Sounds like you are using stock 7° valve locks, and the retainers are 10° type. 10° locks are roughly 1/16" bigger and have a slightly flatter angle, makes them wider at the top. 10° is pretty much the industry race standard now days.
There are also what is called Super 7 locks, these are larger at the upper end like the 10° locks are but are still the 7° angle, makes then bigger around at the lower end than stock 7°.
Do you have a part # for the retainer you have, or measurements of what you have??