fourthmeal

I'm a new member but a long-time lurker. Thanks to all who make this forum what it is, btw. Your advice and ideas have been invaluable in my search for a good LS for myself.

At any rate, I thought I'd just share something I stumbled across, something I've not yet seen here at CL.

This is Gates' own Interference engine guide:

http://www.gates.com/part_locator/in...cation_id=3598

In it, it conclusively states that the 95-97 engines are NOT interference. Considering they make the parts necessary to do a quality timing belt job w/ this car, I believe them.

Also, I work for Identifix, and I've not yet seen a single timing belt failure noted in the 95-97 engine range that also resulted in any further engine damage. So I think we can put this question to bed.

fourthmeal

BTW, has anybody conclusively proven this untrue?

Before I posted this, I spent many weeks playing through the archives (~110 pages on here) and learning. This was just about the ONLY thing that didn't have a definite conclusion from what I read.

LiCelsior

iTrader: (32)

95-97 is definitely interference motor. 90-94 is not.

fourthmeal

Where is the proof?

Gates says it is not. The 98 and up they confirm that it is however.

LiCelsior

iTrader: (32)

well Gates is wrong i guess. the 95-97 LS400s were redesigned with some tweaks from Toyota and it had also squeezed out a little more horsepower. i suggest you searching a little more since you can probably find threads about it.

just a easy search turned this up....
https://www.clublexus.com/forums/ls4...ter-break.html
https://www.clublexus.com/forums/ls4...erference.html

fourthmeal

What I am postulating is that this is a myth. I did search, and those two threads were researched amongst the first. I soon saw that there was not one single example of a 95, 96, or 97 1UZFE engine with damage due to timing belt failure. I think that it might be false information to say it is an interference engine.

For certain, the 98 and up ARE. This is proven.

Edit: It looks like as long as there is not VVT, there is no interference. I'm almost 100% certain that this is true. Can anyone scientifically prove this false? It would be nice to know for certain or not once and for all.

avalon42

iTrader: (1)

From my vague recollection, the 95-97 had flat top pistons, which squeezed a little more compression from the motor. The 90-94 had the piston heads recessed slightly to accommodate the valves.

BTW, what point are you trying to make: that Gates (a belt manufacturer) is correct about internal engine components? I'll stick with what Toyota says, spank you very much.

PureDrifter

iTrader: (10)

you're wrong. try listening to the guys that have been involved with these motors for a good amount of time and accept that you're wrong. gods im tired of people not searching then bringing up that useless Gates sheet as a "NEW" and "IMPORTANT" "FACT."

95-97(96-97 for the SC400) had a head design change, toyota squeezed more compression out of the engines and in the process the engine was changed to an "interference" type motor.

so let's review children, 95-97 are INTERFERENCE, 89-94 are NOT. 98-00 are INTERFERENCE, now listen to me and search some more.

http://us.lexusownersclub.com/forums...dpost&p=349106

https://www.clublexus.com/forums/ls4...r-a-97-ls.html

also, show me a SINGLE shred of evidence showing a 95-97 LS400 owner snapping their timing belt (which, in 5 years of being here i have heard of exactly TWICE, both times resulting in damage) and then by some miracle there being no damage. oh wait, its IMPOSSIBLE. (unless you cut the belt with your motor not running, and don't try to start it after the fact, but that's cheating )

vaughn37

I just had a belt break on another car.and it bent the valves...I do not understand why anyone would make a interference engine

steveski

Maybe by modifying the combustion chamber it was more cost effective than increasing displacement

Agreeing with PD, everything I hear including my Lexus mechanic tells me that my 95 is an interference motor tho.

fourthmeal

First thing's first:

PD, not sure if you are aware of it or not, but you come across to people as needlessly brash and rude. As it is hard to realize internally, you may not realize it but you post defiantly...as if you are entitled for one reason or another. Take this as constructive criticism... People look up to you on CL because you are here a lot. Your post count alone proves this. You've also been around for years, despite being quite young yourself. In fact, since you were legal to drive, if I recall. That is no reason to conduct yourself in a manner like you do though. In fact, being a "role model" if you will, of CL means that you carry the torch, so you should hold your own posts to a higher standard as well.

Moving on:

Actually overwhelming evidence points the other direction. Throughout today alone, I searched for a few hours and found that most people agree that the VVT engine change caused the motor to become an interference engine. Before that, it was a non-interference motor. This comes from people swapping motors, from motor builders, from manufacturers' own websites, and so on.

In fact, here at CL was just about the ONLY place that seems steadfast on the idea that 95-97's are interference.

I think this supports my position:
http://www.geocities.com/supradude117/1UZFEinfo.html

Now I've compiled a large supply of links that match this, mostly from people who have had the same question and arrived to a conclusion based on evidence.

I may not be familiar with Lexus as much as the well-versed veterans here, but I have studied the 1UZ-FE engine in depth for a couple years now. I originally planned on using one of these beauties in a Locost, and put in some major research hours to understand how to do that.

The general rule is that if the engine has VVT of any kind, it IS interference. No other factual evidence that I've uncovered shows that a non vvt is.


http://www.rpmrons.com/lexustiming.html
http://us.lexusownersclub.com/forums...howtopic=43063
http://www.preferredcomponents.com/lexus.php
http://us.lexusownersclub.com/forums...t=#entry275849

Realize of course that Gates is one of the only original parts providers that actually bothers to share this info with us. If they are wrong, a LOT of people are going to be wrong, which is why I feel it is important to find factual evidence rather than speculation. Because hours of research on Google has not netted me proof of damage due to timing belt breaks on these suspect years, I'm after real proof.


