| [GMCnet] Tid Bits. Should we be concerned about over reving our Olds engines. [message #340333] |
Thu, 24 January 2019 22:40  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
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The stock 455 that we have is good to 5000 RPM's. The stock 403 is fine to 6000 RPM's. But with the cam profiles that our engines have. There is no reason to go much be on 3900 RPMs. Engine cam profiles are based on many factors. But mostly on how the engine is going to be used, engine cubic inches, final drive ratio, tire diameter, and expected gross weight to be moved. There are more. But these are the main ones. GM had to make a car engine perform the duties of a truck engine. Our engine were built to produce it's peak horsepower, and torque in the 2400, to 2800 RPM range. We drive torque. Not horsepower. Torque is what gets us up that next hill. A torque chart starts at 600 RPM's. And continues to climb till the engine hits it's peak torque RPM point. Then the torque produced will state to drop off. The torque curve chart will be in the shape of a bell. The cam shaft lob profile is the magic that make our engines able to perform to move us along so well. Whenever I start climbing long steep grades. Sift to second. Run the RPM's up to 3700, to 4000 RPM's till I get to the top. And never have the throttle more then half open. I have a personal game I play. In trying to see how high I can get the number of cars that I can get to go around me before I get to the top of the pass. ( GRIN ) When someone says that any RPM's over 3300 RPM's. will just burn the engine up. Due to high piston speeds. That is absolutely, positively not true. Bob Dunahugh 78 Royale
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