Rbuzz95 Report post Posted September 3, 2009 I have an intake manifold vacuum gauge on my 454 Chevrolet engine. when going up an incline, is it more efficient to run higher RPM and have higher vacuum or lug the engine with low RPM and 0 vacuum? For example: Engine RPM 2,100 = 5 " vacuum shift out of OD. Increaseing RPM to 2,900 RPM increases intake vacuum to 15 ". I think the engine likes the 2,900 RPM but probably uses extra fuel. Whadd'ya think? Share this post Link to post Share on other sites
wolfe10 Report post Posted September 3, 2009 Carb or fuel injected? What model year chassis? Share this post Link to post Share on other sites
