Engine opened after 380000km, Picture Gallery!!! (was: Oil consumption puzzle)

what kind of oil and fuel have you been using? I'm especially impressed with the lack of deposits on the backsides of the intake valves. Everything looks more or less like I would expect of a used engine.

I would keep an eye on oil consumption for a while; it'll probably go

nate

Do you mean seats or seals? The exhaust seats wouldn't directly cause high oil consumption.

Did you hone the cylinders?

-jim

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You said in the pictures "The rings don't look to be a problem", but they are. If you look at the picture you posted, the gaps in the rings are somewhat lined up.

I don't know about you, but when I install rings, I put the gaps away from each other. This eliminates any possibility of blow-by.

A friend of mine bought a 1966 GTO brand new when he got out of the Army. Kept using oil and blowing blue smoke out of the tailpipe. After numerous trips back to the dealer they finally took the heads off and found just what you have here.

I thought that was an indication of his photography skills. I assumed he turned them so that they could smile at the camera :^) It looks like he changed the rings with out removing the piston from the engine. So he would have to rotate the rings so that the gaps are where he can get at them.

-jim

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Typo (sorry!) The seats are good enough, compression is no problem. But whether the _seals_ were really leaking oil isn't certain either. The dirty exhaust valve stems don't prove the oil came in there (it might have only left the engine there!) So how will I ever know?

No, Jim. As you correctly assumed, I replaced the rings without removing the pistons, and the cylinders only were removed for that purpose.

-- Jos

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Oil was just inexpensive non-synthetic stuff, hardly better than cheapest supermarket quality. Fuel is the standard "Euro 95" and occasionally the cheaper "92" that they sell in Germany. With its knock sensor and hardened valve seats, this engine should run on almost anything.

...

But I still would like to know what caused the oil consumption. Were the valve seats leaking or did the oil come up through the cylinders?

Is there any way to tell this from the look of the different parts?

-- Jos

Ewww. It was the RINGS. That thing is worn completely out!

The cylinder walls are mirror-smooth- they should have a fine-grain crosshatching, or at least some evidence remaining- but there's none at all so there's nothing to retain oil on the wall face and the rings wear out. Also look at the rings themselves- glazed, sludged, and the oil control ring groove full of sludge.

I sure hope you re-honed the cylinder walls, because if you left them smooth as glass like that the new rings will self-destruct in no time due to lack of oiling.

Valve *seats* won't cause oil consumtion anyway- its the valve stems or the guides in the head.

...

So the oil consumption was caused by too much oil coming up between the pistons and the cylinders?

But oil does actually stick to it, if you put some on. Isn't that enough?

I did not, so I probably shouldn't expect too much mileage out of those rings. Well, let's see! Other opinions can also be found:

-- Jos

Hi Jos, I didn't have time to read thru all of that, but it sounded like that discussion was mostly about boring out the cylinders and putting oversized piston & rings in. Honing is something you could have done fairly easily since you had the cylinders out of the engine. I don't know if I buy all the logic behind having a honing to get a good cross-hatch on the cylinders but it does seem to work. One problem it addresses ( among other things ) is that after a lot of miles the cylinders don't wear perfectly round so the new rings don't match up well with old glazed cylinders and honing will help break them in so that they fit.

-jim

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With that much wear on the cylinder walls, that would be my inclination.

A good normal oil control ring in good condition will remove the surface oil from the cylinder leaving only oil held in the microscopic roughness of the surface, which protects the compression rings from wear but doesn't leave a glob of oil on the cylinder wall to burn during combustion. Your old rings, however were worn and had lost tension to the point that they'd "ride over" that film of oil, so it would still be clinging to the cylinder wall as combustion progressed and it would burn.

When you put fresh new rings in an old smooth bore like that, the new oil control ring will scrape that layer of oil off completely and without any fine embedded cross-hatch to retain SOME oil the compression rings will run "dry" against the cylinder wall and will wear out very, very fast.

I didn't read the whole thing, but when I see "... because I'm lazy" in the first paragraph I don't exactly get a warm feeling about the technical merit of the discussion. :-/

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The interesting part comes about 35 lines after the start:

"... actual SAE test results involving deglazing/not deglazing rering jobs, and ditto for ridge reams. It seemed that the compression test figures after 10000 miles were *better* by far for the unhoned engines."

This of course still leaves open the possibility that the rings wear out in

-- Jos