Non interference, does it mean you're safe?

Hi everyone. Been reading that the supra engine is non-interference. Well done Toyota, why risk it. But does that actually mean that if I'm thrashing it and the cambelt goes, nothing is going to break? Or will it still cause havoc somehow but the pistons and valves aren't on a direct collision course?

Just pondering on a sober friday night, that's all

Thanks

On a stock engine you will be pretty safe if it goes. I've seen a cam pulley come off at high rpm due to loose bolt with no ill effects, new cambelt and car went back out 30 minutes later.

Cambelt coming off may damage some of the cambelt cover plastics.

You will run into issues of pistons/valves touching with larger lift cams.

Ah ok. That's actually quite reassuring. Seeing as it does work, I don't see why all manufacturers don't do it. Engine rebuild just because the cambelt snaps or even gets taken out if the balance shaft belt snaps (known issue on evo's), seems a little risky. No longer my concern it seems

Non interference means that with the piston at top dead centre, it won't hit the valves

Yeah I get that, just i was talking to a mate, and he said that he finds it hard to believe that if the cambelt let go at 6000rpm, full boost, nothing bad would happen. Brilliant if he's wrong. One less thing to worry about

Nothing will happen, its been covered before. But if you want to let your cam belt go to 60k, thats another issue lol.

Yeah I get that, just i was talking to a mate, and he said that he finds it hard to believe that if the cambelt let go at 6000rpm, full boost, nothing bad would happen. Brilliant if he's wrong. One less thing to worry about

Thats because he hasnt got his head around the combustion cycle RPMs have no bearing on it if the cam profile doesnt alter (vtec etc) high rpms are (as the name states) increasing the number of revolutions/ cycles in a given time, not changing the travel of the pistons or valvetrain.

Lol we're all on the same page here, but I can see what my mate was saying. Engine going at full whack, boosting away, and then something gives and suddenly the cams and pistons are all flapping about freely. I can see why he'd think that might not end well, even if the pistons and valves couldn't get too friendly with eachother

Worth noting that the vvti is an interference engine, while the non-vvti is a non-interference engine. Not sure if it's the same for the GTE engines, but my IS300 was absolutely an interference engine as the valves and timing belt were replaced at the same time on the service history receipts (and not at the Lexus recommended timing belt interval).

Only ever seen one cam belt break and that was a diesel on startup, which is when there is the most force on the valve system, belts are far more likely to break on idle and low RPM than high due to the valve train loadings anyway.

Worth noting that the vvti is an interference engine, while the non-vvti is a non-interference engine. Not sure if it's the same for the GTE engines, but my IS300 was absolutely an interference engine as the valves and timing belt were replaced at the same time on the service history receipts (and not at the Lexus recommended timing belt interval).

I've just done some more googling to confirm, and the popular consensus is that the non vvti AND vvti gte engines are non interference, it's only the GE vvti that is interference, possible due to higher compression ratios

I think it's to do with the squish area shape of the pistons, but not having any to compare I can't confirm. Would be interested to know if anyone has actually taken things apart and confirmed. I suspect one of the guys from Whifbitz or SRD could tell us for certain.

Changed my cam belt along with new tensioner and idler back in 2012, car has done about about 5-6k miles. Is it worth doing it all again seen as Toyota say 60k or 5 years. It's been 6 years now

I think it's to do with the squish area shape of the pistons, but not having any to compare I can't confirm. Would be interested to know if anyone has actually taken things apart and confirmed. I suspect one of the guys from Whifbitz or SRD could tell us for certain.

I'm at whifbitz next Friday, I'll ask, or maybe even get mine done.

Changed my cam belt along with new tensioner and idler back in 2012, car has done about about 5-6k miles. Is it worth doing it all again seen as Toyota say 60k or 5 years. It's been 6 years now

The belt deteriorates with age so yes I would suggest you have it replaced.

When it breaks is possibly the biggest issue, losing one on a busy motorway isn't fun

Yeah for sure I am, but do you think there's any point in doing the other parts ie, tensioner

For what the parts cost do it all imo

Because it's non-interference, and to avoid potential breakdowns, I don't even run a cam belt.

Because it's non-interference, and to avoid potential breakdowns, I don't even run a cam belt.

It's been a while since I've seen any quality troll posts on the net, this gave me a good laugh.