Hollow spark plug for 3mm LED

I wanted LEDs to visualize the spark in the printable Toyota Engine and Volvo cylinder head so I scaled the spark plug from mb20music to about 40%, split it in two and made a hole inside it.
I have soldered 3 mm red LEDs to microphone cables inside the spark plugs and glued the tops and bottoms together.
There are of course different ways to go about this if you want spark plugs for your scale engine.
I chose to have the ignition cable "fixed" in the spark plugs and let the solder point be inside the plugs with a shrink tube on one of the LED legs, cutting them at different lengths to stops the ends from being short circuited.
The spark plugs are a little bit too big so you need to expand the holes in the cylinder head or sand them into your required size and shape.
You could of course scale them down further but at least for the printer I am using the walls becomes too thin and the print becomes waste.
I found that for me it worked best to mechanically work on the spark plugs if I printed them in ABS.
Drilling and grinding on either ABS or PLA is best done with care but PLA will be softer and melt at a lower temperature.