Will standard plugs give you the correct heat range in a Prus head? Or is it best to go with 14mm plugs?PK
I'm running original Varcon Gambles department store plugs in mine. By the look of the color (dark tan) they are running perfectly. As far as other brands go, I can't say. But I suspect they will run fine depending on your fuel adjustment.
My Op is go with the 1/2 openings. You can use the adapters if you want to use 14mm plugs but might find that it is hard to find non resister plugs. If you are running coils the resister plugs don't like the voltage spikes I have found that they don't hold up very well. If you use the 1/2 in original type plugs you might find the car runs better. Others will have different OP but that's mine.
I ran old Champion Xs in a Z head, no problems.