Thread Starter
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Autolite AF-42s plugs obsolete?

Went to pick up plugs for the 351C and asked for the AF-42s, and was told they're obsolete and interchange with the AF-25s. I hate to ASSume with the big box chains, so thought I'd check in here real quick before changing. Thanks.

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post #2 of 5 (permalink) Old 07-10-2010, 07:52 PM
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Autolite site lists various -42 plugs, no AF prefix. Would assume the AF-42's are obsolete. Forget the OEM spec for my 68 390, but a similar story... 40+ year old plugs no longer made.

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post #3 of 5 (permalink) Old 07-10-2010, 08:27 PM
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[QUOTE=dalorzof;3998637]Autolite site lists various -42 plugs, no AF prefix. Would assume the AF-42's are obsolete. Forget the OEM spec for my 68 390, but a similar story... 40+ year old plugs no longer made.

Don't have a solution on the 351C, but for the 390, they were the BF-32 plugs originally.
A VERY close replacement is still available today - Autolite Racing AR33. They are ever
so slightly colder in heat range. If the engine & ignition are in good shape, you won't have
a problem. They are $3-something a plug but if you're running a 390 at this point in time,
the price of spark plugs isn't your greatest concern.....

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post #4 of 5 (permalink) Old 07-10-2010, 08:33 PM
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Quote:
Originally Posted by dalorzof View Post
Autolite site lists various -42 plugs, no AF prefix. Would assume the AF-42's are obsolete. Forget the OEM spec for my 68 390, but a similar story... 40+ year old plugs no longer made.
BF-32. 289HP, 390GT, 428CJ, and others. Autolite dropped them about 30 years ago. Go figure. Very pricey on eBay now.

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post #5 of 5 (permalink) Old 07-10-2010, 09:09 PM
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For your cleveland go ask for Autolite number 25 no letters or prefixes that is the standard plug, If you have high compression and hotter cam and want a colder plug ask for Autolite 24. If you have a MSD or other high energy ignition you can open the gap up to about .40 or .45
Thats what I use and they work, If you want a race plug its Autolite A133

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