Farm Equipment - AC 45B spark plugs

Print Page | Close Window

AC 45B spark plugs

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=23921
Printed Date: 27 Jul 2025 at 11:22am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: AC 45B spark plugs

Posted By: TedBuiskerN.IL.
Subject: AC 45B spark plugs
Date Posted: 11 Jan 2011 at 11:09pm

Can anyone here tell me what a "series gap" spark plug is? Found these old AC 45B plugs at an old parts place, and they cross reference to a Champion J8C, so they should work in the AC tractors that use a 45 plug. These are really old plugs, I'd say from the 50's or earlier. Might be worth looking for at old automotive job shops, but the "series gap" puzzles me.

-------------
Most problems can be solved with the proper application of high explosives.

Replies:

Posted By: JC-WI
Date Posted: 11 Jan 2011 at 11:39pm

Some plug manufactors had a set gap for certain plugs... Yes, one is suppose to check the gaps and set according to engine manufactors specs. AC plugs had lots of definitions but the 45 is the heat range. Check to see if these plugs are 14mm or not.

Did not find anything on a 45B.

45C was a commercial plug..which they had a threaded top to tight the spark plug wires under..used in old tractors, industrial engines etc.,

45 S had a length that wa not threaded at end of plug past the threads,

XL means extended reach,

There are other definitions that were used over the years but lot of those plugs are considered obsolete now so are not supplied by manufactors anymore...specially the ones that one to china to have them made.

Don't know if its true or not but somebody said that AC plugs are now bought from champion that has a facility across the waters. If the base does not have the old AC knurled ring around the base, its foriegn made. (I can't prove that statement but the last AC plugs I bought were smooth and did not say made in USA on them)