The Oldsmobile 403 has a fantastic (over square) Bore & stroke ratio for performance... 4.351 bore, 3.385 stroke... but the blocks and cranks were weaker than schit (typical GM stunt)... i've got one in my 79 Trans am, i upgraded to a nodular "N" crank, main studs and straps and a big oil pump... ported W-31 heads, Hi-rise intake, headers & hot cam... makes 425 ft lbs @ the rear wheels... mid range is fantastic, wants to rev like a 302, Wails like a Banshee... but every time the tach gets above 5500 RPM i get a qweezy feeling in my stomach... it's holding up so far... lol
