Camshaft cover defect causing rocker-arm breakage (P1302)?

[xtn]

Originally Posted by insane

Sorry man, car's back together and delivered to the restoration shop for new clam shells and paint. Best I can do is a diagram or two:

Please everybody look at the following pics. Please note the wear pattern of the slipper follower in particular. The diagrams posted by insane show a convex radius pretty much. Mine has a concave area. I don't know if this is normal, or if it was worn that way by the failing cam lobe. I didn't think to look at the new rockers before they were installed.

I wonder which surface began to wear first, the lobe or the follower. I also wonder why the wear indicates the follower seems to be riding on the cam lobe close to its inner edge; that is to say the edge nearest the rocker arm pivot. Shouldn't it ride centered under the lobe such that the follower isn't side loaded so much?

[MikeW]

It's definitely worn badly, I would have guaranteed that anyway. I was surprised someone with a dead cam who said their slipper was ok, can't remember who. Anyway, I have 4 new ones so I'm 100% sure. It was originally a constant radius, now it has a divot. By the way, you rocker broke slightly different that one from another car. Not much, but not at the thinnest point closer to the roll pin.

They both wear pretty much at the same time, well, sort of. Assuming one isn't extremely harder than the other. And it depends on the depth of hardening of each piece. I'd guess the depth isn't as great on the cam. it doesn't have to be anyway. The amount of work being done, the load is spread out over a greater area.

[ZAMMY1]

XTN: the roller's bearing in that lifter hasn't failed, has it?

also, i find that a #54 drill, .055" fits snug in the pierced holes, and the hole that's peeing off side is pierced cockeyed on the tube.
i'm gonna play more tomorrow.
it's 60 degrees at 9:30 pm tonite but it's dark, i have to play with water outside....so says wifey.

i'll see what i can photograph for CARL tomorrow.
sam

[MikeW]

The rocker slipper is worn in that area, closer to the left of the slipper, because as the slipper reaches the nose of the cam upon opening, the rocker angles downward and the contact are changes.

[xtn]

Originally Posted by ZAMMY1

XTN: the roller's bearing in that lifter hasn't failed, has it?

No the roller side is fine.

Originally Posted by 4carl

Originally Posted by MikeW View Post
The rocker slipper is worn in that area, closer to the left of the slipper, because as the slipper reaches the nose of the cam upon opening, the rocker angles downward and the contact are changes.

and that increases the stress on the weakest part of the rocker. carl

It shouldn't. No matter where you apply the downward force, the resultant load at the weak point should be dependant only upon the valve spring force that is resisting its motion.

[MikeW]

By the way, in the 2nd photo you can clearly see the blue from the induction hardening near the roller pin. It's hard to see but blue is also visible on the other side of the rocker near the roll pin used for assembly purposes. Also, yours broke at the bottom side where all that machined relief is there for the spring retainer clearance. No large fillet there, instead a bit of a stress riser. Anyone doing rear serious racing might consider prepping these rockers by shot peening. if you could get the roll pin out (not easy) you could get a better idea of how much metal was removed for the slipper spring. It makes all the critical metal thin.

[xtn]

Mike that rainbow blue discoloration follows the break line. Not entirely visible from the photos, but when you hold it in your hand and can turn it around in the light it is obvious.

xtn

[MikeW]

Originally Posted by xtn

Mike that rainbow blue discoloration follows the break line. Not entirely visible from the photos, but when you hold it in your hand and can turn it around in the light it is obvious.

xtn

Yes, I noticed and I know that's a coincidence for sure. The relief for the valve spring retainer has a dose of it too, at least mine do. Of course the thin areas get hot quicker and there's more mass as the broken piece approaches the main body so the thin is blue and the rest isn't. The intent was to heat treat the pads. Anyway, I'm not sure if that cutoff between blue and gray is that significant or not. I was reluctant to say until I saw my metal expert. Since I was at the track this weekend, I didn't see him. My retired tool and die friend says the blue occurs at 400 deg. At that point, the metal starts to go soft again. Now it still depends on the alloy. It may be still hardening at 400. I don't think this alloy is that special however. But likely 375 or less would be enough. You could submit the broken piece for a spectrographic analysis and find the alloy or its properties at least. Of course you could go into this further and spend some money. I'll ask my other friend for an opinion in the next day or so.

[ZTEC]

Here is a new Rocker just for reference

[Dragon]

Yea, from looking at the new one there is a lot of metal missing off of yours. With that much metal missing and I'm assuming even more off the cam lobe the angle of deflection will be changed. Instead of just lifting the rocker arm it will start pulling at it. That's what caused the breakage. Also any gap that may have formed would cause a impact to happen when they connect kind of like smacking it with a hammer. All in all bad ju-ju, now you've all got me worried about my beast (only 1 year warranty in Japan according to the dealer). I'll have to pull the cam cover once I get back from the Tokyo AutoSalon next week and give her a look over. 10,000kms on the clock so there should be some signs of wear by now from what I've been seeing in the pics. Also more than likely only the outer skin of the metal is hardened, once that is worn threw it'll start chewing threw the soft underbelly pretty quickly.

[tesprit]

I know I will be pulling my valve cover before the warranty is out and maybe earlier if there is any clacking noise noted from the valvetrain. For technical instruction on removing the valve cover as well as working on the entire engine, you can view a PDF of the official Toyota Celica Shop Manual here: http://www.newcelica.org/ Once you are on the site, click on "Tech Info", then once the page opens click on "Manuals", and finally click on "Volume 2". The first section of Volume 2 contains the engine information and specifically the directions for removing and replacing the valve cover. Just make sure you are looking at the specific instructions for the 2ZZ engine. Both Celica engines are covered in this manual at the same time. Valve cover removal/replacement appears to be an easy procedure and it should also be very apparent if the 3rd cam lobe is worn with just a visual inspection.

[ZAMMY1]

some pix:
1, start
2. after manipulating a #54 drill in the orofice to get it to squirt straight, a slight bend.
3. the other side of squirts.
4. the restrictor orofice in the oil feed line of the squirts.
more pix next post.
sam

[ZAMMY1]

cam, etc
sam

[Dragon]

Looks like you got it straitened out pretty good there... I wonder if opening up the restricter just a tiny bit to allow a little more flow would help any. My only worry would be if the slight change in oil pressure could affect the cam change over at all. It probably wouldn't though as I'm sure the oil pressure regulator / bypass valve is already open at those rpms. Also not to keen on the wear patterns on the cam's, probably not a big deal, but the ununiform wear patterns make me wonder to the quality of the cam grind/valve train geometry...

[ZAMMY1]

yes, it MAY not hurt to open it slightly, but it wouldn't take much.
remember, if you double the diameter, you have 4 times the area/flow.
also, i expect to anoint the cams with fresh lube before i reinstall the cover.

i glued the shim/washers onto the rear "trunk" lid for easy reinstallation.
i'm trying to dry out all the water before i put it back together.
sam

[ZTEC]

Originally Posted by ZAMMY1

i'm trying to dry out all the water before i put it back together.
sam

Good write up, We used WD40 and an air compressor to remove any water in the tubes,cracks,valleys etc...

[ZAMMY1]

oh, CARL, the lack of wear may be my choice of oil, or it could be that they weren't that misaligned, or that i don't normally rag it too hard.
or even none of that but it's just that i'm such a nice person....
the bad head parts may have been made on a monday morning.
my misaligned squirt was not #3.

who knows??

[SKYVUE]

This is a note from Carl:
"Friday I'm pulling the VC on my old Elise now Hal's.(skyview) the car runs fine with no codes. The purpose is to see if there is cam wear because the car has 30k+mi on it . When I sold it had 19k with 24+ track days and 4000+ track miles plus it's a 05 so this car has all the risk factors. If the cams are not worn that means that all cars used on the track won't necessarily have bad intake high cams. carl"

Friday we'll see more pictures for the expanding story. My '05 Elise runs extremely well and does not throw codes at me.

--Hal

[MikeW]

Remember, If you dump more oil into the head, it has to be able to drain it back down at the same rate. How does the drain hole(s) look.

By the way, to those with trashed cams, have you found metal in the oil? In the head area? The 2zz drain plug isn't magnetic. I think the Moroso pan is. I don't care for metal to go thru the oil pump and coolers before the filter gets it.

[SKYVUE]

How many Elises/Exiges that have broken cam parts so far?
How many have badly worn cams (throwing codes)?
Has anyone put a matrix of factors (mis-aligned squirters, year of car, track vs street use, mileage etc.)?

--Hal