Today EricW came by and we swapped the head on his slant since cylinder 5 had low compression. The motor now runs great, but we made an odd discovery when the head was off:



This is a picture of cylinder #6 in his 1983 hydraulic motor. Note the odd brown markings on the bore, the odd layering at the top, and the black texturing. There is a noticeable ridge on the top of the bore, but it is only on about the back 270 degrees of the cylinder wall. The portion of the wall towarfds the front of the motor is smooth. Cylinder one has similar marks and ridges, but much less pronounced.

What are those marks? What are the bands? Why is the ridge only on part of the cylinder wall?

My guesses are the brown marks are rust spot from the oil control rings on the piston from when the motor sat outside for an undertermined amount of time. I don't know what those bands are. I think the ridge is actually due to core shift in the casting process.

Any other ideas?

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Casually looking for a Clifford hyperpak intake for cheap.

The upper bands look like carbon deposits. Usually those deposits extend upward from the stopping point of the top piston ring, but for some reason the piston also appears to be pushing deposits up the bore making a second, higher ring.

Did you use some brake or carburetor cleaner to remove the deposits and check how much of that ridge is from actual bore wear? You won't see core shift inside the cylinder unless it's so bad you break into water as the cylinders are bored after the block is cast.

After running my Valiant's 225 faster than probably ever before and then pulling the head I found a fairly sharp metallic ring ridge. I used a ridge reamer to remove the cylinder ridge so the top compression ring wouldn't smack into the ridge and break the top ring or the piston.

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Joshua

Car ran fantastic on the way home....I've never seen a cylinder like that one. The other bores still had a hint of the cross hatch pattern in them. Just that one was wierd. Nice clean plug though, good compression...

Glad to hear it!

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Casually looking for a Clifford hyperpak intake for cheap.

Ive seen this type of wear pattern before. I used to have work trucks that spent a good deal of time idling. Then the whole fleet went on a road trip of 1000 miles of hwy driving. 2 of them had ring problems after that. This is what they looked like.
Frank

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Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

If the car sat for a long time and water got into the cylinder, maybe the damage would look like that.

Whatever, I've had a lot of engines apart and never saw anything like that.

It is common to find a "double ridge" when the top piston ring is stuck or broken... after that happens, the second ring starts doing all the work.

Was the top ring broken or stuck in the piston groove?
DD

I was thinking broken rings too.

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Official Cookie and Mater Tormentor.

Not that I could see. The engine turned over easy enough without the cylinder head on. That cylinder (#6) tested at 160lbs of compression a month or so ago. Maybe I'll do another test today and see what I get. I have put maybe 3K miles since the last test, and 4K on the engine since I've had it in.

If you have not already done so... pull that piston assembly out and inspect the rings. Sometimes you can simply free-up the set that is there or better yet, install a new ring set onto that piston, hone-out that bore and be "back-in -business".

If the engine is in the car and running OK... keep running it, sometimes stuck rings will free-up with use.
It does not take much water in a cylinder to stick the rings.
DD

Eric- I wonder if #6 had a stuck ring that freed up after you started driving the motor?

From what I know of the motor, it ran fine when pulled from the 83 van, but then it sat outside for some period of time. The inside of the motor was heavily sludged up due to a broken thermostat that allowed virtually full flow of coolant through the radiator at all temperatures, resulting in the motor running very cold. I wonder if a ring didn't get stuck due to the motor sitting outside, possibly with condensation in the #6 cylinder? The carbon itself scraped off with my fingernail, so it wasn't hard and crusty like it had been there a long time. That picture was taken before I scraped it off.

I would be curious about the new compression readings too. Just to see if the head swap fixed the low pressure in number 5 as well as to see what #6 looks like.

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Never got to the compression test. I didn't torque down one of the bolts that hold down the rocker arm shaft.... There was a little racket that started after I got out of a store this morning. I thought maybe some crap got into one of the lifters, and saw the second from aft bolt sticking up. All is well now, and I know the head fixed it as the engine is much smoother than with the old head. I'll get to it sometime this week and let you know.

Ahhh. I thought the valvetrain was a touch noisy yesterday, especially for a hydraulic motor. Glad to hear you caught it, and glad the problem is solved.

Well, I guess if it ain't broke, don't fix it! If you get good compression, keep on driving.

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Casually looking for a Clifford hyperpak intake for cheap.