In addition to what Chip said, the 235 types use an exhaust valve identical to the 1.50 valve used on lower performance Chevy small block V-8's, a bigger 1.60 valve is available. The intakes have a longer stem, untique to the 235/261, perhaps a valve from another engine can be machined to match ?Larger valves will certainly help upper rpm power if the engine can use the extra breathing, but will generally reduce low speed power where a street engine operates 95% of the time. Like said above, this is an antique design never intended for high performance work, limited by poor breathing.But it is fun to build them anyway,just keep the limitations in mind and they will blow off Flattie Fomoco V-8's, so all is not doom and gloom.
