Yhat is how they are installed. The counterbore is cut such that the injector face seats below or inside the outer ring... The beveled side of the ring is positioned to seat with the prechamber.

An update on this weekends projects...
I pulled my IP and replaced with a MW style pump from a 1979 300. I did this BTW without removing the oil filter housing...

This did not fix my problem os the slight miss. Seems that it is a "nailing" condition thatnow is causing me to want to shoot it but I willjust keep after these things one at a time.
Next is to check the prechamber seats for wear.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique