LA vs Magnum

needsaresto,
Your right they do crack, the reason being that they are run very lean to manage emissions and the heads are made of harder supposably more durable material. I've only seen a handful that werent cracked.

Mullinax95,
Maybe it was because of the valve size and port volume for the size of the engine that they were going to be used on. I know I'm going to catch some flack here but they are too large for a 273 or 318 engine, and that they wanted to use one setup for both the 318 and the 360 engines. On the 360 engines they work great but the comprimise that they tried to do was use smaller valves so that they would work on both the 318 and the 360 engines. The problem that I see is the port volume is too large along with the valves for the 318. So in this case the 302/318 heads would be the better choice.