Well in 71 they did change the ratings and methods, but in 71 the emissions started to get more in force, and in 72 there was an even larger drop in HP. You had less compression, a little smaller cam IE less overlap, ignition timing curves were much less agressive. This was done to reduce NOX. You even started to see floor jet EGR to reburn the exhaust gas too. This was a big hit and I think more in Calif the the other states in the early years. Fuel was getting very leaned out too and the introduction to the electronic ignition system was installed too. Smog AIR pumps and a freeway of vacuam lines o control how and when the advance systems and fuel systems managed spark timing etc.
Anyway that was why they felt so much weaker than the warlier cars and could be tuned to run stronger but not as strong.
PS I had my smog License when I was 18 in CA. I did over 10000 smogs in 20 years. I saw all the games that not only the manufactors did but the FEDS and Calif state too. Some cars like Imports had so much lower standards. Part of the reason why US cars were so crappy in the 80s and Toyota and Honda took off. Well this is another story.. sorry!
So I dyno tested many cars and I pulled an old paper chart we made from back in my HS days. In
We had a 70 Satalite rated at 241 that punched out 227 to the crank, and 175 to the rear wheels.
We also had a 72 Duster 318 rated at 150 that punched out 180 to the crank and 125 to the rear wheels.
These numbers keep in mind were on our Clayton Dynos, they like a torque wrench are subject to calibration etc.
With a good tune better fuel jetting and ignition curves we put about 20 HP back into the 72, but it still was much weaker than the older 318. A compression test revealed about 20-30 lbs less per cyl that the older 70 model. I think they went from flat top to a dish piston. :headbang:
Both of these engines and cars had less than 3k miles on them. In fact the Duster had less than 1k, it was a doner from Plymouth to ur school.
