Is it the sticker on the air cleaner????
Show me a stock 225 rated at 175hp, we'll talk.
In Australia, the 1969 Valiant Pacer came with a 225 Slant-6 factory-rated at…175 hp! So now can we talk? Great, I'll start: Chrysler South Africa put out 225 Slant-6s factory-rated at 190 hp, too. And all these numbers are more or less bogus. Consider: The 225 1bbl engine's published rating was 145 bhp and 215 lb-ft from 1960 clear through 1971. That's with nominal compression ratios that varied from 8.2 to 8.5, three different camshafts installed with various timing, dozens of different ignition advance curves, dozens of different carburetors, and around 8 significantly different emission control packages. Given that the 170's published power changed from 101 bhp to 115 bhp in 1967 when it was given the 225-sized carburetor and the upgraded camshaft the 225 had received for 1965, those "145 and 215" numbers get pretty hard to trust.
Nevertheless, let's keep torturing them and see what else they'll confess. Here are more realistic numbers from a 1961 225 engine, removed from a new Dodge Lancer, put through a 50-hour break-in, meticulously checked and set to factory specs, and put through well-documented tests in March of 1961. These tests were not done by or for Chrysler; they were done in General Motors' engine engineering department for competitive analysis.
Gross output (air cleaner removed)
Maximum BHP 126.5 @ 3800 rpm
Maximum Brake Torque 210.7 lb·ft @ 1600 rpm
Maximum output (just shy of detonation)
Maximum BHP 115.9 @ 3800 rpm
Maximum Brake Torque 196.9 lb·ft @ 1400 rpm
As-Installed Output
Maximum BHP: 104.5 @ 3800 rpm
Maximum Brake Torque: 189.4 lb·ft @ 1400 rpm
These numbers are notable for a bunch of reasons: they don't conveniently end in nice, tidy, round, advertising-friendly 0s and 5s like Chrysler's 145 (hp) and 215 (torque) figures. The gross BHP figure falls well shy of the published claim. It does, however, match up very well with the "127" rating Chrysler published for the industrial 225 configured and equipped just about identically to the passenger car engine in all the ways that mattered to output. That looks a lot like it was wisely decided that
the only real purpose of a horsepower number on a passenger car is to sell the car, while people specifying industrial engines have a genuine need to know what they're actually getting. And the "as-installed" result looks a lot like the factory rating for the 225 once the SAE Net rating protocol came in for '72, plus a few horses for the better camshaft and minus a few horses for emissions equipment.
Iterate the exercise with the 170 engine: that "101hp" rating for the '60-'66 170 was another marketing fib. The Valiant was marketed as superior to the Corvair and Falcon. 101: just a little bit better than 100. And it rhymes with "fun". An ad man would much rather tell you a car has 101 horsepower than 100, because 101 sounds a lot better.
Now go iterate the exercise with whatever V8 engine you might want to do. It's the same bowl of instant ramen, with a different flavor packet mixed in.