Blueheeler Posted April 11, 2022 Share Posted April 11, 2022 I currently own a 1970 Monte Carlo 350ci 4bb. I believe it was factory rated 300hp. I previously owned a 1974 Monte Carlo 350ci. 4bb. factory rated 160hp. I understand the 74 ratings were with smog pump & other pollution items. Those were all removed. So the best I can tell both engines externally were the same. Both engines have same spark plugs, same gap, both have HEI distributors, both set 10 degrees BTDC timing. Here's what I don't understand, It seems to me that the 74 rated 140hp less had better take off power, more torque and would have probably been quicker in a 1/4 mile than the 70. Did all the pollution crap on the 74 reduce the horsepower 140hp. Are both engines internally the same? Am I expecting to much from my 70? Quote Link to comment Share on other sites More sharing options...
Canuck Posted April 11, 2022 Share Posted April 11, 2022 The HP ratings changed. In 70 they were gross horsepower. Starting in 72 they were rated at net horsepower. The 1974 rating of 160hp can’t be compared to the 300hp of 1970. The 1970 300hp engine had higher compression, more horsepower and more torque than the 74 engine. There’s no doubt about that. I owned a stock 350 4-barrel 1972 Monte and it was not as quick as my stock 350 4-barrel 70 Monte. Both were under 100,000 miles. By 1972 they were using lower compression heads and they made less horsepower by then. 1 Quote Link to comment Share on other sites More sharing options...
Canuck Posted April 11, 2022 Share Posted April 11, 2022 In the 1971 Monte Carlo brochure they listed both the gross and net ratings. You can see the lower compression heads in 1971 already reduced the gross hp from 1970. 1 Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted April 11, 2022 Share Posted April 11, 2022 I belive 74 was the first year for HEI and I think they lowered the compression also, not sure what year they did that may be 73. Quote Link to comment Share on other sites More sharing options...
Blueheeler Posted April 11, 2022 Author Share Posted April 11, 2022 Canuck that's some excellent information, THANK YOU. Looking at the horsepower ratings for 71 I can see a 95-horsepower difference depending on which way it's read. I'm guessing GM came up with a clever way to make it look like they were really being environmentally friendly by giving the engine a net horsepower rating that looked lower than customers had become familiar with seeing which was the gross horsepower number. And based on your experience I can only assume the horsepower was even worse by 74. THANKS FOR SHARING THE INFO!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
Scott S. Posted April 11, 2022 Share Posted April 11, 2022 Also keep in mind that quicker times in the quarter mile is more due to transmission and read gear ratios...... If your '70 had a 2.73 to 1 and your '74 has 3.31 to 1 ratios, the '74 will launch faster.... 1 Quote Link to comment Share on other sites More sharing options...
Michael Boyte Posted April 11, 2022 Share Posted April 11, 2022 Compression and gear ratio will make All the difference in the world !!! Quote Link to comment Share on other sites More sharing options...
Searsman Posted April 12, 2022 Share Posted April 12, 2022 My how things change over time... small print says operates on no lead - low lead gasoline,but if not available ,you can use leaded 91 or higher octane... no lead not available?.. exact opposite now... Quote Link to comment Share on other sites More sharing options...
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