Some of what I think is right..based more on experience than books, but with some research done...
67HP 440
- upgraded heads ("915" castings, should have 1.74 ex valves, but many HPs in C bodies had 1.60 ex valves)
-updated camshaft, valve springs, intake, exh manifolding, dist, carb and air cleaner
'68HP 383 335HP
-New for '68 906 casting "440" heads, open chamber, revised intake and exh ports, all 1.74 ex valve from now on
-Revised cam also used in 440HP
-new taller intake, same exh manifolding, 440 sized carb, revised dist, revised air cleaner
'68HP383 330HP
-identical to above, but revised exh manifolding for A body Barracuda and Dart chassis, hence the lower figure.
'68HP440 375HP
-Same "906" heads, cam, etc as above, revised intake and air cleaner
'69HP440 375HP
-Same as '68 models, I think revised intake and carb (mainly due to choke setup...)
-A body design still rated at 375hp, but using special A body manifolds that lost power..not sure how that worked.
'69HP440 390HP 6bbl
-Same "906" heads
-Edelbrock aluminum 3x2bbl intake, same exh manifolding, dual point dist, revised air cleaner assembly
-Revised camshaft and lifters, revised timing set, revised valve springs
'70HP383 335HP
-Same as '68
-revised intake and carb, revised air cleaner assembly
'70HP440 375HP
-Same as '69
-Revised intake and carb, revised air cleaner assembly
'70HP440 390HP 6bbl
-same as '69
-revised connecting rods and balancer
-revised pistons w/valve releifs
-iron 3x2bbl Chrysler intake
'71 is pretty much the same. Interesting notes..HP1 and HP2 are shift indicators of assembly..Not an indicator of 6bbl or 4bbl. The Chrysler engines were rated about 5hp lower. I have no clue why, but I've seen it in articals of the time. The '69 6bbls were supposed to have better rods and pistons, but they couldnt get them out in time. So most '69s have std rods and balancer. "six pac" rods and balancers are std equipment in motorhomes and heavy truck. Not many other 440s came with them in any other year. One "never says never" with Mopar, but I havent seen anything to the contrary in my engines or others'. Iron 6bbls were because then Edelbrock couldnt make enough of them, and they had intake leaks because of the aluminum and iron heads..so those thin paper gaskets were made. Not the thick ones FelPro sells..the real ones are very thin paper. Most "revisions" were to clear specail hoods (cold air) or for emmissions and noise reasons. So revised dont always mean better. To be honest, the machining on the factory stuff was so bad, that most engiens couldnt make the advertised numbers, and those may have been slightly inflated at the time because of how the rating was figured. That's all I know, or accept anyway..Subject to arguemnts and legends...lol
