I would still like to know if its a 305 or 307. Excessive RPMs and oldsmobile motors dont mix too well. From the sound of it, your just holding it and wheel-standing. Due to high timing and poor head design, you may want to be carefull under No load. Is it the factory motor? if it is, Be Carefull! you have a set of 5A heads. These can be machined to a tighter squeeze, but they have a sight tendancy to crack under the conditions your describing. So just watch it-allright. From a former 80s cutlass owner to a newbie.

PS: feel free to use that for an avitar