Billet Radiator Cap?

It depends on what you mean.

Does the cap hold no pressure? - Your car could overheat much sooner then designed since without the pressure the boiling point of the coolant is lowered and will allow water vapor pockets to form in the heads.

Does the cap have no means to relieve pressures above 16-18psi? - If your car begins to overheat it will eventually find the weakest link in the system and blow out there once the pressure reaches its breaking point.

Sorry, I guess I worded that wrong.

The cap should hold pressure, don't see any reason it shouldn't besides not having an o-ring or washer.

My concern was that the cap has no way of releasing pressure.

False Alarm!
Dumb A**, me. I didn't even bother to check first if the billet cap fit over the existing cap.

The new billet piece fits over the pressure cap snug. And looks awesome.

Note: If you have thought about purchasing any billet pieces from Robert,

http://www.impalassforum.com/vBulletin/showthread.php?t=231511

Don't hesitate, these are quality pieces, and the prices are great. Not only was shipping quick, but Robert is a great guy to deal with.