One at a time
.040
.024
A 1968 Ford Galaxie 500 with a 390 engine should use a spark plug such as an E3 brand spark plug. This plug should have a tapered seat with 18mm threads.
1,3,4,2
.040
.028"
.035 is the plug gap.
sparkplug placement for 97 f150 4.6
Johnson 6hp spark plug gap
No...
1-3-4-2
Between 0.025 and 0.028 is recommended.