Patrick Dykes of Patrick's truck parts says he has seen many modified 235's on dynos.He told me on the phone, 200 hp is generally beyond streetable on a non supercharged engine. He quotes 160-170 for the 235 and maybe 200 for a 261.Jack Halton says a well prepped 302 GMC might make 250 HP for street use with its much better head design. To get big HP numbers you need to go for RPM levels that get the crankshaft harmonics doing all sorts of bad stuff to long term reliability.Or go for a hyper expensive custom alloy head.You could supercharge(exhaust or belt driven), make a mistake here and its a $$$ meltdown.The poor breathing head is the main limiting factor for power , along with the heavy, somewhat poorly supported crankshaft.Besides we are dealing with 50 year old parts here.Leo Sanducci used to drag race all out heavily modified 261's. He claims around 280-300 HP for a drag engine on gasoline.These are vintage engines, keeping the modification in line with reality gives a smooth running engine with almost stock reliability.
