[Rick_Nelson]

It has always been my understanding that an LS-6 used AC spark plug #R43 and the LS-5 used the R42 plug (if I recall correctly-I'm not at the shop). In my quest to find a set of NOS ones, I spoke to a dealer who said that the LS-6 used the R42TSM and the LS-5 used the R44T. Does anyone know for fact what is correct? I do know they have to be the four green ringed type to be era correct.
Thanks in advance.

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"Details Make the Difference"
Musclecar Restoration and Design

 

[1BadRat]

I am by no means an expert on BBC's, much less on LS-6's, but from my experience the higher the compression, the colder the plug. With the LS-6 having more compression than the LS-5(11.25:1 vs. 10.25:1 -I think?) I would assume the LS-6 would run the R42-43 vs the R44 for the LS-5.

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-Mark TC# 717
ACES #1641
1967 Chevelle SS396/375
1967 RailVelle
1964 Chevelle 283/195
1975 Corvette 396/375

 

[von]

Rick, I have a 1970 Chevy Service Manual purchased in the early '70's. It specifies an AC R43T for 360, 390, and 450 hp 454's.

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von '69 300 Dlx SS TC #15 ACES #1575
My '69 SS

 

[mr70]

R43T-used on LS-6,L-78,LS-5-360HP & 390HP.
R44T-used on L-34 engine.
According to Chevrolet Technical service bulletins and Sun Bulletins.

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Rick Peters
NCOA#1670-ACES#175
1970...ON THE MOVE

 

[Rick_Nelson]

Thanks Gentlemen,

that confirms what I thought I already knew. Now..............if I could just find them. Jefferson turned into a goldmine last weekend but no R43T's!

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"Details Make the Difference"
Musclecar Restoration and Design

 

[LS6-M22]

According to my AMA book the LS6/L78 use R43T.This is the most comprehensive source of information on the LS6/L78 Chevelles.

 

[mr70]

Rick
I have a set of 8 R43t's in the box.I don't want to sell them but you can use for reference if you need to.There was a guy named Don Cressman in Canada who was advertising a set in Clessifieds last year.

 

[Rick_Nelson]

Thanks Rick, send me those plugs and I will use them as a reference for a year or two.

I thought I was correct on the plugs but I just cannot find them. At Jefferson I found a ton of NOS plugs but NO R43T's!! I would even use a set of good used ones but I will stop here as this is turning into a want ad.

Thanks for help all.

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"Details Make the Difference"
Musclecar Restoration and Design