With my spark plugs, how do I determine what gap I should use? Stock gap for my motor is 044 but I have a blower so I usually close it a little. But what if I use racing plugs or just better plugs, can I or should I increase the gap to get a better burn? How would I determine the new gap size?

 

I don't know that "better" plugs would help. Usually newer plugs will have the sharper edges that promote spark jumping. As they get some mileage, those sharp edges wear down, making it more difficult for spark to form.

If you use forced induction and keep the same plug gap, you need to increase the voltage to your spark plug. So something that will help would be an ignition amplifier, like MSD. Then make sure the plug wires are in good shape, or the higher voltage will try to jump through other paths.

 

NGK TR6 gapped at .032. I've used several other brand/types but this one has been the best performer for me.

 

So what about on a N/A motor? I'm running a 42,000V coil and I opened them up to .045, which I think may be too much. Might be better to go down to .040 or so.

 

What I determined is regardless of the plug brand, if it's compatible with your setup, then stick with the stock gap for normally aspirated motors. If you have forced induction, you might want to decrease the gap, depending on the amount of boost. The one exception might be if the plug specifically requires a different gap.

 

But would a bigger spark run better than a small hot one? Or is hotter faster better?

 

If you can run pump fuel you can run stock gap.


Gap has a LOT of factors, too many to get into or for even an answer, but .045 shouldn't be a problem for any decent setup, I run .060 in my truck and have run as much as .100 in a "normal" carb and dizzy engine.