Bought my replacement engine on Saturday from MX-5 Plus, but instead of picking up a regular 1.6L B6 engine from a NA6 I purchased a 1.6L long engine from the NB6. In Japan, the NB series Roadster (MX-5) had the 1.6L engine up until 2005. The cast iron block is identical, but the head and intake are different. The hydraulic lash adjusters are replaced with solid lifters and cams have more lift. The CAS is no longer used and replaced with a cam position sensor and crank angle sensor. The NB6 also uses the crank-shaft nose/pulley/cog, water pump and oil pump from the 1.8L BP engine.
To run the NB6 engine in a NA6, there are two options. First option is to swap the entire NB6 wiring and ECU into the NA6, the other option is to use the following NA6 items on your NB6 head/block.
- rear water outlet
- front water outlet
- alternator (using the NB6 pulley)
- air con (if you have it)
- power steering (if you have it)
In addition to this, you will need a modified intake cam-shaft. The NB6 intake cam-shaft doesn't have a slot for the CAS, so the NA6 cam-shaft end is cut off and pressed into the NB6 cam-shaft. Pretty straight forward and costs $100 to do.
Now all that info is out of the way, here are some photos of my progress so far.