Warning - 1uz vvti Lextreme/ARP head studs

[ed_ma61]

just a word of warning to anyone running or considering lextreme/ARP heads studs on a 1uz vvti engine...

the studs/nuts are about 10thou too tall under the exhaust cam gear, and foul on the gear teeth. being only 10thou or so too tall, is very difficult to tell that somethings not right, but you WILL be stressing the camshaft as you tighten the bearing caps up, and this can cause a camshaft failure. not that you could even try to run the engine like this, you wouldn't even be able to finish assembling it, but merely cranking down on the bearing caps before discovering there's a problem could be enough to feck everything up for you

im considering junking a camshaft at the moment due to this unidentified problem, and these camshafts aint cheap :Flush:

 

[Arnout]

do you have a picture of the problem?
The stud hits the gear? Same as with the 1UZ non vvti?

 

[ed_ma61]

similar but different to the non vvti...

all the vvti studs are the same length (non vvti has a few shorter bolts) but the ARP washer and 12pt nut are slightly taller than the oem toyota bolt head and washer... this height difference results in fouling of the exhaust cam gear as stated above

 

[Arnout]

same with the 1UZ non vvti.

Compared to:

 

[ed_ma61]

not quite
im aware of the need for the shorter stud on the non vvti engine.
the head bolts on the vvti engine, however, are all the same length, problem is with the height of the fastener...

even with the stud flush with the top of the nut (as in your first pic), it fouls. we need to take 20thou out of the washer and the stud to drop the top of the nut down

 

[XR8tt]

Hmm Good heads up info..
I junked a 2.5 V6 Mazda performance cam in similar circumstances..
Cams break SO easy!!

 

[Lextreme II]

Ed,

Do you have any picture of the studs hitting the cam? VVTi has plenty of room for clearance. Do you have stock or after market cams? Did you use thinner headgaskets? I would love to see some objective evidence that the studs were too long. VVTi engine is the easiest because the cams gear is in front of the engine and no need for shorter studs. This is the first time I hear of this problem. Ed, you stated only one camshaft is bad. If the studs were too long wouldnt both exhaust cams would be affected? Is it studs problem or installation problem/human error? I would love to find out. If my studs cause your cam to go bad, I will be gladly to replace you with a stock exhaust cam.

 

[Smitherz]

"unidentified problem" Your commenting on an unidentified problem? You should figure out what's wrong and talk to the ManuFAcTUre to come to a conclusion about who's fault this was before just posting how bad the product is because of your experience. It's a VERY simple product but you are throwing it into a complicated environment with too many variables to just decide on your own that the studs are what is wrong. Unidentified problem... but hey lets jump out on the forums and spread the word!

 

[rms]

Moral to the story.

Do not assume that ANY aftermarket component is "bolt in".

Production tolerances only need to stack the wrong way and you can be in trouble.

Check 3 times, and then come back tomorrow and check it again !

 

[ed_ma61]

smitherz, jump off the band wagon for a second buddy. im not having a whinge, im not calling libel, im pointing out an issue before it becomes a problem for someone else. its NOT a compicated environment, and it is a very simple product, hence why something not quite fitting is a big problem as its easy to take for granted. jesus, need to relax mate, perhaps turn your font to pink?

it has nothing to do with head gasket thickness or modified cams, it has nothing to do with the length/effective length/installed length of the stud. it is about the clearance between the top of the nut and the bottom of the exhaust cam drive gear.

only one camshaft is bad as the problem was noted installing the first camshaft as the bearing caps werent pulling down correctly

trust me, the vvti has zero room under the drive gear, definietly not 'plenty'. ill take some pics today to clarify.

 

[Smitherz]

Ok. But then if you aren't attacking ARP you should change the thread title to "Advise for 1uz vvti Lextreme/ARP head studs". Then the nice mechanic would explain and show how to work around any issues at hand to share the advise. You stated that anyone that buys ARP studs for their vvti engine can/will have damaged cams as a result.

I see what you are saying about what is going on and it wouldn't take more then a couple minutes to fix the problem while installing. Maybe some people might not realize that the parts are coming into contact if this is a regular occurrence. I can see this happening and if true then it should be noted in the instructions or literature that came with the bolt kit. Maybe you would be so kind to tell ARP or Lextreme about this?

I don't want to tell you no, you can't, you should... but I would suggest machining in a recess into the head so that the washer and the nut is allowed to drop down just low enough to not be in harms way. Looking at your pictures there already is a slight recess in the casting and all you would have to do it drop it down a tiny bit more. Post pix when done!

 

[XR8tt]

Strange I didn't read it as blaming anyone ??
I do know all these tricky bits need clearancing
though...

 

[ed_ma61]

You stated that anyone that buys ARP studs for their vvti engine can/will have damaged cams as a result

and that remains a correct statement if you proceed to install the cam without identifying the fouling. as i said, its in the region of 10thou, so hardly noticeable, yet potentially catastrophic to the cam if you try to tourque it down. my post is both a warning, and contains advice for correcting the issue. i fail to see the problem.

as it is, we took 20thou off the washer on the surface grinder, and linished about the same off the end of the stud. we installed everything again with a 10thou feeler gauge between the stud/nut and the gear, then tourqued the caps down to spec... there's no longer any fouling. we checked the cam to see if it was out of true, it isnt, so thats a bonus, but we're still a bit paranoid given the amount of stress it had, so we'll get it magnafluxed later this week, fingers crossed.

see pic below for a demonstration of the studs relation to the cam gear (stud/nut are covered in the grey arp assembly moly, and the 20thou had already been ground off in this installation shot). also note, it is ONLY the left bank that has this concern as the right bank has the gear offset from the stud position

 

[Arnout]

On the 1UZ non vvti I'm building I mounted the heads to the block without any valves first, to see the clearance on the head studs / cams. You should bolt everything together after you're 100% sure everything fits and has enough clearances. This is just a beginners fault, assumption is the mother of all fuckups. Never assume a kit fits, not even one that comes from lextreme!

 

[SC400TT]

Thanks for the heads up. When we built my motor, we were aware of this potential problem and measaured for clearance. The top of the stud was close, but totally cleared with no problem. We did not have to remove any material off the stud for clearance. I think the message is definitely to be sure to check all clearances, as each engine can be slightly different when they come out of the factory...

Ryan

 

[dulobast25]

good job ed

Good jb ed. There are some who are complaining here that seemingly didnt even know about the issue and regardless of how they feel, you likely saved them some time, trouble or damage which is all anyone should ask for.

 

[ed_ma61]

cheers!... the information is free, do with it as you will. want to get a stick up your butt about it, fine with me!

also got the cam magnafluxed today. all good! and arnout, this was the mock build, and the foul was found on a trial fit. like i said, it's just a function of the foul being in the 10thou region that made it hard to spot. eyeball-o-meter didnt pick it

 

[Zuffen]

Ed,

Have you shaved the heads at all?

I was trying to work out why your's is one of the few engines with the problem.

Assuming it was shaved or the block decked you may have removed just enough to take out the minimal clearance Mr Toyota put there.

You know what it's like you change 1 thing and 10 others yell "what about me?" Hmm, not a bad name for a song.

 

[ed_ma61]

yeah, good idea, except machining wouldnt change the tolerance between washer/nut and cam gear. oem bolts fit no dramas whatsoever. the arp fastener assembly is just a poofteenth too tall though

and mine isnt the only engine, ive since heard of 2uz's having the exact same problem (basically the same heads)

 

[dulobast25]

2uz

how close are the 1u and 2u heads anyways? I always thought the blocks were similar w/ diff material bu the heads were different...