I have approx 13.4:1 Called NGK Tech Line--( great and easy to get real human) they said same plug but -8 We buy them off ebay $19 a set delivered free
Len Hughes said tight gap with Vertex like .018 seems to be working well.
I have been using the newer Kendal GT-1 ( now I think Conoco in TX ) not the same as the old which is now Brad Penn BUT...it is cheap at $38 a case or so and seems to take the alky pretty well
I think Brad Penn is the best but man that stuff is expensive.
I ALWAYS use the brad penn with flat tappets
20w50 may be a little slower than thin oil but with the alky I love it.
On the dyno there IS power in thin oils but I think it just ain't worth it for the kind of running ( mostly show) that we do
Merry Christmas to all
I rebuilt a Powerglide front pump today--just could not stay out of the shop