Valve guides 1974 911 2.7 MFI
 

I ordered new valve guides from Porsche part no. 93010439100 The guides have an 8mm hole but the valve stems are 8.96 mm Is this normal. Are you required to ream them out?

Do you have an exact measurement? The only air cooled 911's that had 8mm valve guides were 993's.

But yes, guides need to be reamed and honed to size after installation. And if the guide bosses are decent, don't stuff an OS guide in the hole; a standard size will fit just fine. They're purposely made a thou or two over size.

Try https://www.cylinderheadsupply.com/ for reamers and hones.

You have the wrong guides, but the correct ones will need to be honed. There is some distortion to the guide as it is pressed in. Interference of .0005-.001''.

Part number for first oversize is 93010432150. That and the 2nd oversize is all that is offered from Porsche for 2.7L.