[njsteve]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chevy454</div><div class="ubbcode-body">I assume you've checked your timing/dizzy to make sure it's no doing anything wonky like adding too much advance? </div></div>

Yes. It wont even tolerate the factory spec of 8 BTDC. These engines were designed to run on regular unleaded. My prior 1972 455HO in the Trans Am with all the same pieces, except for the unknown mystery cam, would run any gas at all without complant. I had the distrubutor redone and the vac advance limited to 10 degrees and the mechanical set as well, by a very good Pontiac tuner. I have even run it with vac advance blocked. The result was more sluggish but still pinged. The distributor tune improved it dramaticly but it still rattles under full power.