Rocker snapped in half 964 engine
 

Hi first post
My lower rocker on number 3 cylinder snapped in half while the engine was running, snapped around the rocker shaft mid way around the circle.
I was hoping that was the only problem however looking up to the camshaft I can see that it's bone dry, this happened 9 months ago but I've only just got round to taking things apart as I've been working away so I've only just found out what was causing the problem.
I know that after 9 months the cam would not be dripping in oil but wouldn't expect it to be bone dry. There's no obvious wear marks on the cam the lobes feel smooth.
I run out of time today to remove the cam covers on cylinders 456 so haven't seen them yet.
Another thing that was unusual was that the rubber cam cover gasket had partially melted onto the engine.
I'm guessing that there's been a blockage to the oil supply to the the left bank, possibly overheating and causing friction to the rockers on their shafts which caused the rocker to break.
There was no problem with the engines oil pressure even at idle with the engine warm I get 2.5 bar and 5 bar by 3000 rpm
I'm guessing a blockage to the cM spray bar?
I'd like to know from any experienced engine builders have you come across this problem before?
My cars dome 111000 miles and had atop end rebuild 11000 miles ago
The rocker on lower number 3 and 2 have walked slightly around a third of an inch to the right
Thanks guys, I'll upload some pics when I get a chance though I've pretty much described the damage here

Not a pro.

But from what I understand, rockers are meant to break first for obvious reasons. Did you retrieve all the pieces out of the engine?

If you suspect the cM spray bar nozzle is blocked, I would remove it and clean it out and re-install or at a minimum test it by placing a cheap HF oil can at the cam tower oil line inlet, block the tensioner side and observe spray pattern.

Honestly, as far as the shafts, what did you torque them to? I hope not spec, it is way too weak for a used cam towers. Spec calls for 11-13. I put 20 ft/lbs, recommended 18-20 dry install no RSR seals on upper. I put on lowers because I am just nervous like that but was not needed. So far bone dry and shafts stayed in place after I installed 964 Cams.

Here is what I went thru:
http://img.photobucket.com/albums/v5...psdqxw2kfl.jpg
http://img.photobucket.com/albums/v5...psnhktrd84.jpg
Yes, my #2 lower shaft was way to the right on one port :eek: and most of the shafts moved due to lack of adequate torque, not to mention the horrid leaks

I assume 11,000 miles ago you did a complete break in cycle, yes?

Oh yeah, welcome aboard. Sorry to read your troubles :-(

Hi Draco,
Thanks for your reply, I didn't do the top end rebuild, the last owner got it done by a vauxhall garage (GM in the states) I'M from the UK, yeh I've done some reading on the subject and have decided to get a kit from the US which locks the rockers in the correct location, combined with the seal kit installed dry and a slightly higher torque on the bolts should hopefully keep the rockers solid and leak free.
But that's after I've solved the problem, although I can't feel any damage to the cam there's obviously been a fair amount of heat build up in there as all of the lobes are dry and I'm sure it'll have caused a breakdown in the hardened surface even if it's not visible, the engine ran for roughly 50 miles with a tappet sound before the rocker broke, I just thought the clearances had gone out slightly.
If I have to take my engine out to fix the spray bar blockage, I don't think it can be done in situ?, then I'm going to tear down the whole thing and rebuild it from the bottom up.
My oil is changed every 3000 miles so I can only think that the spray bar has become blocked by a piece of sealant or similar and if it's happened once it could happen again, heavens knows what's in the engine to have done this, it's certainly not dirty oil.
Thanks again

Oh and yes I got both of the 2 parts of the rockers complete

Yes

You can service in car if similar to the 3.2

I know we share the same sprocket cam bolt

But before that, I would test the sprayers

When you heard the tappet sound, it probably fractured, bent and was hitting the valve covers then finally broke.

As you know, a loose valve gap is better than too tight.

I would take this time to verify timing and chain alignment and more importantly, check each rocker to insure the are moving freely. I was just thinking, I miss-aligned the shaft once and it made the rocker rock solid. Maybe the re-builder did this too???

Btw you are lucky, Nick Fulljames is in the UK, he sells a shaft seal kit there. He must hate us across the pond, never responds to our emails :-P I wanted to buy the kit for me and dozen of my buddies, oh well. I found the better method of 20ft/lbs :eek: heck of allot cheaper to boot.

Hi, thanks
The kit I was looking at is made by turbocraft in the US

TurboKraft Inc : Rocker Shaft Lock Set [901 105 360 TK] - $359.00

The rockers definitely didn't touch the rocker cover, yeh half of it fell into the cover, the other half stayed attached to the rocker shaft, I think the lack of oil was causing the noise.
I'm sure I read your post in the past, your rocker shaft came right out, how did you get on with that , was your cam damaged or did you get away with just putting things back together again? I was hoping that the problem you had was going to be the same in my case, but oil starvation is my issue I'm sure now
Regards
Logan

If you had a blockage in the feed you'd be seeing scoring on the rocker face and cam.
It will happens in seconds if it goes dry.

I was very lucky, I had some blemishes on the rocker and cam lobe but no grooves that I can feel with my finger nail.

http://img.photobucket.com/albums/v5...pswy32kcfy.jpg

http://img.photobucket.com/albums/v5...psfjw4kvsn.jpg

But, it did damage my bushing so I swapped it for a new rocker with bushing in it
http://img.photobucket.com/albums/v5...pshc0o4zy6.jpg

She is an aggressive Street use daily so I was not too worried, if track car I would have changed the cams.

