Correct Spark Plugs for 1969 Z/28

[Edgemontvillage]

There has been much written on the the subject of spark plugs for a 1969 z/28.  The original AC 43R's are too cold and 45S are preferred by some (as are NGK, Autolite 86,Champion RJ14YC, and others) however which version of the R43's are born-with correct, the R43N with ACNITER script and 4 equal width green bands on the ceramic insulator? 

(eBay image) Delco R43N

[Boston14]

I believe those are big block plugs.  The 'N' reach plugs will not seat the gaskets in small block heads.

[Hans L]

Lloyd -

After Jerry MacNeish's finished the engine rebuild for my Z, I asked what the factory installed - he said R43, no suffix (ie - no N or any letters after the 43).

There appear to be several styles available. 
- 1 thin green band on top
- 4 thin green bands
- 1 thick green band on top with three thin green bands

I have not been able to determine which is factory installed.  However, Charley Lillard's 1970 Z28 page, under engine, has a few pics of the original plugs and are the first style, 1 thin green band.   http://www.1970z28camaro.com/engine/    But this is for a 1970 Z28.   So not sure if these were also used in 1969 Z's.

For my Z, I sourced both R44 (Jerry recommends these for driving) and R43's in case I want to be technically correct.

Here's a few pics of the R43's:

[68camaroz28]

Not 100% sure Lloyd but I believe what Hans aforementioned is correct from what I've learned and thought for years, i.e. R43 4 equal bands. I believe the plugs with the 3 equal bands and one thicker band were later plugs and are not considered technically correct. Our 68 has 43 plugs with 4 equal bands.

[Edgemontvillage]

Thanks Hans & Chick.

[68camaroz28]

Thanks Hans & Chick.

Lloyd, I checked my NCRS judging manuals and they do state the plugs should read acniter on porcelain. Note NCRS does not judge for correct spark plugs but do have information concerning correctness in their judging manuals as a "just to know."

[jcabuilder]

Are the R43 ACniter even avilable today?

[firstgenaddict]

Unless you are running nice clean 100+ octane fuel with a hot ignition 43's are way too cold - 44's or 45's are what works in a car with points running 93 octane pump gas.   

[Mike S]

Thanks Hans & Chick.

Lloyd, I checked my NCRS judging manuals and they do state the plugs should read acniter on porcelain. Note NCRS does not judge for correct spark plugs but do have information concerning correctness in their judging manuals as a "just to know."

Chick, was that for 1969 only? I believe R (resistor)plugs began in 1969 to reduce radio interference. 1967 and 1968 did not use R plugs. Acniter appeared on the porcelain in 69 on R plugs if I remember right. Before that the non R plugs were sold as Fire Ring and the porcelain just had A.C. and the number (no Acniter)