glickman

I'm doing a timing belt job on my 95 SC400 and have been trying to find out if its an interference engine or not. 94 is definitely gen 1 non-interference engine and 96 is definitely a gen 2 interference engine, but there are conflicting points on the 95. I have taken my timing belt off and noticed the timing was off and turned the crank over independent of the cam gears and didn't get any resistance, making me think it is non-interference. However, I'm still not so sure and would like some input, thank you.

t2d2

iTrader: (8)

I thought it didn't become interference until VVTi in '98...

The only '95-96 changeover thing I can think of, engine wise, is OBDII spanning those years on different models.

Ali SC3

iTrader: (10)

There has been lots of debate but the general consensus is the switchover happened sometime in 95. late 95's is questionable, early 95's you might have left over 94 stock.
That is from the little information I could find from people who actually owned those years and tore them down, but I wouldn't say it is definitive.

so 92-94 are the older style which use batch injection on the harness (injectors paired together).
in 95 and on, they changed it to sequential injection on the harness and ecu which is why they are not interchangeable with older years unless you swap harness and ecu.
96+ they added obd2.. and this is where everyone assumed the interference switch may have happened, but it turns out it may have happened during that update in early 95 when they made those changes, probably getting ready to lower the emissions before 96 came around. The ls400 got obd2 early, and on those the block is definitely in question on a 95.

Turning the crank over and not hitting resistance is a good sign, you probably have a non interference one then or the valves are just in the perfect spot where none of them are fully extended.. I think there is actually a cam position where you could possibly turn over the crank on a slightly interference motor but I am not positive about that cause it is a very unusual thing to try.

glickman

Thanks for the reply, good to know that they changed the fuel injection, I didn't know about that. I had thought before that OBD 1 meant non-interference and OBD 2 would mean interference, but if that's not a way to tell then I guess the only way would be to check the valves. I gotta wait for a crank and cam holding tool to arrive in the mail to finish the timing belt, so I'm looking to see if there's a way to identify the engine through either the Vin number or the engine serial number on the top of the block. Nothing like waiting for tools to arrive hahaha.

glickman

Apparently the engine switched to interference once the compression ratio was upgraded to 10.4 (ls400 in 95, sc400 in 96). the engine also got skinnier rods. the problem is no one knows for sure when the sc400 uped the compression and some 95 sc400's have been found to be interference engines.

Ali SC3

iTrader: (10)

I don't remember using a cam holding tool on my 2uz but that was a while back. probably better to be safe if it could be interference.
Yeah it is one of those things that never got pinned down to an exact date over the years. I think all 95 are in question whether SC or LS.
I also want to say the upped compression was on some 1995 for both models, I actually think it was hand in hand with the injector and ecu/harness change.
There just isn't very good 1st hand toyota documentation on it for some reason, so everyone assumed it was with obd2, but really I personally think it was when they changed the harness/ecu and that is why some 95's show up on it and some don't cause they are actually late 94's.
The obd2 was added in 1995 early on the LS, probably as a test for the engine they updated with the new compression ratio. The SC got the obd2 port in 1996, but since it did get the harness ecu change in 1995 I would suspect those got the new block as well.

That being said, it is not very definitive and it is still also not clear that those engines are actually interference, just the newer ones have the skinnier rods... which is a whole other debate out there. try looking up if the 2uz is interference and see what it says, its like 50/50 opinion wise but there aren't many legitimate sounding failures due to that... where other engines that are for sure interference like the audi 2.7t... you hear of those bending valves all the time. 2uz's and late 1uz's bending valves is actually hard to find an example of that is legit, at least last time I looked around years ago.
I don't know of a good way to check for the skinny rods without tearing the engine down... but maybe you could take your ecu part number and figure out which category it falls into.
IF all you are worried about is interference or not, it probably is not interference based on what you said earlier as I don't even think the newer ones are interference in actual reality. again, just my observations I could be incorrect like half the people out there are.

glickman

I got the cam and crank holder since I plan on taking off both gears to replace the seals, but now I need a longer breaker bar because they're so stuck on lol. I think you're right about no one still being sure of any of them being interference (aside from the VVTI). When I first started looking into it a lot of people say that they're noninterference up to 1998 where they changed the motor to vvti. I do think it would make sense that it could have changed when they bumped up the compression though.
I did a bit of digging on the 2uz and just like the 1uz where no one knows for sure if its interference or not. The fact that there's no one getting engine damage from a snapped timing belt or slipping is a good sign though, and now that I think about it I haven't heard of a 1uz having that problem either. Maybe even if they are interference engines the amount of interference is so small damage is rare? or maybe the valves are just super thick haha.
At this point I'm just going to finish up the timing belt and water pump then throw the engine back together and see if it starts or not, and if there's valve damage then we can assume the car is interference. and if not then there's evidence that it's not. I'll let you know how it goes.

t2d2

iTrader: (8)

Good, it wasn't my imagination.

Ali SC3

iTrader: (10)

I have actually heard of non vvti 2uz's with belts letting go that were just fine. I have heard conflicting stories about 2uz vvti's though so those could actually be not sure either way.
1uz really haven't heard of a case of it happening even on the vvti, but if it was close the vvti could factor into it.
Basically I would take it all with a grain of salt, If you are at TDC (cam wise) and you turn it over with the plugs out and its silky smooth.. it probably isn't interference.
Now if you are at the service position on the crank which is a little before TDC or after TDC (The other dot can't remember), then you take the belt off and turn the crank.. the valves are not fully extended in that position which is why that is the service position in the actual manual for timing belt jobs on those motors... and you could be slightly interference and make it all the way around on the crank as long as the cams haven't moved which they also tend to do as you are working.
I don't know if they were just being extra careful or what but they do that on motors that aren't even interference so the real answer is no one really knows for sure.

glickman

Im pretty late to post this but I finished the timing belt and water pump job and the car runs great. I even did a compression test to make sure and the car gets good compression, a little low in one cylinder but I doubt it because of valve damage. I'm thinking its most likely a non-interference engine in my car or maybe I just got lucky.