Does anyone know the inside diameter of the large upper radiator hose neck?

Mine has just cracked on wife's car while she is about 600 miles from home!

I am thinking of trying to insert a piece of copper pipe into it to hold it until she can get home.

Thank you in advance.

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)