DIameter of Spark Plug Socket Hole in Head
 

Anybody have a head kicking around and a good mic?
I have a 2.4 L motor. I am looking for the diameter of the hole in the head that receives the spark plug socket. Another way to describe this would be " What would be the largest diameter washer that could fit under the sparkplug. I imagine this dimension is the same for 2.0L to 3.2L motors since they all recieve the same size spark plug sockets. I would like to two decimal places if possible.

Thanks,
Adam

At the top its 31.5mm but it is slightly rounded at the bottom where the plug seats.

Thanks Craig.