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Old 11-09-2010, 05:32 PM   #26
rfmaster
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Join Date: Oct 2003
Location: OC CA
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Re: 383 Stroker????

Quote:
Originally Posted by 68 TT View Post
GM was ahead of the regulation by a year or so. Most of the muscle cars were set up to run unleaded fuel and lower octane fuel in 71. That drop in compression is the main reason the HP numbers dropped from 70 to 71. In 72 they changed the way the test was performed to measure HP so the numbers dropped again in 72 even though most of the engines were identical to the 71 version.
Agree - an end of era. LA air was very brown back in those days!

SAE engine HP rating change (Gross vs. Net) also took place during 1971-1972 just to confuse (Joe public) everyone a bit further. Depending who you talked to HP net (according with SAE standard J1349) started around '72 which uses horsepower ratings with production engine on a test stand, complete with stock ignition timing, carburetion, exhaust, and all driven accessories. In other words a very close approximation of how much power an engine will produce when actually installed in the car. Note that driveline losses are not accounted (another 13 to 18%).

Great discussion TT!

//RF
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