930 clacking noise

sunlion · 01-28-2017, 07:48 AM

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.

Ravi

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Rawknees'Turbo · 09:14 AM

Quote:

Originally Posted by sunlion

I don't recall missing a shift but could that cause this damage?

What do the cam lobes look like (are they scored)? If so, maybe the cam oil spray bar is plugged up with coke particles.

kevin930t · 01-28-2017, 09:19 AM

Like my nose back in the 90s

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Rawknees'Turbo · 01-28-2017, 09:32 AM

^^^

Exactly like that, Kev!

slyguy · 01-28-2017, 09:39 AM

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

turbo owner · turbo owner's Garage

Check the head studs while you're in there

xbmwguy · xbmwguy's Garage

The 90s are over?

sunlion · 01-28-2017, 05:31 PM

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)

sunlion · 01-28-2017, 06:12 PM

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.

sunlion · 01-28-2017, 08:40 PM

All the rocker shafts seem to be backed out......

sunlion · 01-28-2017, 08:42 PM

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

quattrorunner · quattrorunner's Garage

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.

slyguy · 01-29-2017, 06:58 AM

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

TurboKraft · 01-30-2017, 10:20 AM

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%.

sunlion · 01-30-2017, 09:01 PM

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?

sunlion · 01-30-2017, 09:06 PM

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.

onboost · 02-01-2017, 09:37 AM

Quote:

Originally Posted by TurboKraft

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%.

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.

T77911S · 02-01-2017, 10:07 AM

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.

sunlion · 02-01-2017, 02:35 PM

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.

unclebilly · unclebilly's Garage

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.