? On Replacing Timing Belt On 2000 Lexus Rx300 With 57,000 Miles.

[code58]

Hard to measure, the pistons do have detents in them for the valves. when we took the highlander engine apart I saw everything, but unforturnately didnt do any measurements. i agree totally with you Roger. I wish Toyota would give us the truth or quit using false info to sell their timing belts early. As for the measurement you would have to measure the highest point of the piston, and then turn the head over and measure the lowest point from the base of the head to the valve extension. The cylinder head gasket would have to be added in for height. here is picture of the valve detentions in the piston...

Thanks for the picture Lenore. I am making the assumption now that all pistons come to the top of the cylinder wall, even though the picture you posted has it a short bit shy. I know I've never seen any that didn't. Correct me if I'm wrong. There are of course a number of things that come into play to make sure you don't have interference under any circumstances. Even valve float at high enough rev could cause interference. The interference could be a RARE possibility, but it would still be in Lexus/Toyota's best interest to list it as interference if it is even possible under any circumstances. I think to even get God's Truth accurate answers to the Q's about I vs NI from the horses mouth (Toyota), might be tough. IF they even respond to the question.

I bet that is the easiest filter install you've ever been involved with! :D

[code58]

link to previous debates on here? Im sure the ES guys are in on this as well

Is it possible that Lexus does not know the answer????? Maybe a letter to Lexus would provide an answer that would be conclusive to all?

Paul- several have asked that question of those that work on them at both Toyota and Lexus dealers and have gotten conflicting information. I'm sure some of them thought they got accurate information (so-to-speak from the horses mouth). Having worked in different dealerships for many years, I am not surprised at this. There are good and bad, knowledgeable and unknowledgeable in every field. I wondered myself, why it was so hard to pin this information down accurately. I believe in a conversation on this subject on this or another Lexus forum a few months back, the issue was, at least to my satisfaction (being a stickler for FACT, that's not always easy to come by), put to rest. Gates site lists the 1MZFE- VVT-I as INTERFERENCE. The non- VVT is NON-INTERFERENCE. The fact that where the valves are in the VVT seems to be where the difference lies. There are those that say they, or someone they know had a belt break break and it did no damage causes them to believe they are non-interference. This will be debated til the end of time, but at least to me, a stickler for fact, that explanation for an engine that is listed as INTERFERENCE by someone who SHOULD know, sometimes does not cause damage when a belt breaks, makes sense, and I accept it.

Now for Artbuc, if you live to see this FINALLY put to rest, you're gonna outlive ALL the rest of us!

I was not clear... I meant writing/enquiring to Lexus, not a dealer or salesman who, unless they have experienced the problem, most probably have never had cause to think about it. Also, while non-VVT engines have a "set" high point and valve extension/protrusion, the VVT engine probably has several possible position of the valves for the high piston points. Of course (joke) the simplest way to find out is to take an old engine, set it on the high piston point, and just force the cams in all VVT positions to push the valves, and see what happens.... But I'll be interested to know the answer, though I have changed my timing belt at 6years (60K miles only!) as recommended, because what's the point in taking the risk? Even if there is no damage to the engine, the inconvenience of breaking down is too great to gamble on/against.

Paul- I would NEVER ask the salesman or even service manager. They don't know anything. It's a shame that those who have asked the people who actually work on them have received conflicting information. That shouldn't be. I MIGHT expect an independent shop that works on all makes not to absolutely be sure of the answer, but a dealer mechanic SHOULD. It's his business to know those things, sadly not always true.

[Karl K]

code58

<Even valve float at high enough rev could cause interference.>

That is correct except the valves would not hit the pistons but each other.

I which case, broken belt or not, the valves would be bend or broken and of course then

the pistons would finish the rest.

Karl

[Dura_Max]

That is correct except the valves would not hit the pistons but each other.

Are you saying the valves could hit each other?? If so, how in the world would that be physically possible??

I was hoping to do this all today, but my re-ring/re-seal kit still hasnt made it here from Utah after 10 days, and the machine shop still isnt done with the heads after 14 days What ever happend to good customer service????

[code58]

code58

<Even valve float at high enough rev could cause interference.>

That is correct except the valves would not hit the pistons but each other.

I which case, broken belt or not, the valves would be bend or broken and of course then

the pistons would finish the rest.

Karl

Karl, I don't claim much of any knowledge in this particular area at all, but aren't the intake and exhaust valves each twins (side by side)? In that case I don't think it would be possible to have the degree of float (if float is even possible with the rev limiters they routinely put in the PCM's today) that would allow the valves to collide. That would be a huge amount of float. Maybe someone has a knowledgeable technical answer to the question. From the picture that Lenore posted of the block without heads, the divots in the pistons appear that the valves appose at an angle.

[code58]

That is correct except the valves would not hit the pistons but each other.

Are you saying the valves could hit each other?? If so, how in the world would that be physically possible??

I was hoping to do this all today, but my re-ring/re-seal kit still hasnt made it here from Utah after 10 days, and the machine shop still isnt done with the heads after 14 days What ever happend to good customer service????

You're not dissapointing us Dura-Max, but your machine shop is!

[Karl K]

code 58,

1. I don't believe valve float is possible with all the limitations deigned into this setup.

2. Since you broad up valve float, the intake and exhaust valves are not running side by side,

they are running opposite one another and in a typical floating condition the intake opens

before the exhaust closes and the two collide.

This is not going to happen in this engine, it is a tame engine.

This is just a picture of what happens when valves float because of over-revving or because of weak valve springs

Karl.

[Dura_Max]

Technically that could be possible with a DOHC 4-cylinder and a timing belt driving two pulleys (one for each cam), although the 4g63t Mitsu engines Im use to running just bend all 16 valves on the pistons, without any VVT.

On this 1ME, the exhaust cam being driven by one drive pully and connected with helical gears to drive the intake cam, it might be possible on one cylinder to have the helical gears timed wrong while going back together, but thats a long shot. Having hydraulic roller lifters should eliminate the chance of float if everything is in correct working order.

code 58,

1. I don't believe valve float is possible with all the limitations deigned into this setup.

2. Since you broad up valve float, the intake and exhaust valves are not running side by side,

they are running opposite one another and in a typical floating condition the intake opens

before the exhaust closes and the two collide.

This is not going to happen in this engine, it is a tame engine.

This is just a picture of what happens when valves float because of over-revving or because of weak valve springs

Karl.

[code58]

code 58,

1. I don't believe valve float is possible with all the limitations deigned into this setup.

2. Since you broad up valve float, the intake and exhaust valves are not running side by side,

they are running opposite one another and in a typical floating condition the intake opens

before the exhaust closes and the two collide.

This is not going to happen in this engine, it is a tame engine.

This is just a picture of what happens when valves float because of over-revving or because of weak valve springs

Karl.

That's what I meant Karl when I said "twins". I probably didn't make it clear enough. I meant 2 exhaust valves side by side on 1 side and opposite them 2 intake valves side by side, as in twins.