But I could not help myself and opted to do a 964 Cam Shaft swap :D and verify timing, yeap timing on my 3.2 cams were WAY OFF spec. 1.10 & 0.85 :eek:
http://img.photobucket.com/albums/v5...psdenkyys3.jpg
964 Cams :D

Brother Mark, has a point, How is the condition of the cam lobe and rocker face?

HI Logan
I see the top end of the engine was repaired, what was done, rings, guides, valves, chains?

what sealant was used to seal the cam box , or anywhere on the engine on the top end work

from what you have described , the rocker has sezed on the shafts and stoped open, the piston has hit the valve and snaped the rocker, can you get the rocker shaft out OK and check the valve spring hight with the others that are not on lift to see if the valve is bent.

if you take off the small black connecting pipe near No'1 cylinder plug cap that is held with 2 X 10mm spanner size nuts , then get a oil can to force oil into the cam box, you can then check the oil spray bar in there through the intake side, it could be blocked or turned, you should have 1 jet spraying up and 2 spraying down on each cylinder

regards mike

Logan, what is the condition of the timing chain housings, chains, ramps, etc? On the 964, pressured oil goes into the chain housing and then goes through a little "bridge" pipe over to the cam carrier. This might help you determine where a blockage is.

How dry I am
 

Or it looks it to my old eyes. That cam wont be happy either.

Thanks for all of your replies guys, I've uploaded some pics.
prschman
On further inspection there is a very slight groove on one of the cam lobes, it's very minor and difficult to feel but I can see it, also as you can see from the pics the lobes are not shiny silver but have a grey/blue tinge.

Draco
Thanks for uploading your pleased that you only had minimal damage

Mike
It was Nelson Porsche Stockton who did the top end rebuild, don't know if the valve guides were done, the invoice says "replaced all gaskets, seals and piston rings" the invoice is from a vauxhall garage but it appears all they did was remove/reinstall the engine.
I've had a look at the valve height and it appears to be fully seated, same height as the rest.
I will remove the connector block which supplies the cam housing with oil and use my compressor to blow oil through the spray bar.

Red coupe
Thanks I'm aware of how the oil circulates, though I'm not sure of the condition of the chain ramps etc, what I can say is that one or both of the tensioners need replacing as when the engines not been started for a few weeks I get a very short rattle for approx half of a second until the tensioner takes up the slack in the chain

Yes it is dry, also you can see that the rocker gasket has melted to the engine with the heat, also some of the rocker cover studs have come out instead of the nut, the studs seem to be bonded into the cam housing, there's a black sticky substance which seems to have melted causing the studs to come out.
I think costly as this is going to be, I've dodged a bullet as the cam didn't seize which could have wrecked the engine.

Oh my goodness :eek:

I would remove the other rockers and look at those faces as well.

I was wondering what caused the charring, now we know. Sorry to see these Brother, I think your suspicions of a blocked sprayer/s are warranted. Wow a nightmare.

Taking a second look at your pics, I think that is the back side of a lobe, which should not be shinny, FYI.

Can you show the face of the broken rocker?

Draco
I will do when I've removed it, the other half of the rocker is still held in place by the shaft.
It's the tips of the cams which should be shiny, the lobes, as that's where the metal to metal, cam to rocker pressure point is at it's highest, the second pic I posted is of the cam lobe of number 1 cylinder, the third is number 2
The rocker which broke is number 3, I don't want to turn the engine as the cars sat for 9 months with what appears to be no lubrication on the cam bearings and I don't want to cause any further damage,

I'd remove all the spark plugs, and turn the engine by the crank pulley or alternator to see how that feels. Just because it sat for nine months does not mean things are more seized than they otherwise were. You won't make things worse, and you will need to turn the crank to disassemble the top end if - as may well be needed - in order to check and fix things.

I don't suspect a complete blockage of oil to the cam, because if the cam bearings seized you'd have a whole lot more damage. But the blockage you have is bad enough.

Assuming it turns OK, do a leakdown on each cylinder and compare. You may well have a bit of a bend in that #3 exhaust, and if it leaks more than the others (especially the right side), you will need to pull the engine and at least remove that head to deal with the bent valve. If the comparative leakdowns are good, you have probably dodged the bullet, or at least part of it.

At a minimum you will want to pull all the rockers on the left bank to see how widespread the lack of oil was. How are the wear faces of the other rockers? The cam lobes? A blue cam lobe is not a good sign. The big worry here is whether this wore through the surface hardening enough to compromise the lobe. As noted, an unlubricated cam/rocker interface will penetrate the hardening, and when that happens the lobe will wear down very fast. I once saw a lobe which had fins on each side in the lobe's profile, but the center was worn down to the base circle.

Maybe only one of the oiling holes for the exhausts got plugged? But you have to ask, if that happened, where did the debris come from, and is there any more of it somewhere in the oil system waiting to cause mayhem elsewhere.

In any event, the break was most likely not caused by either an overrev/missed shift, or by a flaw in the rocker casting. If it had just snapped from one of those causes all that heat would not have been generated.