Ram, GM, and Ford are keeping the V8 alive

US automakers are bringing back their gas-churning V8 engines as federal regulators relax climate rules.Brandon Bell/Getty ImagesDetroit's Big Three are going back to their roaring V8 roots.V8s were on death's doorstep as federal emissions regulations bore down on automakers.Now, as Washington pulls back on climate rules, the V8 trucks and muscle cars are making a comeback.For years, the growl of a big, manly V8 engine had been fading from US auto assembly floors.No longer.A V8 is a gas engine w