Spark Plug 43N please explain this
Thread Starter
Burning Brakes
Joined: Sep 2004
Posts: 945
Likes: 35
From: Lake Dale Indiana
Spark Plug 43N please explain this
Long time ago I picked up a box of 8 ac delco 43N spark plugs for my 65L78. Although I do not run the TI ign (i run points) I was going to change plugs,,rotor etc.
I figured I would just use the 43N's but I never saw a plug like this. It is only threaded half way up ? Please explain
I figured I would just use the 43N's but I never saw a plug like this. It is only threaded half way up ? Please explain
Moderator
Joined: Jun 1999
Posts: 7,117
Likes: 51
From: Dove Mountain Arizona
Long time ago I picked up a box of 8 ac delco 43N spark plugs for my 65L78. Although I do not run the TI ign (i run points) I was going to change plugs,,rotor etc.
I figured I would just use the 43N's but I never saw a plug like this. It is only threaded half way up ? Please explain
I figured I would just use the 43N's but I never saw a plug like this. It is only threaded half way up ? Please explain
Safety Car
Joined: Mar 2009
Posts: 4,191
Likes: 951
From: Corpus Christi, TX
Those half threaded plugs should be ok. There is only about 3/8 inch thread engagement in the plug hole on an old big block head, and there seems to be that much thread. Those plugs seal using the metal ring on the thread base shoulder. 43N is a non-resistor plug, too. They're getting hard to find
Thread Starter
Burning Brakes
Joined: Sep 2004
Posts: 945
Likes: 35
From: Lake Dale Indiana
Well Masterdave If I could go back it time and return them I am going buy up a whole buch of stuff and come back rich. I don't think they sold plugs like these in many many years. I nabbed of ebay bout 4-5 years ago.
I was just courious about the half thread vs. all thead
I actually put the laptop down and went to the books and found pre 1970 heads used the half thread
I was just courious about the half thread vs. all thead
I actually put the laptop down and went to the books and found pre 1970 heads used the half thread
Drifting
Joined: Jul 2005
Posts: 1,977
Likes: 195
From: Putnam Valley, New York. Amateur Radio Operator K2NS
Ac 43n plugs
AC 43N & R43N and the whole series of "N" plugs have always been threaded only half way up the OD. The R43XLS, which is the extended nose version is threaded all the way up. The threads in your heads is at the bottom of the hole and matches up nicely with the 43N or any other 1/2 threaded plug. You can use either 1/2 threaded or full threaded versions with no problem.
RON
Safety Car
Joined: Jan 2006
Posts: 4,786
Likes: 70
From: Park Bench #805 NE Indiana
AC 43N & R43N and the whole series of "N" plugs have always been threaded only half way up the OD. The R43XLS, which is the extended nose version is threaded all the way up. The threads in your heads is at the bottom of the hole and matches up nicely with the 43N or any other 1/2 threaded plug. You can use either 1/2 threaded or full threaded versions with no problem.
RON
there is nothing wrong with placing the AC 43N in your heads... they will be just fine. 
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Intermediate
Joined: Mar 2009
Posts: 27
Likes: 27
From: Wilmington DE
43 N plugs
I ran these in my L72 with early fouling potential---due to the fact they are a cold running plug. R44's are hotter my enging builder told me. Might add I have roller rockers in the solid lifter mill.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Thats a early BB plug that due to its number 3 is a cold plug that is good for racing but not for the street. As noted above the AC replacement is the XLS plugs. I believe older Caddies and I know for sure Chrysler Hemis used them.
Melting Slicks
Joined: Oct 2003
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From: Chapel Hill NC
2025 c3 ('68-'73) of the Year Finalist - Unmodified
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spark plug
I used 43XLS plugs back in the day in my 68 L89 that was my commuter and they fouled within 500 miles.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Long time ago I picked up a box of 8 ac delco 43N spark plugs for my 65L78. Although I do not run the TI ign (i run points) I was going to change plugs,,rotor etc.
I figured I would just use the 43N's but I never saw a plug like this. It is only threaded half way up ? Please explain
I figured I would just use the 43N's but I never saw a plug like this. It is only threaded half way up ? Please explain
Spark plugs don't know what ignition your using and could care less if they could think.....And yes, .035 is the best gap for ALL plugs on all ignitions
You never saw the plug {43N} because its obselete..
