AC Delco spark plug cross reference
Thread Starter
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
AC Delco spark plug cross reference
I have been running a AC Delco plug FR3LS in my AFR heads for years now per recomendation from AFR. These have worked well. I went to the store to get another set and they said no good . They crossed them to an AC Delco 41-629 plug. They look the same but the insulator is smooth where the other plug has ridges. This is the only difference I can see. Length and tip and insulator are all the same length. This is wha ttheir computer crossed over to but the weekend wonder operating the puter I don't know. Iwatched and saw the numbers but can anyone confirm this for sure?
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
For about the last year or more, AC Delco's numbering system has been changed on many plugs. #41-629 is the former FR3LS. I have been using them in my AFR's since the change, and they are identical in heat range. Feel free to use them, they are correct. I got this "straight scoop" from a local reputable auto parts store owner who was notified of the change weeks before he received his first new plugs for sale.
Thread Starter
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Originally Posted by C3 Stroker
For about the last year or more, AC Delco's numbering system has been changed on many plugs. #41-629 is the former FR3LS. I have been using them in my AFR's since the change, and they are identical in heat range. Feel free to use them, they are correct. I got this "straight scoop" from a local reputable auto parts store owner who was notified of the change weeks before he received his first new plugs for sale.
My Chevy jobber tells me the same.
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
thanks for the info.
I clicked on this thread and found the answer to my 86 C4 problem. The plugs that it uses is also 41-629. I replaced them with ACR43TS and the car ran terrible. The parts shop could not give me a cross reference for the AC 41-629 plugs. Now I have the answer from your thread and question. My 86 has aluminum heads, which use the 41-629 plug.
thanks for the info.
kdf
I clicked on this thread and found the answer to my 86 C4 problem. The plugs that it uses is also 41-629. I replaced them with ACR43TS and the car ran terrible. The parts shop could not give me a cross reference for the AC 41-629 plugs. Now I have the answer from your thread and question. My 86 has aluminum heads, which use the 41-629 plug.
thanks for the info.
kdf
