harvester, thank you so so much. that is exactly all what I needed to know. I have the notched aluminum pistons, so that seems to be good. I'm also sure it's the original 1959 engine (235), and I am so sure because I've spoken to all previous owners. as for the reason, my guess right now it's a combination of overheating, a leaking manifold gasket and carbon deposit on the valves.
I'm going to have a little practice run tomorrow on my Buick 248 straight 8, it's quite similar to the 235, and then asap do the big repair on the truck.
thanks!!!
