Oil consumption

[ross d]

For you engine gear heads, I’ve developed a pretty good oil consumption problem. I’ll try to set it up:
A second run o-320 A2B, 160hp. Has approximately 1500+ SMOH, about 1200 on the cylinders. I’ve gone from 1qt/10 hrs to 1qt/4-5 hrs. Went into annual and we started looking for all the obvious culprits. All cylinders were high 70’s on compression, stared looking with bore-a-scope and all we could find was #4 had some oil in the cylinder. We pulled #4 and found that both oil rings were stuck. Top compression ring appears ok. Decided since 4 was off we’d pull #2. Rings weren’t stuck but gummy. Bother cylinders exhaust valve and guide were worn. #3 was removed about 300hrs ago and valve and guide were replaced due to low compression. #1 has never been off but we see no problem in compression or in the scope. Both cylinders went to cylinder shop, valves and guides replaced but they would not hone the cylinders because they were nickel. (Don’t know what that had to do)…cylinders went back on with new oil rings. After 8hrs of 2400-2500rpm on 1-2 hr legs I’m still at 1qt/4-5 hrs. My question is: will the new rings never seat because of not honing or am I just not being patient enough. EGT/CYL.Head temp are not hot! 1320/350 on #4. I do not want to top on this engine, new cylinders are extinct anyway, and I have a new O320-B2B on order. How screwed am I?

 

[cubdriver2]

What oil for break in?

Glenn

 

[wireweinie]

Most likely have the wrong rings. Specific type of rings to match with a nickel plated wall. It also requires a special stone to hone that type of cylinder wall.

Web

 

[stewartb]

Were the rings correct for nickel bores? When I built my old engine the nickel cylinders broke in within minutes, literally. When I bought those cylinders they came with pistons installed because guys were damaging the rings during assembly. I don’t know if that’s changed. Anyone bought Titan nickel cylinders lately?

 

[ross d]

I’ll check on the type of rings. My understanding was that the compression ring was the only special one called a plasma ring. That ring was not stuck and we went back together with it in. I’m using Phillips 20-50.

 

[cubdriver2]

I’ll check on the type of rings. My understanding was that the compression ring was the only special one called a plasma ring. That ring was not stuck and we went back together with it in. I’m using Phillips 20-50.

Maybe try some mineral oil?

Glenn

 

[Fortysix12]

I run 6 qrts. any more it blows it out. Curious where you are running yours.

 

[Marc Davis]

If you have one of the scopes that are steerable, have a look at the back of the valves. The best way to do this is to start the turn as soon as you leave the spark plug hole. Both intake and exhaust. Bad guides will show oil caking up on the back.

 

[DENNY]

I have around 1500 on my cylinders and that oil usage is about what I have depending on RPM. What are the CHT's running? Not uncommon for valve guide wear above 1000 hrs that is why the wobble test SB came out. High CHT'S will increase wear. You have been just spoiled by the 10hr/1QT oil use, if she makes good power let it run.
DENNY

 

[skywagon8a]

... All cylinders were high 70’s on compression, started looking with bore-a-scope and all we could find was #4 had some oil in the cylinder. We pulled #4 and found that both oil rings were stuck. Top compression ring appears ok. ..... #1 has never been off but we see no problem in compression or in the scope. ...... I do not want to top on this engine,...

Think about what you have done.
"All cylinders were high 70’s on compression". Therefore all your compression rings are doing their job.

"started looking with bore-a-scope" You saw a little oil, that's normal. The question is how much is normal for your engine?

"#1 has never been off but we see no problem in compression or in the scope." OK so the compression rings are working and there is nothing out of place within the cylinder visually.

Now tell us how you know the #1 oil scraper ring is doing it's job. It has no bearing on compression since it's job is to scrape the oil off the cylinder walls sending it back into the crankcase. If you left the oil ring out completely you would still have good compression.

4-5 hours on a quart of oil is within limits. Not like a new engine, but within limits.

"I do not want to top on this engine" Why? You have already topped 3 of the 4 cylinders.

 

[ross d]

Fortysjx12, I also run at 6qts

 

[ross d]

Yeah Denny, spoiled I am! But we did replace the valves and guides. Temperatures are running cool, I’m going to check if the oil rings are a special ring for the nickel cylinders.

 

[ross d]

Skywagon8a, I guess short of honing I have. I just might need a chase plane with a couple of cases of oil for Idaho this year!

 

[Steve Pierce]

Nickel has a special finish and does not need honing, it is very hard and holds new bore tolerance up to TBO. You oil consumption is not bad, not new engine 8-10 hours but beats the quart every 3 hours on my first airplane I put hundreds of hours on. Could it be that the other two cylinders have gummy or stuck rings as well. Are you getting to be like a little old lady and just want to worry about something instead of fly? 8) Maybe you should come up and play and we will pick on you enough you will not think about your oil consumption. Or I have a friend here who will trade you a C150/150 with a new engine.

 

[cubdriver2]

Put some MMO in the oil and gas

Glenn

 

[KevinJ]

http://www.mmca.com/fpc/Documents/S...ent flush procedure (Ed Kollin, CamGuard).pdf

Anybody had success with this?

 

[Steve Pierce]

http://www.mmca.com/fpc/Documents/S...ent flush procedure (Ed Kollin, CamGuard).pdf

Anybody had success with this?

Ed Kollin is a pretty sharp guy.

 

[55-PA18A]

What does your oil look like? How quickly does it turn black after an oil change. I had a broken ring that allowed blow by. Oil turned black within an hour after oil change and used a quart in 4 -5 hours. Compression was good until one day it wasn't. Pulled cylinder and found broken ring.

 

[ross d]

LOL, Steve, I wouldn’t know how to act if you weren’t picking on me! I do want to come up and play but was thinking you would be so afraid of putting a ding on your new plane or getting it dirty you’d wimp out on me! Ok, 4hr/qt it is. I’m going to keep pouring oil in until to new motor arrives. They said late April but didn’t say what year!