Isn't it bad for the heads to run unleaded fuel then?
If you drive sustained rpms (meaing commute on the highway) or run heavy valve springs, yes. If you are building an engine to go to cruise nights, tool around locally, or drag race. You can go a long way before the valves sink. Because your engine is running slightly rich most of the time and the combustion chamber temps are fairly low. It's long, light throttle situations where the seats will erode from the heat and heavy spings. If you have a set of 516s, and they need guides, and 8 seats, plus new intakes and exh, plus springs, retainers, and locks for the valves, you are less than $400 from a set of Edelbrocks that will way out perform them even with the 516s ported. So I consider the work "budget", and I dont qworry so much about having them last for a lifetime. My 516s on my Cuda's 440 have less than 200 miles on them in 8 years. (Maybe I should Ebay my car with the Hemicuda??
) Most seasonal cars around here get maybe 3000 miles a summer. So "cheap" done heads will last for years and years with normal usage. It's all about opinions. I've done both. I'll agree hardened seats are technically "the right way", but truthfully, when the whole picture is taken into account, the "right way" probably doesnt include using 516s.
