Interferenc or Not

[BigDingus]

Hi all.

I had the misfortune of one of my small timing chains snap.

I'm now looking to fit a new chain plus other bits.

Before I start I'm wanting to find out it the engine in an IS250 is an interference engine or hopefully not.

I did see on Youtube a guy turning a camshaft but I like to bee 100% sure.

[ColinBarber]

I'm 99.9% sure it is an interference engine.

[Linas.P]

54 minutes ago, BigDingus said:

Hi all.

I had the misfortune of one of my small timing chains snap.

I'm now looking to fit a new chain plus other bits.

Before I start I'm wanting to find out it the engine in an IS250 is an interference engine or hopefully not.

I did see on Youtube a guy turning a camshaft but I like to bee 100% sure.

Do you mean an ACTUAL timing chain snapped? Or do you mean accessory belt snapped?

Because I have NEVER heard of chains snapping on these engines and frankly I don't believe it is possible (until I see one myself)... unless the engine already been catastrophically destroyed and chain snapped after rod exited the side of the engine. 

If later, then it is not an issue at all, it only drives accessories, water pump, A/C and alternator... it could snap because maybe one of them or tensioner locked-up. It is not ideal of course and the actual cause has to be determined (those belts can easily last 100k miles, so not exactly common to snap for them either)... and it is important to make sure engine was not overheated as result. Overheated 4GR-FSE (the engine in your car) are junk, they warp heads, blow head gaskets and generally are not repairable.

General rule of thumb - Toyota engines that have chain are interference engines, most of engines of VVTi (all?) are interference engines. I can't find reliable information of whenever 4GR is interference or not, but 2GR is and generally speaking most likely 4GR is interference engine. BUT that is moot point - your engine has to be messed-up in some fundamental way for it to snap the chain and it doesn't really matter whenever it is interference or not, after snapping chain it would be full of junk and not salvageable anyway. There are no circumstances where chain snaps and engine survives, although as I said you probably would be first person in the world to snap chain on 4GR so I assume you just snapped the accessory belt.

Now if you happened to need a new engine (which you 100% will need if you snapped the chain), then I can let you have one for cheap. Even just assuming it just needs chain replaced and there is certainly no other damage to the engine... it would still be cheaper to replace the whole engine, than to replace the chain.

[BigDingus]

Thanks for helping guys.

Ive now removed bank 2 exhaust camshaft.

Ive also checked all the valves and they are in perfect nick.

The only damage apart from the timing chain, are 2 cam followers, now removed and ordered, plus the chain tensioner.

I gingerly rotated the cam and there was no indication of any valve coming into contact with a piston.

Linas. The Lexus mechanics and the 2 storemen had never heard of the secondary timing chain snap. Just my luck.

Im hoping the chain can be split or fitting it will be a nightmare.