UZ Engines: Interference or Non Interference?

[Thermactor]

<- here I am with 130,000 on a timing belt on an interference UZ --- gulp!

 

[cribbj]

Thermactor, unless you're driving a VVTi motor or you've put some wild cams in your motor, you should be OK?

The early 1UZ's are non-interference (stock), and the later ones (VVTi) are interference motors.

My #1 motor is currently sitting in the garage without any cams, and next time I'm home, I'll take some measurements to see just how much valve lift it takes to kiss a piston. These wouldn't be absolute type measurements that someone could use for cam sizing, because I don't have stock pistons, plus my heads have been shaved, but it would still be interesting to see.

If someone has a stock motor on an engine stand they could do the community a big service by popping their cams out and taking these measurements to see how much valve lift it takes before the motor becomes an interference type.

 

[Thermactor]

Thermactor, unless you're driving a VVTi motor or you've put some wild cams in your motor, you should be OK?

The early 1UZ's are non-interference (stock), and the later ones (VVTi) are interference motors.

My #1 motor is currently sitting in the garage without any cams, and next time I'm home, I'll take some measurements to see just how much valve lift it takes to kiss a piston. These wouldn't be absolute type measurements that someone could use for cam sizing, because I don't have stock pistons, plus my heads have been shaved, but it would still be interesting to see.

If someone has a stock motor on an engine stand they could do the community a big service by popping their cams out and taking these measurements to see how much valve lift it takes before the motor becomes an interference type.

My friend, I can tell you for sure that the '95-97 1UZ motors are of the interference design. When I did the crank seals on my sister's '95 LS400, I had to take off the timing belt. For the heck of it I rotated the cam sprockets by hand and, yep, a valve smooched a piston. Rotated it the other way, same story.
Now on my '96 the timing belt was done in '02, 120ish thousand miles ago, but by a Lexus dealer, and they replaced the idler pulleys and water pump while it was under their knife, so I run a lower risk of death by seized pulley than not. I could get away with a new timing belt and nothing else new, and be good for another 50,000 miles, which is longer than I expect to keep the car.

 

[cribbj]

Hmmm, that's quite a little nugget of data you've just shared.

According to the Toyota TIS, for the 95+ engines the compression ratio was upped from 10:1 to 10.4:1, and both the cam timing & lift were modifed. I wonder if at that point, the engine became an interference model?

I think many of us here, as well as from other 1UZ forums have always thought that all the non-VVTi UZ engines were non-interference, although, now that I've searched for it in Toyota's NCF publications, it's actually not mentioned one way or the other. Perhaps it's just been another "Internet Truth" all this time. It's a subject that definitely bears further digging into, however. In fact I'm going to move these last several posts into a new "Interference or Non Interference" thread.

 

[Thermactor]

It was at first thought that the '95-97 was non-interference, but eventually word did get around that it is an interference motor. Another huge disadvantage to the '95-97 owner, I suppose! The '90-94 is smelling like a rose.

 

[stevechumo]

...The '90-94 is smelling like a rose.

With beefier rods, too.

 

[Thermactor]

With beefier rods, too.

Non-interference, beefier rods, thicker cylinder sleeves, lower compression ratio.. the facts just add up.

 

[cribbj]

Anyone have interference info on the early 2UZ's (pre-VVTi)?

 

[krayn]

The latter model ones are still no dud. I have an unopened 96 model motor with turbo pushing 400 wheel hp and no problems. Ran a best of 11.91 @ 117 mph in a 1450kg ute. Fairly safe tune though.. cheers kris

 

[cribbj]

The latter model ones are still no dud. I have an unopened 96 model motor with turbo pushing 400 wheel hp and no problems. Ran a best of 11.91 @ 117 mph in a 1450kg ute. Fairly safe tune though.. cheers kris

Thanks for defending the later motor, but let's try to keep this going on topic... Interference or Non Interference.

 

[jibbby]

Well, I just got my 92 SC4 back yesterday after having the timing belt break at full thottle and then replaced.. Engine now purs again, no head damage.. Idle runs a bit high but that's it, tune up will be coming up next.. I am asking myself now, why ever change the timing belts on the early model uz motors, what's the point? Run them til they snap if no damage will happen, right?..

What's funny is my timing belt was over 10 years old and had atleast 130,000 miles on it.. I had a look at it after broken and it was brittle as I could tear it and or rip it apart by hand.. My belt was really gone..

 

[Cobber]

Long live the 1UZ.

The only down side is breaking down in a dangerous or remote situation.

 

[Thermactor]

Funny story, I just took off the spark valley cover and took a peek at the timing belt. Not good. I see a lot of little cracks running along the BACKSIDE of the belt. It looks horrible. I ordered a new belt from AutoZone and will get it in tomorrow morning. I'll take some pictures and share them this evening.

 

[Thermactor]

Timing belt is off. I took tons of pictures. Now it looks like I'll need to do the crank seal too. Bummer!

 

[Thermactor]

I wish we could edit posts after 30 minutes here.
I'm not happy about the condition of the idler pulleys or water pump. They all have a little bit of in and out play. The belt has cracks along the outside and two of the ribs are stripping on the inside, exposing frayed wires. The belt would not have lasted more than another 10,000 miles.
I guess I'll just put it back together with only a new timing belt and a new crank seal. I don't want to put too much money into this motor.

 

[cribbj]

I wish we could edit posts after 30 minutes here.

It's a standard vBulletin setting. Mods can still edit or make changes for you. Drop one of us a PM if there's something you'd like to add/edit.

 

[JBrady]

Thanks for defending the later motor, but let's try to keep this going on topic... Interference or Non Interference.

John, cannot find my old reference material but quite sure that I read factory details stating the engine went interference on the 1995 LS400 with the increase in compression. Curiously that is also when Lexus changed the timing belt replacement interval from 60k to 90k... go figure. I change my belt at 100k and it was still good for 10k+ miles. Obviousy the VVti engines are interference.

 

[Thermactor]

John, cannot find my old reference material but quite sure that I read factory details stating the engine went interference on the 1995 LS400 with the increase in compression. Curiously that is also when Lexus changed the timing belt replacement interval from 60k to 90k... go figure. I change my belt at 100k and it was still good for 10k+ miles. Obviousy the VVti engines are interference.

Definitely a very interference motor on the '95-97. Mine is back together now and running. While I was down there I drilled and tapped a 1/2" NPT hole in the oil pan for the supercharger oil return. I have to say that reassembly is far more unpleasant than disassembly!

As a side note, the $32 AutoZone belt appears to be very high quality, made in Italy. That sure beats $55+shipping+waiting a while from the cheapest discount Lexus parts dealer. Only drawback is no markings for the crankshaft and cams for alignment. That's all trial and error.

 

[Cobber]

Line up the timing marks and mark the old belt with a paint marker before you remove it lay it along side the new belt and transfer the marks. Done this a million times on other vehicles.

 

[Thermactor]

Line up the timing marks and mark the old belt with a paint marker before you remove it lay it along side the new belt and transfer the marks. Done this a million times on other vehicles.

Good advice, I tried doing it in retrospect with the old belt after it had been removed but the cam and crank marks had all been long worn off and were impossible to find even in very bright sunlight.