AC delco plugs, two differant types work the same

[Bertram38]

Ac Delco 41-933 Platium

AC Delco R 43TS


I have to two L29 454s year 1998 and the other 2000 year made. Both have the same heads and block casting #s and yes they are the peanut heads.

Both head sets have at least 11/16 of threads in the plug hole that matches the AC 41-933 length of threads, I have two of the same motors with differant plugs as listed above. The R 43TS has about 3/8 of threads.

Both motors run awesome and have no differance so far in performance.

I read both sets of plugs to freak out with perfect burn on both engines.

I am confused now, which set should I use for both engines

The 41-933 cost a ton of $, isn't there a standard plug that has a long reach on it but same heat setting as the R-43TS with 11/16 of threads.

Thanks for your time on this.
Kurt

[hoale33]

I would like to know the answer as well. I replaced mine with the longer threaded plugs and saw no difference in performance either.

[glassdave]

a friend of mine that worked in tech at Champion told me that pretty much all of those gimmick plugs (splitfire, Platinum, blah blah blah) dont do anything for performance. Mostly you just need the right plug for your engine and for it to be properly set up.

[jeff1000man]

I looked them up in the Delco book one time and think I have an old set of the number you are looking for tucked away somewhere. I will see if I can run across them next week when I go back over there.

You can go to the auto parts store and tell them you want the Delco book. You can look up the plug and it will give you the stats on the ones you have. Then look up the same characteristice on the line of plugs you want to use.

Sounds complicated, but it isn't once you see what I am talking about.

[PatriYacht]

You should always use a plug that has the right length of threads. Too long and a piston may hit or preignition may occur from glowing of the exposed threads. Too short and deposits will fill the threads and cause problems when you use the correct plug, the exposed threads may glow and cause preignition, performance may suffer from the shielded spark.

[Bertram38]

PatriYacht, yes you are correct, but 1 of my Mercruiser engines came new with the shorty plugs in it, and threads for the long plugs. after removing the AC 41-933 from the other engine is when my ?s arose. I will install the correct plugs in both motors next time around.
I am kinda wondering if the AC 41-933 are the correct plug for marine. Any body have any idea what came in new in all 454 year 1998 too 2000.
Thanks
Kurt

[PatriYacht]

Seems strange but Merc has also sold engines with oval port heads and square port intakes. When the assembly line runs out of one part, maybe they just grab a box of the other instead of shutting it down.

[BradH]

I looked them up in the Delco book one time and think I have an old set of the number you are looking for tucked away somewhere. I will see if I can run across them next week when I go back over there.

You can go to the auto parts store and tell them you want the Delco book. You can look up the plug and it will give you the stats on the ones you have. Then look up the same characteristice on the line of plugs you want to use.

Sounds complicated, but it isn't once you see what I am talking about.

NGK has a great PDF plug guide...know the necessary characteristics (thread, length, heat range, etc) and develop your "own" plug number, which crosses to a stock number. Ex. BKR6EKU which is like a 5446 stock number. Made it really easy choosing heat range, up or down.

Only problem is I can't find it anymore...it's gotta be on their website...somewhere.

Brad.

[Bertram38]

This was the # for NGK plugs BPR6EFS

[OBNOXUS]

Try A/C rapid fires,,,, part #1

[Gordo]

AC/Delco MR 43 CTS Copper tip, (marine)

[Westcoast]

Mr-43lts