930 clacking noise
 

Few weeks ago, I heard a disconcerting noise from the right side top end, frequency matches engine speed. Checked compression on 4,5,6 - 90, 92, 55. Proceeded with leakdown 1,6,4,3,5: 12%, 100%, 18%, 2%, 9%, 1%. Removed right lower valve cover - found #6 valve adjustment nut off the screw and sitting inside valve cover. Valve screw was loose so valve was closed. Hence leak is on intake side. Removed upper valve cover. Found #6 valve to be tight so valve was not closing all the way. This explains 100% leak on #6. Backed off the screw all the way - found the rocker arm to be sticky, inspected further and noted the rocker arm to be misaligned suggesting the rocker shaft is bent. See photos, one is reference of #4 rocker and the other is #6. Notice more of a gap of the far edge of the mid rocker arm over the shaft against the flange.

I don't recall missing a shift but could that cause this damage? What would be damaged upstream or downstream of this? What should Indo next?

Car is '84, 3.3, K27, otherwise stock, 160k miles, rebuilt at 80k miles sometime back in the '90s.

Ravihttp://forums.pelicanparts.com/uploa...1485621827.jpg
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What do the cam lobes look like (are they scored)? If so, maybe the cam oil spray bar is plugged up with coke particles.

Like my nose back in the 90s

Sent from my SM-N910T using Tapatalk

^^^

Exactly like that, Kev! :D

rocker shaft looks like it's backed out, prob not bent. check your cam lobes rocker surface for sure doesn't take much to beat them up

Check the head studs while you're in there

The 90s are over?

Cam lobes look good to my novice eyes. Repeated leak down with valve screws backed out so valves on #6 are closed - no leak, yay! I'll attempt to remove the rocker arm to inspect it and the rocker shaft. (Motor is still in the car)

Removed sticky rocker arm - rocker arm bearing is scored as is the rocker arm shaft, slightly. Rocker arm on shaft Doesn't feel sticky in my hands but it did in the motor. http://forums.pelicanparts.com/uploa...1485659410.jpg
http://forums.pelicanparts.com/uploa...1485659432.jpg
http://forums.pelicanparts.com/uploa...1485659448.jpg
http://forums.pelicanparts.com/uploa...1485659475.jpg

All the rocker shafts seem to be backed out......http://forums.pelicanparts.com/uploa...1485668370.jpg
http://forums.pelicanparts.com/uploa...1485668391.jpg
http://forums.pelicanparts.com/uploa...1485668411.jpg

Wayne's book mentions the use of RSR rocker arm seals (pg 161). Thoughts on this?

Rocker shaft have to be installed so that the rocker is central to the shaft. That means that one side of the rocker shaft will be a little different on one side than the other in relation to the tower surface in which it resides.

Chris over at Turbokraft has these parts. https://parts.turbokraft.com/collections/911/products/rocker-shaft-seal-set-porsche-motorsport
https://parts.turbokraft.com/collections/911/products/rocker-shaft-lock-set

Rocker shafts do not bend. At all.

Yes, it looks like the rocker shafts have shifted some and need to be reset. If removing and reinstalling all to inspect, then yes, install the Motorsports Rocker Shaft Seals.
If you want to make sure they never shift again, install our stainless Rocker Locks, too.

By the discoloration and lines, I'd say overheating from lack of lubrication.

I'd wager one or more spraybar holes is restricted. You can rig a test by pulling off the banjo at the cam housing oil source, blowing in air, and feelign the flow from each hole. There's 3x holes per cylinder, so 9 total per spray bar. You can usually get a restricted one flowing again by using a hooked piece of stiff wire, paper clip, etc. It's about as good as you can do before pulling out the engine, removing the end plugs, and cleaning out the spray bar 100%.

Thanks for the suggestions fellas. I'll get to cleaning out the spray bars later this week.
My latest finding is that the top of the intake valve on #6 is higher than the others so the rocker make contact with it sooner and hence no free play. The valve is closed as the leakdown is good. Could the valve be broken at the top where the valve keeper sits but yet not slip from the valve guide? Do valves break at that spot?

Anything off in this photo? The top of the valve and keeper seems closer to the flange than the other valves.also, I can depress the top of the valve with a firm bit of pressure. http://forums.pelicanparts.com/uploa...1485842629.jpg

Exactly where I was going on this one... you can also get messier and more visual with it by pumping oil in the spray bar with an oil can and then blowing in air as Chris said. You should see a nice stream from the unclogged holes.

put an allen on the rocker shafts. if you can turn the shaft it is lose.
have you ever looked at the shafts before and noted that they were in the correct place?

cut your oil filter open and/or send your oil off to be analyzed. look for coking particles.
I had mine rebuilt because of coking. its not very much from durabuilt. turbo also seems to run cooler now. back bumper and fender do not get as hot.

synthetic oil and oil changes. let turbo cool before shutting down.

