Recently Burning Oil...

[GSTAuthor]

Hey guys,

I've got a 'new to me' 66 C20 on my hands that recently began burning oil and having some signs of excess fuel burning as well. My truck has the 283 SBC without modifications.

I began noticing the oil burning increasing about a month ago and checked out the PCV valve first, which was working properly. Being new to this truck, I haven't tried much but that and I also replaced the breather cap on the oil fill pipe because I figured the original one wasn't exactly working well.

One interesting thing is that when I was putting new exhaust on it, I realized that the heat riser was stuck in the up position and it may have been that way for years with the previous owner. I knocked it into the down position, which resulted in more flow out the passenger's side exhaust. That seemed like a good thing, but would that play any role in what I'm seeing?

I should also note:

1. It seems to worsen as the truck warms up.
2. When I hit the accelerator quickly to rev it up, it chokes out
3. When it does get a good rev, it blows both black and blue smoke
4. I noticed that the passenger side valve cover gasket began mildly leaking blue smoke in the past week.
5. The engine does not overheat.
6. The oil pressure used to be in the mid to slightly below mid range, but now it is slightly above mid.
7. Blue smoke is being pushed out of the oil cap breather when running.
8. MPG is about 10.

Those are a few observations. The truck seems to run and drive fine, but isn't always fun driving around wondering how much smoke you're going to be blowing at the person behind you.

Hopefully we can get some thoughts floating around to talk about.

Thanks,

Ryan

[andyh1956]

My 1st thought is the drain back passages & pushrod openings are sludged up. Pull your rocker covers & take a look. then pull your plugs & see which ones are oil soaked. Sounds like a 283 re-furb is in your near future!

[TJ's Chevy]

Sounds like broken rings to me. I would do a compression check and leak down test. Blue smoke coming out of the valve cover is a severe case of blow by. If you were to pull the dipstick while the engine is running will it do the same thing?

[GSTAuthor]

Originally Posted by TJ's Chevy

Sounds like broken rings to me. I would do a compression check and leak down test. Blue smoke coming out of the valve cover is a severe case of blow by. If you were to pull the dipstick while the engine is running will it do the same thing?

I'll have to do the dipstick check and get back to you. I'll do that.

[GSTAuthor]

Originally Posted by TJ's Chevy

Sounds like broken rings to me. I would do a compression check and leak down test. Blue smoke coming out of the valve cover is a severe case of blow by. If you were to pull the dipstick while the engine is running will it do the same thing?

I checked the dipstick out last night and didn't see any smoke coming out when I pulled it out and the truck was running. Just checking in.

[WOLFMANmike]

Originally Posted by GSTAuthor

I checked the dipstick out last night and didn't see any smoke coming out when I pulled it out and the truck was running. Just checking in.

if you have blue smoke getting out past the valve covers and the oil fill tube in the intake then no amount of engine additive / cleaner is going to help you . the blue smoke you are seeing is a broken oil control ring and old valve seals its time for a tear down

[andyh1956]

The reason I said the engine could be sludged up is cause if the oil can't drain down from the rocker area then when it gets to a level above the valve GUIDE then it will run down the valve STEM into the intake area of the head or into the exhaust. Also, when this area is sludged up the PCV cannot evacuate the blow by in the crankcase & excessive pressure builds up. Very few bolts to remove to check this, and there is ALREADY a rocker cover leaking! 283s are old enough to have been run for yrs with non detergent oil!

[GSTAuthor]

Originally Posted by WOLFMANmike

if you have blue smoke getting out past the valve covers and the oil fill tube in the intake then no amount of engine additive / cleaner is going to help you . the blue smoke you are seeing is a broken oil control ring and old valve seals its time for a tear down

Obviously I want this to be wrong, but I'm prepared for it to be right. It will turn into a winter project.

The only thing I'm wondering is if the engine will have to be pulled out to have work done to it associated with replacing the rings?

[GSTAuthor]

Originally Posted by andyh1956

My 1st thought is the drain back passages & pushrod openings are sludged up. Pull your rocker covers & take a look. then pull your plugs & see which ones are oil soaked. Sounds like a 283 re-furb is in your near future!

