I have noticed two things about the pop-off valve in my 82SC. The top of the air box is smooth and does not have any ribs like others I have seen and the valve itself must be an older model. It's aluminum and held together with 3 hex head bolts. Instead of a cantilivered design like a toilet tank its a straight action plunger.

Just wondering if anyone can date this arrangement for me and if their are any know problems with this style pop-off. Thanks.