I've been good about letting the Turbo cool. Not using synthetic but using 25/50 given the mileage on the motor, perhaps that's too heavy.
New finding - measured the distance form the top of the valve to the valve cover mating surface on the cam carrier at TDC for each cylinder, #5 is 22mm and #6 is 18 mm. The #6 valve is riding higher for some reason. But it's closed still nice leakdown is minimal. I think the valve is broken at the valve keeper or it's somehow sucked up into the head.....weird either way. I'm preparing to drop the motor next week.

In our last chump race with the chump 911 at Spokane, a rocker shaft walked on us which resulted in a big oil leak on the exhaust which got us black flagged at 1:00 AM. We were in good shape to win but the other teams didn't like our smoke screen in the dark...

Clean it up, get some RSR rocker shaft seals, put it back together, you will be OK. Pay attention to the direction of the shafts and order or install in the engine rebuild book so you can get these all in and torqued up. Set your valve clearances, don't over tighten your lock nuts and bob's your uncle.

20w50 is not too heavy if ambient temps are above about 17 degrees F (no joke - people think it is a summer only oil, but that is not accurate) for an aircooled engine, but synthetics have much higher flashpoints (resistance to burning/coking), and are much less likely to coke up in the superheated, turbocharger bearing cartridge after engine shutdown. Coke particles created in the bearing cartridge is what clogs the cam spray bars, since the dumbasses at Porsche decided the oil return from the turbocharger did not need to be filtered before it was sent to the crank, rods, cams, etc!

In my opinion, you are making way too much out of the valve stem height differences, considering your good leakdown numbers. There is no way that the valve is broken anywhere, or it would have been sucked into the combustion chamber, and have destroyed the head, piston, cylinder, connecting rod and crankshaft, a long time ago. What you are seeing is perhaps a valve seat that is worn/beaten into the head more than the one next to it, a variation in valve shaft length, etc. Unless Chris pipes up and says I am full of it (:))then I wouldn't even consider pulling the engine for that.

my brother has 140k on his 930. always used synthetic, let it cool before shutting down, changed it often and also use to send his oil out to be tested.
the engine is still in great shape.

I pulled my turbo apart.
the coking was in the body of the turbo. the bearings still looked good and the seals were not bad.
my theory on it is the dirt is the main culprit. that and dino oil. it just bakes onto the body of a hot turbo.

I remember seeing a thread many years ago about the filtering of oil and maybe how to change it.
I think I have seen something about changing the oil return out of the scavenge pump that dumps it into the case so it is filtered before going back into the engine.

RT, you make good points. This is the stuff I don't know - variation in valve stem heights exist. You mentioned the valve seat could be worn which makes sense to me and it sounds like this is not a significant concern given the leakdown numbers. There would be more damage with a broken valve. I'll borrrow my friend JWs proctoscope and take a peak inside the combustion chamber as it put it back together.

I reinstalled the #6 rocker and adjusted the valve correctly at TDC. Leakdown is 40%.

930 clacking noise - update
 

Time for an update......
Found 5 of these.....split valve spring retainers
http://forums.pelicanparts.com/uploa...1489039357.jpg
Had many of these......extra valve shims, 8 or more for each valve
http://forums.pelicanparts.com/uploa...1489039425.jpg
Nothing catastrophic but could have been. Top end done and back on the road. Bit of a mystery as to exactly why and what happened. I'm thinking the unusually high numbers of valve shims, 8-10 instead of 5-6 preloaded the springs causing excessive pressure on the retainers which made them split.

You may have had spring binding with that many shims. Did you have excessive cam lobe wear?

No. The cams were fine but installed SC cams.

What are your impressions of the new vs old cams?

I've only been able to put about 50 miles. It's still pretty lazy under 2500 RPM, its more lively over 3k. I was hoping for more get up and go from a dead stop but that ain't the case. Makes more boost than before so went back to a stock spring. Difficult to assess what the result of the SC cams vs the fresh top end reassembly. Most of the original parts were reused other than 2 new valves. New steel studs and valve spring retainers.

see my post on boost vs RpM.

my power comes in at 4200, full boost is 3200.
I recorded the pull in 1st gear so I could go back and look at the numbers later.

I am REALLY curious if the SC cams bring the power on earlier.

would you be able to check those with the engine in the car or even together?

First gear boost only goes to .4 and comes in late, 2nd, 3rd boost starts at 2700 but I'll spend some seat/film time. Rather look at the road than the gauge

that's why I had to video it.
happens too fast

Never mind what I said earlier - just drove, brief video in 1st shows boost begins at 2600, .8 by 3800; happens too fast otherwise and I didn't have a passenger to film. Will get it dyno'd after 1500 mile valve adjust. But it's definitely less tame with the SC cams - feels much quicker, needs full attention.

Is that with the stock exhaust and muffler?

Rahl

No, it has dual outlet aftermarket unbranded exhaust but stock heat exchangers and K27. Purchased this yesterday: will do the middle set up in the photo and extra iPhone for the gauge http://forums.pelicanparts.com/uploa...1489179235.jpg