07_V6_Stang

Hey everybody! I found a 1972 Fastback w/ a 351 Cleveland 2-V that I will probably buy (just waiting on funds). My understanding is that in 1972 the 351's were only making about 177 HP due to emissions laws (is this accurate? My dad's 72 mach 1 had a 302 with more power.) Although I don't intend to race, I would like it to at least be more powerful than my 07 V6. Ideally, I would like to be making about 300 HP. By the way, it is the stock engine with 120K original miles. Would it be best to just rebuild the whole thing? Keep in mind I'm on a college budget and body work will have to come first. I know it can be done, but what can I do to get there?

1971mach1

1972 is when they changed the way they measured horsepower. Before 72 it was
at the engine crank. After 72 it was closer to what the HP at the rear wheels is. (there's alot of loss in the transmission and diff)
In 71 your engine was rated at 240HP and they really didn't add much smog equip for 72.

On a budget, you'll gain alot of hp by just going with a 4 barrel carb+intake and a duel exhaust system with hi-flow mufflers like Flowmasters.

Randys66gt

If you really want to know some great stuff about the 351C, Pick up the Chevrolet Performance book!! Thats right, Chevy Perf., it was written by Bill Grumpy Jenkins. He said in the introduction page, there is NO ENGINE that is made that will product more horsepower per cubic inch than a 351C!!! Pretty inpressive for a chevy guy huh!

Starfury

Actually, the SAE net hp rating system altered the way the test was performed, not where the power readings were taken.

Pre-'72, there weren't much restrictions on testing. This is referred to as "gross rating." For a long time, manufacturers would test with open exhaust, no fan, no accessories, and better than ideal atmospheric conditions. This produced inflated performance numbers to help compete in the hp war. A good example is the 289. The C code 289 is rated at 200hp, but in reality, with all accessories and exhaust hooked up, it makes closer to 160hp. Another common trick was to dumb down test specs for monster engines (like the 428CJ and 426 hemi) to help reduce insurance rates.

For all '72 models, testing procedures were mandated by the Society of Automotive Engineers (SAE) specs provided to the govt. This meant all engine had to be tested as they would be fitted in the vehicle, with all accessories and full exhaust, and atmospheric conditions were set by the SAE. It provided much more accurate results.