The funniest part is that Gates says not until '98; Dayco says BOTH, it has 1/2 of its belts rated from '90-97 (non inteference), and 1/2 rated interference at 95+. Beck Arnley says that from '90 and on, they ARE interference. So, who you gonna believe?


When I pick my LS up, and I have to do a timing belt, the curiosity alone will probably force me to find out for myself.

PureDrifter

iTrader: (10)

thanks but honestly, i have no patience for those unwilling to listen. take it as brash or rude, i care not, but concise and to the point, i am. I make no presumptions about who i am, and will conduct myself on these forums as i see fit provided i don't needlessly lambast someone personally. i am allowed to disagree with you as vehemently as i desire, as long as i don't attack you or your character personally, and such i shall.

LOC feels the same way actually, as does lextreme, and seeing as how those 3 alone comprise three of the largest lexus owner forums in the world, i doubt you severely. most people don't build UZ series engines, those that do know better.

look at the year on that geocities page, the '95 SC400. i specifically stated that the SC400 didn't get the updated head/piston design until '96, it was only there for 2 years. that page is irrelevant. also, those who have used the 1uz in the locost, have iirc used either '89-94 engines (as they are the most readily available/cheap) or '98-00 (as the sump was in the best position, or something like that)

the 2 LOC links are by VMF, who was proven wrong several times over and iirc has changed his tune. even the 2nd page of the link you posted shows sonyman telling him he's wrong, and most aggreeing in that '95-00 LS400's are indeed interference. but even aside from that, you're listening to a member who, at the time, believed the following:
also, Wandawoods posted on the 3rd page of that thread with similar information, incl several links, one of which is a well known UZ series engine builder who confirmed that yes, when you rotate the crank with the cams unbelted, the pistons will make "light contact" with the valves.

also, the 2 other links you posted are just bouncing off eachother, the rpmsron site just lists the preferred components catalog, and the preferred components catalog made a mistake in that they separated the 2 non-vvti 1uz variations (89-94/95-97) with separate part numbers but didnt mark one as interference.

finally, my own '95 repair manual, as well as several other peoples '95-97 repair manuals have ALL stated that it is indeed an interference engine, noting that contact will be made with pistons and valves during a timing belt change/engine work if the timing belt is removed/incorrectly installed.

then there's the following:
-every toyota/lexus Mastertech i've ever spoken to personally has told me the same, '95-97 is interference
-Alldata Repair, one of the top 2 repair information databases in the world has THIS for the '95 LS400 (under timing replacement)


-lastly, the part numbers for pistons between 89-94 and 95-97 are different.

fourthmeal

Fantastic that is all the proof I needed.

I appreciate the effort.

I listen well, but I am stubborn when it comes to just taking people's answers as fact. That's like believing the preacher, instead of the scientific evidence. The information and documentation you took the time to serve to me is exactly what I needed to concede that it IS true and that I am mis-guided.


BTW, sorry to make my first thread a questionable one, but it was bugging me for about a year now. You'll probably come to know me as the "audio guy", as time passes on and when I document my full LS audio build.


Oh yes, forgot to mention, I work with ALLDATA and Mitchell daily as they are my company's competitors! I work for Identifix.

gmacrae

heheh chill guys, forums are all about discussion

I kinda get what fourthmeal is on about, it would be kinda nice to see some evidence, one way or another. Plenty of people say this and that and quote other people. A qualified and experienced Toyota/Lexus tech once told me they definitely DONT interfere - even after i questioned him. I think he was probably wrong, but you see what i mean? It does seem like the ucf20 engine is interference from what most people say, but there's a couple of things i dont get;

1) People talk about the change in piston dish/dome/whatever. Regardless of this, the piston has valve cutouts right? Why would toyota bother making cutout, yet not make them deep enough to avoid any interference? Without the cutouts, is there enough cam lift/duration to make the engine interfere under normal conditions? I wouldn't think so, but could be wrong.

2) There are so many other toyota engines with similar compression ratios, VVT, non-vvt. Silvertop 20v 4AGE for example. More valve lift, more valves, 10.5:1 CR, VVT. Non-interference.

The problem is, these engines are built so damn well. I thought a cambelt that's supposed to do 150,000kms was impressive, but it sounds like they'll usually do at least 200,000! Usually the first cambelt is taken care of because the car is still fairly young. But by the time the second one is going to fail many of these cars will be in the scrapyards.

So, who's got a cambelt replacement coming up? I dare you to cut the old one and crank the engine over

edit: Didnt read that last bit, too busy putting in my 2c. I guess that'll do for proof

JBrady

First of all thanks PD for finding the service manual documentation. When I first saw this thread I was going to do the same but didnt have the time at that moment. I have many many times instructed others that the 95+ UZ is an interference engine.

I did cringe at first as I began reading your reply but I understand (as it happens to me) that you were frustrated by the authoritarian tone of first time poster fourthmeal stating inaccurate information which confuses people as indicated by this thread.

fourthmeal, it sounds like you will have a lot to contribute here and your ready appreciation once solid documentation was shown was mature.

Valve cutouts are not for timing belt failure. They are for clearance at or near top dead center. Intake valves begin opening before TDC and exhaust close after TDC. It is better for efficiency and emissions (some would say one in the same) to have a smooth flat piston top or one with carefully formed shape than to have valve relief cuttouts. The engineers would only do the reliefs if necessary for TDC clearance. Cutting them deeper just to create a non-int engine is poor engineering.


The FE engines have a narrower valve angle than the GE engines. This causes the valves to move more directly towards the pistons increasing the interference per degree of crank rotation. That said I am still surprised if the GE engines are non-interference... again... like this thread... is that confirmed or assumed?