[stomper]

I run lead substitute in my '72 K5. I have always considered it cheap insurance with leaded heads.

I forgot to add the lead substitute on a trip over the pass a couple weeks ago. I heard a definite ping when loading the engine at part throttle. The ping went away on the next tank full with additive driving the same trip. So, I feel it definitely helps my rig and straight unleaded could be the source for problems for you. Give it a try.

Of course, this assumes your engine has original engine with leaded heads, proper tune and you know all about compression, cooling, timing, etc...