What changed was the way they rated the motor, not so much the motor. What makes the difference is the compression ratio. These motors have a ton of torque at low RPM. It been over 15 years but if I remember right a motor I have had 440 ft lbs of torque at 2100 RPM.... I thought it was the 1970 472 rated at 375 hp because it had 10 to 1 compression.

 

As stated above, it's gross horsepower for the 1971 and net horsepower for the '73.

The '73 actually makes more power than the '71 and has better drive ability. The downside is it really does not work properly on 87 octane fuel. 1971 was the first year for lowered compression across General Motors and the Cadillac's performance suffered.

1972 saw the cam timing advanced and performance increased right through the end of the 500 in all RWD era.

I can't prove any of this.

 

As stated above, it's gross horsepower for the 1971 and net horsepower for the '73. The '73 actually makes more power than the '71 and has better drive ability. The downside is it really does not work properly on 87 octane fuel. 1971 was the first year for lowered compression across General Motors and the Cadillac's performance suffered. 1972 saw the cam timing advanced and performance increased right through the end of the 500 in all RWD era. I can't prove any of this.

It actually didn’t have more power. The change you’re asking about is the fact the engine went from 10:1 compression down to 8-8.5:1 and also they added a smog pump. They made the change due to smog as well as to run better on unleaded fuel.

 

The 1971 was already 8.5:1 compression. SAE Gross HP was stated at 345 (365 for the Eldo) with SAE NET HP stated at 220 HP (235 for Eldo). Brochure with info is on the Old Car Brochures site: Directory Index: Cadillac/1971_Cadillac/1971_Cadillac_Brochure_1

A lot was going on in a few short years with insurance and safety concern lowering stated HP on some cars, the change from gross to net HP ratings, and the rapid changes happening with concerns for emissions and fuel economy.

Rodger

 

'71 was a dog. They dished the pistons to lower compression but left cam timing alone.

They fixed it by the time they built my '72 CDV which I traded for a Chry 318 engine in 1979. The CDV had recently suffered some damage in a high speed chase.

I carefully went over everything I could to figure out why the '71 motor didn't stack up to others after replacing the 472 with a 1975 500.

I also prefer the flat top pistons and open chamber heads to dished pistons and closed chamber heads after MANY comparisons.