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Why did the Dodge 318 engine lose 80 hp and 60 torque from '71 to '72?

C/PO1 Schneider
04-02-2005, 09:30 AM
I have a 1972 Dodge Coronet Custom with a 318, and was looking for ways to get a little more performance without spending much money. I was under the assumption that my engine made between 210 and 230hp because of various sources that said the 318 made this kind of power. But I just found a specific chart which displays the specifications of Dodge engines from 1966 to 1974, and it says in 1971 the 318 made 230hp and 320 torque while in 1972 it made only 150 hp and 260 torque.

Where did this power go, and how do I get it back? I assume that emissions devices have something to do with it, is there anything I can simply remove to get more power? (such as EGR valve) What parts can I replace to get my 1972 engine to 1971 (or better) specs? I don't want to spend too much money, I can go to about $800.

04-02-2005, 08:30 PM
The big changes back in the 70's was the addition of pollution control. Adding a catalytic converter required the engine to run hotter and to use unleaded gas. Engines back then were not computer driven as today. In order to run the engine hotter, the distributor timing was retarded to top dead center instead of x degrees before tdc and the timing advance mechanism was limited. Running the engine with the timing advanced is great for performance, but the engine runs lean and cool. Emmissions of lean running engines produce pollutants NOX and CO. (I.E. partially burned exhaust gases).
The camshaft was also changed. You will notice all engines in the 70's had drastically lower HP ratings up till about 1980, when the computer started to be used more commonly. The computer allows the timing to be advanced (giving you the power back) and but under control of the oxygen sensors. If a lean burn is detected, the computer retards the timing as needed to run hotter.

04-04-2005, 10:05 AM
The newer motors have lower compression too.

04-07-2005, 03:09 PM
Disabling the EGR valve will likely make the engine ping, especially in warm weather.

04-09-2005, 11:27 AM
During those years, ALL auto makers changed the way they rated horsepower. They used to rate engine HP by putting a basic engine with no accessories on a dyno. They changed to rating it in the car with all accessories on. So the difference is mostly on paper.

08-10-2009, 11:13 PM
Actually you did not lose that much actual POWER. The US Auto Industry changed the way horsepower was listed. They went to NET horsepower in 1972. Many auto mechanics do not even know this, especially younger ones. I know when I drive my my 74 318 Charger I have more than 150 gross HP.

08-23-2009, 02:33 AM
the guys who said the way hp was measured are right, but the guy who said lower compression was also right. the diference was more than just on paper. the way it was measured acounts for about 40 or 50 hp of the 80hp. the compression, heads, intake, etc. acount for the rest. i have never seen a '72 318 with an egr. if it has one it is a newer engine or possibly a california engine, either way it probably has even lower compression. i own a '65 318 & have found it responds very well to increased intake(carb & manifold). you should be able to swing that for less than $800.

01-20-2010, 09:24 AM
they changed the way they mesure hp you may not have the same as most 318s but you r not far off

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