wasn't sure where to put this but i am wondering. i read somewhere that chevy started measuring their hp ratings at the wheels?? don't remember where i read that but i was just wondering if that was true or not.

 

nope, they rate the HP at the flywheel.
Some cars, like the 98-02 F-Body's, were under rated from the factory and most of the cars put down the rated HP at the wheels. Maybe that is what you heard mentioned but it was changed a bit in the wording.

 

Yeah, they're rated at the flywheel but using SAE standards (which are a little more pessimistic than why most local dynos use which typically use a slightly different set of standards). THey're also rated with full engine accessories, air cleaner and intake system and full exhaust system. But still, it's a flywheel rating, although it definitely tends to be a much more conservative rating than what you will read about in your typical magazine engine build article.

The LS1 motors in 4th gen f-bodies were well known for being underrated by the factory. Rated a little over 300 from the factory they often put down almost that much to the rear wheels. The factory totally sandbagged on that one- those motors were making every bit as much power as the "350HP" LS1 in their big-brother, the Corvette. The crate motor version of the LS1, rated at 320HP, is likewise a lowball rating- several magazines tested them with headers, no accessories and a high flowing intake system and got almost 400HP at the flywheel.