interference versus noninterference engine??

Timing chains are more robust than a bike chain. I would not worry about the engine being interference or non with a timing chain.
I avoid timing belts, but more to avoid the changing requirement.

 

41 posts and nobody ended up answering the OPs question?

The reply need be no longer than 2 words; either interference or non-interference.

Guess I'll have to search somewhere else to get the answer.

 

I'm going to have to change my original opinion....if you follow this procedure for installing a cam into the 2ZR-FXE (hybrid) engine, it has you put the #1 piston at TDC and then rotate the cam to line up marks in preparation for installing the chain. I can't see Toyo telling someone to rotate the cam if it were going to hit the piston.


https://f01.justanswer.com/tracker40/51b686e8-3e65-421c-8344-1a6650c8533b_125.pdf

 

Exactly. There are more important things to be concerned about. Follow the engine maker's recommendations for oil & filter changes and rest easy.

About asking a service manager...don't get your hopes up. As I noted above, my old Tundra had an interference engine with a timing belt. The service writer and service manager both told me I was wrong. I had purchased the shop manual, and I had to quote them the section and page number to convince them (or at least quiet them). Toyota has...how many dozens of engine models and variants?...and nobody can know all the details about each. If the owner's manual doesn't list a requirement to change the timing belt (and ours doesn't), forget that section of the engine.

 

I have a 4runner with a similar 4.7L 2UZ-FE V8. The engine is interference, but there's been extensive discussion on the forums about it. Apparently the interference is marginal, so if the belt breaks in many cases it won't damage anything. But out of caution it should still be treated as interference. Of course there are many variations of even just that one engine, with different amounts of power and different VVT configuration, and probably other revisions over the years that we don't know about.

Even with the timing belt, some people have gone double the service interval without a problem. And I can't think of many reports of the belt breaking. The maintenance schedule is extremely conservative (as it should be).

 

Since prius engine is virtually identical to toyota corolla engines 1ZZ-FE, 2ZR-FE (except for being atkinson cycle), and corolla 2006+ all have interference engine, it's very probably that prius engines are also interference engines. Having taken the head off in recent HG replacement Isaw that there isn't much space in the head for valve movements before it intersects the highest position of piston, also confirming that prius engine is interference engine.

 

maybe why so many bent rods

 

The explanation I heard somewhere (possibly from gasketmaster video) is that prius has powerful electric motor spinning the crank instead of a conventional starter motor. So when cylinder is hydrolocked (due to blown head gasket), starter would stall, but the prius motor would simply over power it and bend the connecting rods. Of course banging piston against valves would also probably do that too.

 

The thing is, I haven't seen where damage or skipping of the timing chain has been reported with any of these reports of head gasket and connecting rod damage. So it makes sense to stick with hydrolocking as the explanation there. If the valves are in time, the pistons aren't banging them.

(If the valves do get out of time, I think they tend to suffer the brunt of the consequences. They're a lot skinnier than connecting rods.)

 

Answer:
Officially, all Prius Engines are "interference" engines.

In the real-world.....all car engines are "interference" engines given the right set of circumstances, but this term is only really useful in engines with timing belts.

Observations:

* As mentioned several times, Priuses have timing chains, not belts. If the timing chain breaks, then your biggest problem is not going to be bent valves.

* If your are told that timing chain cover leaks, do NOT get it fixed because (a) it's probably NOT a leak, and (2) getting the repair done at a dealership is only slightly less expensive and invasive as replacing a head gasket.....without being NEARLY as necessary.

* The total number of Priuses in the world suffering from a broken timing chain is about the same as the number of them entering a monster truck show.
I'm sure it happens.
Just not a lot.

 

If you get a loose timing chain on this engine - it's going to implode. It would be more cost effective to find an engine from a wrecker and rebuild that one. Remember, those electric motors has enough torque to propel the car to 80 mph - no telling what it's going to bend, twist and break. Actually replacing something broken is easy; it's the stuff that gets bent or twisted slightly out of tolerance that will be giving you a headache during a rebuild. You may end up pulling the engine several times to get it right.

Here's something for ETC(SS):