atb

I'm thinking that I might try pulling the intake runner so I can come in through the intake port to see if it gives me any better access to the cylinder than the spark plug hole. I would really like to be able to see the whole combustion area before determining if what the pics shows is a concern.

BC

That line seems to be the piston edge. The lighter grey seems to be the bore itself. You may already know this. So this divot is at the edge of the piston crown. You can even see what looks to be the reflection in the relatively shiny bore of the light coming from your aparatus that is shining on the gouge.

Or... I am completely wrong.

IcemanG17

pull the intake runner....rotate the engine so the intake valve is open and try again....its hard to tell from that pic.....

I am leaning towards pitting of some sort on the piston...but from what? & how could it cause the lifter issue?

Lizard928

Pistons have a stamped marking at bottom for marking tolerance.

What do the rest of the pistons look like?
Has a leakdown or compression test been performed?

brutus

If you get a small foriegn object in a cylinder it will sometimes get embedded in the cylinder head and keep ticking. Other times it might just get blown out the exhaust, but few get so lucky.

atb

BC, you are correct in what you see.

It's just odd to see such a "new" gouge in the piston crown. Someone had suggested that if something got into the cylinder on reassembly, it could make the same noise as what I'm hearing now. This pic would seem to confirm that something actually got in there, but if the pics show the outer cylinder wall and outer piston crown, then the item should be sitting exactly where the gouge is.

It's hard to see, but in the last pic, I zoomed out to show the valve reliefs.

They are in this orientation, with the "X" showing the gouge.



Seems that gravity would cause any foreign debris to settle where the "X" is.

Colin, haven't looked at any of the other cylinders. This is the one that seems to be making all the noise (#4). I'll see if I can get a better look through the intake valve opening. If there's no debris in there, then I'll know the gouge is a red herring and pull the cambox off.

atb

The borescope has a mirror attachment, so I should be able to see the roof of the combustion chamber. The engine still makes noise, so if there was debris that blew out, the sound if it being compacted by the piston isn't the source of the noise. Maybe a quick compression check would be in order.

brutus

Just played the video and that is NOT lifter noise. It is happening too fast the cams rotate at 1/2 engine speed you get a knock everytime the piston is at TDC. And it is a much heavier knock. It ate something. Might have been a washer or a small nut but something got in the cylinder. It even could have been in the intake and got sucked in, it happens.

atb

Greg FTW.

Got the cambox off today.

Immediately turned the cambox on its back and pushed down on all of the lifter buttons. Hard as a rock on all of them. I was hoping to find one that I could still actuate. I then looked down at the top of the head, and sure enough, the gasket was indeed flopped over on installation.

Here's a pic of the head casting, you can see the oil passage to the left of the valve spring in this pic.




The hole in the gasket was toward the front of the head, the single oil port to the rear. You can see the imprint of the oil port on the gasket, and see where the oil pressure tore through it. I guess that explains why all of the lifters were pumped up, there was enough pressure that got through to them. No galling on any of the cam lobes or lifters luckily.



On the underside of the cambox, there is no corresponding oil port to match the port coming through the head, just this little "eyebrow" in the channel.



Seems obvious enough now after teardown.

Looks like I'll be making a call into Precision Motorwerks to order up some gaskets.

Since there was enough oil to pump up the lifters, I'm a little leery that there still isn't something else going on here. Borescope and magnet down the cylinders didn't yeild anything. Its it possible that oilpressure from the gasket restriction would cause the noise, yet still allow enough pressure through to pump up the lifters?

Lizard928

How are the cam lobes and lifter tops?

jpitman2

I once had an SU needle locking screw fall into the manifold on a RRover. I could not turn the engine over with the crank handle (that dates me doesnt it!), but it would start and run fine, WITH A LOUD TICKING NOISE. Took the head off (broke one bolt along the way, flush with the block, but it spun out easily ), and found the screw had been flattened against either the squich area, or a valve. In a 16V 928 the squish is at the top, so I would guess a foreign object would get beaten by a valve head....if thats what it is. Is you endoscope fitted with a light?
jp 83 Euro S AT 54k

jeff spahn

I had something fall in the head of my 32v. Got chewed up and spit out. Found the damage when my head gasket gave up the ghost. Sometimes you get lucky.

atb

They're fine, no damage. I was suprised that when I pulled the lifters out of the box, their tops were covered in oil (as was the cam lobe underneath).




Yes, it has a light and mirror attachment. I tried it with the mirror attachment down the plug hole, but it was difficult to make anything out. I think I need to take a head off another motor so I can adjust the mirror at the proper angle ahead of time.

Tom. M

Sounds like you may have found your culprit... Let's hope that's it....cause the Track Attack is on>>>>>>..May 12.... Get that car ready to roll...

Podguy

You might expect the lifters to be full and still cause a racket. The difference of your finger pushing on them and the cam is a fair large difference. Lack of oil pressure in one area sure sounds like a cause of the problem.