beatngu Posted October 24, 2007 Share Posted October 24, 2007 I have been told that the 401 gas get's around 8 MPG, and I would like to know what newer engines would fit in it. I am aiming for better gas milage, and my pick-up has a 360 that I could rebuilt if the bolting pattern matches. The truck does not really need a lot of horsepower seem's how it has a 20 speed transmission and 8.15's right? Quote Link to comment https://www.bigmacktrucks.com/topic/3005-engine-switching/ Share on other sites More sharing options...
ThaddeusW Posted October 29, 2007 Share Posted October 29, 2007 My GMC 6000 with a 170HP 350 gasser gets about 5-6 MPG. I bet with some more oomph and a newer engine you could get past 8 mpg. The good news is that Mack did use Chrysler engines. But I don't know if you can still easily find the parts. The R400 was offered with a Chrysler as well as some B models to replace the flathead v8's. Quote -Thad What America needs is less bull and more Bulldog! Link to comment https://www.bigmacktrucks.com/topic/3005-engine-switching/#findComment-14757 Share on other sites More sharing options...
beatngu Posted October 30, 2007 Author Share Posted October 30, 2007 I might just get another 401 to replace it, but would there be anything that I could do to improve milage? I figure putting a new exhaust on it (from headers to tailpipe) would help slightly. Quote Link to comment https://www.bigmacktrucks.com/topic/3005-engine-switching/#findComment-14783 Share on other sites More sharing options...
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