Quote:
Originally Posted by "QUICK-SILVER"
Sun tune-up charts, for 69, show the same R44S for engines from 330hp to 370hp for standard/normal(?) driving. Then show R43S for trailer towing and severe service.
So one has to think about what standard/normal driving was in 69 compared to now in order to determine the best heat range for a plug.
Putt-putt around could use an R45S for the plugs heat range/self-cleaning to work.
Where thrashing the hell out of an engine would need something like a R42S.
Clay
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I believe that (speaking purely about 1969 model year 400's) the engines with #48 heads would have have real world compression at or just below 10:1 where as the engines with #62 heads would have have about 9.5-9.0:1 compression.
in essence;
#48 heads = R44S
#62 heads = R45S
The recommendation of going down a heat range for "towing" or driving hard would have meant:
#48 = R43S
#62 = R44S
Now regarding interchange, I personally have never run a champion plug because of all the poor qc issues I have heard or read of - I am sure that at some point before I existed they were a good plug, but that was before my time.
I happened to get a 2002 issue of the autolite spark plug catalog, and used it to do cross referencing for standard plugs (also using google), this is what I get:
(AL = Autolite / CH = Champion / NG = NGK)
R45S = (AL) 85 = (CH) RJ12YC* = (NG) 3332 / XR5
R44S = (AL) 86 = (CH) RJ14YC** = (NG) 5858 / XR4
*From what I am reading, it looks like the champion 11 through 13 heat ranges cross to a Delco 45.
**From what I am reading, it looks like the champion 14 through 20 heat ranges cross to a Delco 44.