66-73 stock small block heads?????

ahhhhh....the Age Old Question.


It is BASIC and SIMPLE if you think about it.

273-2bbl, and 318-2bbl.....have the smallest valves 1.78/1.50, lightest duty springs (.450"), smallest ports.

68-70 (X,O,U castings) 340's have 2.02/1.60 valves.... .500" springs, no rotators, and monster ports.

71-73 ( J castings ) 340 heads have 1.88/1.60 valves, .500" springs, no rotators, and very good ports.

587' castings that came on 360's after 1973, and 318-4bbls.....have 1.88/1.60 valves....and not all of them had .500" springs, and some had valve rotators....and eventually got SMOG Air Injection ports phased into production.

302' casting 318 heads......1.78/1.50 valves, weak springs, small ports, small combustion chambers, air injection ports

308' casting 360 heads.....1.88/1.60 valves, .450" springs, enlarged pushrod holes, 340-360 sized ports, air injection ports


^ right there.....