spark plug spacer?

[djp2k3]

My friend got his engine completely redone by Pro Circuit. They sent him a spacer for the spark plug to raise it higher so the piston won't slam into it due to they cylinder being milled down. One mechanice at PC told him he had to use it, then said he wasn't sure and had the shop manager call him back. He said it was optional. How could that be? Any ideas? Thanks.

 

[marcusgunby]

I think you should keep it-im guessing with the PC mods the bowl of the head is machined alot, and so the plug needs to be raised out the way.

 

[flyinzuki]

Could it be for indexing the plug?
I can't imagine the plug could be that close.

 

[Rich Rohrich]

He said it was optional. How could that be? Any ideas? Thanks.

Clearly it can't be optional.

If they machined the combustion chamber it may need it, but unless you pull the head or come with another way to measure the plug depth with and without the spacer you'll never know for sure.