2007 Envoy Denali with 5.3L V8. Engine blows at 140,000. Installed a new crate engine. Lifter failure at 500 mile and 300 miles. GM installed a new engine. Lifter failure ate 300 miles and 300 miles. New computer installed. Lifter goes at 500 miles. Wiring harness over laid. Lifter failure at 300 miles. New harness over laid and rerouted away from coils. Lifters failed again in 1300 miles. In the past 7 months i have driven the vehicle 8 days. 2 new engines and 7 replaced lifters. GM dealer is baffled. Does anyone have an idea on what is causing the problem?