Numbers on intake and exhaust ports(MC-1)

[Mark Rutherford]

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I just removed the head off the MC in my turbo Coupe GT, after a very bad w=
eekend.  I noticed in the intake and exhaust ports that there were numbers =
stamped in them.  They were values in the 13 to 20 range.  What are they?

Thanks
Mark Rutherford
5kcstq at sisna.com

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