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View Full Version : NGK BR6FS "vs" AC MR43T



MOP
06-22-2010, 05:11 PM
Last spring after three faithful seasons on my AC 43T's I decided to try NGK BR6FS supposedly the direct replacement for the AC's. Boat has been running decent but I got a bug to check the NGK's, I put about 35 hours on last year. When I pulled the AC's out last spring I had that why bother feeling, they were spotless with -0- signs of tip wear. Upon pulling the NGK's it was easy they were a colder plug, they were a good color but a bit cruddy. They were not handling the 750 Holley well enough to suit me, they would be fine in a 650 or under engine. Bummer is I was handed a new set of NGK's over the winter so I stuck them in but will put my faithful AC's back in next season. Do no take this as knocking NGK they are a very good plug but BR6FS in not good for a 383 with a 750 Holley.

cvx
06-22-2010, 06:05 PM
I was a little suspect of my NGK's too, ran the same set of AC's for 3 years in a similar engine. Then when I built my 406 sbc w/Dart heads,770 Holley. I installed R5671A-7 NGK's. Now at least 2 plugs foul at the beginning of each season. Think I'm gonna replace the NGK's with an AC equivilant.

tmh
06-22-2010, 08:30 PM
For a 2003 350/300 MPI engine I bought a set of NGK BPR6EFS today as NGK's always run well in my old BMW's. I'll try the AC plugs next time. The shop manual shows 41-932 for the AC plugs that apparently has been superceded to 41-993 in a platinum plug. I've seen posts that recommend the MR43LTS for small blocks. What AC plug should I buy next time?
Thanks.

MOP
06-22-2010, 09:47 PM
There is nothing wrong with NGK's they make a very good plug, I did a little reading their heat range is wider I guess to cover more applications. I will not write them off and may email them for advice. Bonnie says I need to run harder to keep them clean, maybe she is right I tend to sit on about 3400 with only an occasional minute or two blast. Ooops now you know who the hot rod in the family is!!!!!:nilly:

Phil

MOP
06-22-2010, 09:50 PM
For almost all SBC's MR43T seem to be the most revered, I have never ever had a issue with them.

Walt. H.
06-23-2010, 01:49 AM
Last spring after three faithful seasons on my AC 43T's I decided to try NGK BR6FS supposedly the direct replacement for the AC's. Boat has been running decent but I got a bug to check the NGK's, I put about 35 hours on last year. When I pulled the AC's out last spring I had that why bother feeling, they were spotless with -0- signs of tip wear. Upon pulling the NGK's it was easy they were a colder plug, they were a good color but a bit cruddy. They were not handling the 750 Holley well enough to suit me, they would be fine in a 650 or under engine. Bummer is I was handed a new set of NGK's over the winter so I stuck them in but will put my faithful AC's back in next season. Do no take this as knocking NGK they are a very good plug but BR6FS in not good for a 383 with a 750 Holley.

I was a little suspect of my NGK's too, ran the same set of AC's for 3 years in a similar engine. Then when I built my 406 sbc w/Dart heads,770 Holley. I installed R5671A-7 NGK's. Now at least 2 plugs foul at the beginning of each season. Think I'm gonna replace the NGK's with an AC equivilant.
Hey Phil & Jeff,
You know the old saying: If it isn't broken don't fix it!

My small & big block Chev's in both boats luv those AC 43 TR's too! :wink:
This year I only replaced the cap & rotor after doing my ign check inspection.

BUIZILLA
06-23-2010, 07:01 AM
pre vortec and post vortec and aftermarket heads ALL take different plug reaches..

a catalog isn't going to show you what's best

requires visual inspection for chamber orientation

personally, I like Denso's

Walt. H.
06-24-2010, 12:52 AM
Hey Phil & Jeff,
You know the old saying: If it isn't broken don't fix it!

My small & big block Chev's in both boats luv those AC 43 TR's too! :wink:
This year I only replaced the cap & rotor after doing my ign check inspection.
Seeing my error above, I should have written AC MR-43T for both of my engines.

thehow33
06-27-2010, 09:09 AM
There is nothing wrong with NGK's they make a very good plug, I did a little reading their heat range is wider I guess to cover more applications. I will not write them off and may email them for advice. Bonnie says I need to run harder to keep them clean, maybe she is right I tend to sit on about 3400 with only an occasional minute or two blast. Ooops now you know who the hot rod in the family is!!!!!:nilly:
Phil

pre vortec and post vortec and aftermarket heads ALL take different plug reaches..
a catalog isn't going to show you what's best
requires visual inspection for chamber orientation
personally, I like Denso's

My neighbor use to work for Denso and did lots of testing with many plugs. He said the NGK's are better than the AC's because they have a wider heat range like phil said and they last a lot longer. He also said Denso makes most of the plugs out there from some autolite to ac's to motorcraft.