I have a 72 350 with points distributor , A mild cam , hotter coil.Im running A.C. R45TS plugs gaped at .040.My owner manual said to gap at .040 .I wanted to see what y'all think since it's not exactly stock anymore. Is the R45TS A good heat range for my motor .
.040 is all I would go with points. Look at the spark plugs after they have been in the engine for awhile. If they are light brown to tan, or light gray, the heat range is fine.
I'm wondering in 72 gap is .040,and 71 gap is .030 or .035.They both are pretty much the same motor. I wonder why the difference in the plug gap.
As long as it isn't misfiring, the bigger gap is better. next time you change plugs, try the NGK UR-5. https://www.rockauto.com/en/parts/ngk,2771,spark+plug,7212
