Interference Engine?

[fiatslug87]

Is the 4.0 an interference engine, i.e. is the valve travel lower than the highest piston travel?

[Geonovast]

Yes.

[Biotex]

I'm going to disagree. It is not an interference engine. To my knowledge mostly only overhead cam engines which run a timing belt are interference. IE. if the belt breaks, you can destroy a piston and or valves.

If the timing chain breaks on a 4.0L or realistically slips a few teeth, the valves would not hit a piston with a stock cam installed...

 

In fact, if you install a high lift cam, you usually run dished pistons to clearance the valves. I have never seen a 4.0L any other way.

[Geonovast]

I could have sworn I read a few articles back in the day that said it was, but it appears I was incorrect.

[Minuit]

Nope. If the timing chain breaks (it won't) or slips the only thing that will happen is the motor will stall. Bet it's a fun job getting the timing right after that happens.

[cruiser54]

Nope. If the timing chain breaks (it won't) or slips the only thing that will happen is the motor will stall. Bet it's a fun job getting the timing right after that happens.

 

Easy to get it right.

[HOrnbrod]

The Jeep (AMC) 4.2, 4.0, and 2.5 are all non-interference designs. However, the big Rotax single engine on my bike is not. Well, it is in stock form, but if you're running a high-lift cam and the timing belt breaks, you're in a world of hurts. It grenades real fast. :eek:

[54bobby]

not interfierance engines. i drive an 86 3 series bmw and they are interfierance engines. if you break a timeing belt on those cars, you're f'd valves slam into pistons and you're looking at major engine work or replacement. our trucks you just coast to the shoulder, replace the chain and back on the road.

[jeepsouth]

good info to know.