MercuryMac
Builder Junky!
Some spark plug threads are unique, [20 threads per inch instead of 18, and an odd diameter]. You may not have a spark plug thread chaser on hand, and if you have aluminium heads, you may run into galling problems removing steel spark plugs. Here's a way to make a thread chaser. Take a good sparkplug and with a zip-cut grinder, cut two curved slots in it crossways to the threads. I cut mine in a slightly counter-clockwise path so the sloughed-off pieces of steel and aluminium will gather and be forced upwards in the slot, not downwards into the cylinder.