Whether or not a timing chain break is catostrophic is based on whether the 4.0 engine is an interference design or not.
Interference means that if the timing was off so much that a valve was open when a piston is nearing the top of it's travel, there is such little clearance that the piston would hit the valve, bending it and likely damaging the piston as well.
In college I had a '78 Chevy Impala with the 305 cu. in motor and I had the timing chain break. THe engine just stopped, but that engine was a non-interference design. We had to drop the oil pan to clean out the broken parts, install a new chain and sprockets and I was on my way, no worse for wear.
My brother had a Mitsubishi Eclipse that had a timing belt fail at 7K miles due to a defect where oil would drip on the timing belt and cause it to deteriorate. The entire engine had to be torn apart because of bent valves. Fortunately covered under warranty.
Does anyone know the design (interference or not) of the 4.0 engine?
2016 Roush Stage 3 Phase 2 (727hp) Convertible
- Convertible bar, Roush (red) coil covers, blacked out tails, 20% tint