[RobMcQuarie]

Mike,
If you are running a girdle, you must use a spacer. The covers actually have a hard time clearing roller rockers with high lift cams. I have a customer's 530 stroker w/roller rockers sitting here in the shop that we used these same covers on - and had to use the spacers. Blue Thunder makes these covers in four versions, from plain finned to "Cobra 429/460/500+" lettering, but they are all the same design.

There are two valve cover spacer designs available though, one is simply a cast alum spacer-same finish as the covers. The second one is identical, except it comes with a rubber o-ring that fits into a groove on the bottom of the spacer. The spacer is then sealed to the head with supplied valve cover studs that hold it to the head. This allows R&R of the covers without disturbing the spacer. You simply run a gasket between the spacer and valve cover as normal. As we quite often need spacers for the Blue Thunder valve covers we sell, we stock the o-ring version of the spacers as they are the best designl. They are a trick piece.

If you don't want to use a spacer, there is a new design, tall, cast aluminum valve cover available that is pretty sharp. It is plain cast, without any logo's though.
Rob