I'm going to pull the plugs to do the Marvel Mystery Oil piston soak before anything, just to give it a shot. I'll check the plug state then.

[geezer#99]

Don't jump to conclusions.
Your oil smoking might be caused by fuel wash on your rings. Your carb might be flooding(the black smoke). Oil pressure might change due to change in oil viscosity. Oil/fuel mix.
Change the oil and check for fuel in it.

What pcv are you using?
Is it in a valve cover or attached to the road draft connection at the back of the motor?
.

[GSTAuthor]

Originally Posted by geezer#99

Don't jump to conclusions.
Your oil smoking might be caused by fuel wash on your rings. Your carb might be flooding(the black smoke). Oil pressure might change due to change in oil viscosity. Oil/fuel mix.
Change the oil and check for fuel in it.

What pcv are you using?
Is it in a valve cover or attached to the road draft connection at the back of the motor?
.

Geezer,

The PCV valve is mounted on an elbow coming off the carb and the hose coming off the PCV is mounted to the back of the intake manifold. It should be the hole on the far right of this manifold picture:

http://i.ebayimg.com/images/g/JqEAAO...oZh/s-l300.jpg

My first inkling was the PCV valve, so I did some trouble shooting. I first removed the hose from the valve on the back of the carb. That made the engine idle up a little and also idle much smoother. The valve had good vacuum when exposed to the atmosphere from removing the hose.

Due to that, I thought the hose might actually have a clog in it or something. So I disconnected the hose from the other end and took it off completely. The other end was attached to the backside of the intake manifold as far as I could tell. It's back in there under the distributor. I couldn't get to the clamp on the hose so I just took off the actual mount hose mount instead. It was shaped like a dome with a pipe for the house to mount on and a hole in the top of the dome for breathing.

After I took it off, I pulled the hose off and it was not clogged. I actually got a new PCV valve too, so I tried putting it on. I actually let the engine run idle with no hose and no valve on the carb and it idled even higher being it was a completely open system. It idled too high and was popping a little out the pipes.

Anyways, I put the new valve on, and when I pushed the hose onto the new valve, that actually killed the engine. There was probably not enough vacuum to open the valve, so no air was getting to the carb at all. After that, I just put everything back together how it was originally so the truck could still run.

I will say these things:

The truck has smelled 'gassy' from time to time, but I thought it was maybe just due to the tank being right there behind the back seat.

Also, when I quickly hit the gas to rev it up, it hesitates and sounds like it's going to die before actually revving.

Also, there is definitely black smoke that blows out when I do give it a good rev, along with blue. In general, the more I rev it up, the more it smokes blue, but also gets dusty/blackish.

From what I can tell, I'm getting about 10mpg, which I was told seemed low. That would make your idea seem possibly right.

Any thoughts? If I were to let some oil drain out, what would it look like if it had gas in it?

[geezer#99]

One thought!
Need some pics.
That dome is the old road draft tube connection. The later 283's that were converted to a pcv used that cap. There's a canister/baffle inside under the intake. It's there to only allow vapors into the pcv. That canister can become clogged up with carbon like stuff if the motor has been neglected and had very few oil changes.

Have you looked in the carb while it's running? Any excess fuel?
Also your stumble could be caused by a lack of initial timing.
What's your initial timing?

Fuel in oil looks like small light colored rivers. Put a little gas in some water in a bucket. Looks the same. And you should smell it on the dipstick.

Your only problem might be a poor pcv system. Carb could be good.
A few diagnostics can save you a bunch of money.

[TJ's Chevy]

Geezer brings up some super good points.

[GSTAuthor]

Originally Posted by geezer#99

One thought!
Need some pics.
That dome is the old road draft tube connection. The later 283's that were converted to a pcv used that cap. There's a canister/baffle inside under the intake. It's there to only allow vapors into the pcv. That canister can become clogged up with carbon like stuff if the motor has been neglected and had very few oil changes.

Have you looked in the carb while it's running? Any excess fuel?
Also your stumble could be caused by a lack of initial timing.
What's your initial timing?

Fuel in oil looks like small light colored rivers. Put a little gas in some water in a bucket. Looks the same. And you should smell it on the dipstick.

Your only problem might be a poor pcv system. Carb could be good.
A few diagnostics can save you a bunch of money.

There was definitely sludge under that dome.

Would a good test be to pull the hose off the PCV valve and go for a drive and watch the exhaust?

[geezer#99]

Originally Posted by GSTAuthor

There was definitely sludge under that dome.

Would a good test be to pull the hose off the PCV valve and go for a drive and watch the exhaust?

Wouldn't hurt! Might not show any difference. But try anyway.
Plug it off though so you don't get a big vacuum leak.

To see if there's any oil being pulled thru the pcv hose, I've used clear hose.
Bought at the hardware store in the plumbing section. Only a temporary test. Those clear ones soften quicker.

Are you gonna burn us off some pics?

[GSTAuthor]

Originally Posted by geezer#99

Wouldn't hurt! Might not show any difference. But try anyway.
Plug it off though so you don't get a big vacuum leak.

To see if there's any oil being pulled thru the pcv hose, I've used clear hose.
Bought at the hardware store in the plumbing section. Only a temporary test. Those clear ones soften quicker.

Are you gonna burn us off some pics?

Geezer, what would you like pics of? I can do that, yes.

Also, you're saying I need to take the intake manifold off to get at that canister, right?

Sounds like I have some projects ahead of me:

Remove valve covers to check for sludged up ports.
Remove intake manifold to check for PCV-related sludge.
Check the look of the oil.
Check the look of the spark plugs.

Those are looking like ones I can do on my own. With the help of a friend I can probably do the compression test and leak down test.

Sound about right?

[jtrichard]

"Also, when I quickly hit the gas to rev it up, it hesitates and sounds like it's going to die before actually revving." Sounds like the accelerator pump in the carb ....... Another thing that will suck oil and cause blue smoke on an OLDER engine is bad INTAKE valve seals (O-RINGS)

[GSTAuthor]

Originally Posted by jtrichard

"Also, when I quickly hit the gas to rev it up, it hesitates and sounds like it's going to die before actually revving." Sounds like the accelerator pump in the carb ....... Another thing that will suck oil and cause blue smoke on an OLDER engine is bad INTAKE valve seals (O-RINGS)

Thank you! My brother-in-law and I are prepared to replace the valve seals, which many people are saying is the issue due to more oil burn being present during engine braking.

[geezer#99]

Pics of your motor and pcv set up.
Try the clear hose test first. Don't pull the intake yet.

Another thought!
Now that you're diverting all that heat under the intake by closing the heat riser, maybe that's part of your problem. Too much heat causes stumbles and if the oil seperator plate on the bottom of the intake is seperated or cracked you could be drawing some oil in there.

[GSTAuthor]

Originally Posted by geezer#99

Pics of your motor and pcv set up.
Try the clear hose test first. Don't pull the intake yet.

Got it. I can't promise I'll be able to do it today since Mondays are busy for me, but it'll be next on my list for the truck.

I'll get pics of the engine posted when I post pics of the results.

[geezer#99]

Don't shoot yourself in the foot!!
One thing at a time!
Put the heat riser back where it was.
Test awhile.
Then check out the pcv.

[GSTAuthor]

Originally Posted by geezer#99

Don't shoot yourself in the foot!!
One thing at a time!
Put the heat riser back where it was.
Test awhile.
Then check out the pcv.

Your thoughts behind closing the heat riser? I was thinking I did a good thing by realizing it was stuck in the 'up' position.

[geezer#99]

"Up' as in closed or open?

[GSTAuthor]

Originally Posted by geezer#99

"Up' as in closed or open?

The tab was in the up position when I got the truck. When we installed the new exhaust, we knocked it into the down position, which seemed to improve flow to the passenger side exhaust pipe. The driver's side still blows more smoke though, but it did improve.

[geezer#99]

If it's stuck open, that's good.
I thought it was stuck closed.
It should be free to move though.