# Severe Oil Usage



## 21553 (Sep 30, 2012)

Hello Guys,

Looking for some help and idea before I actually take it to an engine shop. I have had my car for about a year and didn't get any info on the motor in it. Investigating the block number I found out it is a 1976 455ci. It has Edelbrock Performer heads with a Demon carb. It also was built for nitrous. 

The issue that I am having is that it is using a tremendous amount of oil. It does have a small leak that will leave a couple drops overnight. But I go through a lot of oil and I don't see a great deal of blue smoke. I do see a lot of black smoke with heavy acceleration but always thought this was unused fuel due to running rich or carbon build up not oil. I took it out yesterday for a round trip of around 125 miles and I went thru a 1qt of oil. The engine seems to run good other than using oil.

I have replaced the pcv valve and the gromment. The pcv valve line is connected directly to the back of the Demon carb. Is this a correct place for the pcv to be connected? There is oil in the line and seemed to be a fair amount. There also seems to be a lot of vacuum to the line. I am going to go out and purchase a vacuum gauge to determine the actual number. Could too much vacuum pull that much oil and burn it that fast?

I also did a compression test an all cylinders and found that they all were 240psi. I am not sure of the compression ratio since I don't know the other values to determine. I also not sure if these are actually good numbers but they seem to be good since they were all the same. Anyone out there with a 455? What psi did you measure during your compression test? What is your compression ratio?

I also did a leak down test tonight. I have never done this before and trying to understand the numbers. I used 90psi in and the numbers were as follows:

#1 84psi
#2 82psi
#3 81psi
#4 82psi
#5 84psi
#6 80psi
#7 84psi
#8 82psi

I could hear the air in the valve covers. Do these numbers seem to be out of line? 

Thanks ahead for all that take the time to reply. 

66GTOMN


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## BearGFR (Aug 25, 2008)

Hearing air in the valve covers indicates that whatever leakage there is, is getting past the rings. (It could also be a cracked head or cracked cylinder but if that were the case I'd expect it to be leaking a lot more than what you're seeing.)

Yes, heavy black smoke indicates too much fuel/rich, but that can also 'hide' the gray smoke of oil consumption.
Still, that does sound like a lot of oil. Check all up under the car - better if you can get it up in the air on a lift. If it's leaking that much from somewhere while you're driving, chances are you'll be able to find a "trail" underneath that might give you a general clue as to where it's coming from.

You can't really tell anything about compression ratio by using compression test numbers. Too many things can affect the values, such as cam shaft. Overal, generally your numbers sound "good" though.

Bear


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## 21553 (Sep 30, 2012)

Bear,

Thanks. I don't have access to a lift. I will see if I can get it up on stands and see if I can see anything. As for hearing it in the valve covers my thought was this could be valve stem seals. Could this be the case?

66GTOMN


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## BearGFR (Aug 25, 2008)

66GTOMN said:


> Bear,
> 
> Thanks. I don't have access to a lift. I will see if I can get it up on stands and see if I can see anything. As for hearing it in the valve covers my thought was this could be valve stem seals. Could this be the case?
> 
> 66GTOMN


Only if it's leaking past the valves TOO, and if that were the case you'd hear it a lot more either through the carburetor or the exhaust first. Valve stems don't ever "see" cylinder pressure and valve stem seals are sure not capable of sealing cylinder pressure, even when they're perfect. The function of stem seals is to keep oil from leaking DOWN the stems and into the intake/cylinders/exhaust.

Bear


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## 21553 (Sep 30, 2012)

Bear,

Thanks again. Do you think these numbers are terrible? Or do you think it would be within tolerance?


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## geeteeohguy (Feb 2, 2008)

What do the plugs look like? Oily? Generally, you want less than 10% leakdown. Also, 240 psi compression sounds like a LOT of cylinder pressure. I once had a Pontiac with high compression and I never heard it ping, and it 'ran fine' on pump gas. Used some oil, though. Turned out it had 4 or 5 broken pistons at the ring lands. I would suspect piston/cylinder issues, but check the plugs first. If you have access to a bore scope, you can look inside the cylinders for damage, etc.


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## Rukee (Feb 8, 2007)

My engine had oil issues when I bought it, it passed a compression test but 1 piston was broken between the first and second ring. The morons who had it before me were using cast piston.


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## 21553 (Sep 30, 2012)

The plugs show no oil. I would have expected to see them a little wet from this much oil. I purchased a camera and looked into the cyclinders and didn't really see much other than carbon build up. That is why I went ahead and purchased the leak down tester. I will look into it some more and report back. It does ping a bit on hard excell with pump gas. I am currently running some 110 race fuel in it to get the octane up. No pinging that I can tell but not hitting hard anymore until I find out the issue.


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## geeteeohguy (Feb 2, 2008)

You have taken all the right steps in diagnoising this problem....Very puzzling that there is no oil on the plugs and no leakage, yet oil is being consumed. What about blowby? Is there any/much smoke out of the breathers on accel just idling?


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## 21553 (Sep 30, 2012)

geeteeohguy said:


> You have taken all the right steps in diagnoising this problem....Very puzzling that there is no oil on the plugs and no leakage, yet oil is being consumed. What about blowby? Is there any/much smoke out of the breathers on accel just idling?


geeteeohguy,

There is a small leak somewhere since I do have a spot of oil. I did mention this in the original long post, sorry. I was thinking this would be a rear main leak since these engines are notoriuos for this issue. there is oil on the bottom rear of the engine and on the transmission. Just didn't think it would be this severe and the usage has seemed to have gotten worse. I haven't taken it on this long of a trip as I have the last month. Mostly short trips of 20 miles max until these trips that I notice such an oil usage.

I have a breather on each valve cover and haven't seen smoke or at least haven't notice. I did see some smoke in the valley pan when I removed the PCV to check for vacuum. I do have a lot of oil pressure after warming up I see around 60lbs at 55MPH. Idle is 20+ and accel is 80+. 

I am trying to figure out how to get it on a lift some where so I can take a better look. I am also thinking it might be time for a trip to a shop for an evaluation. I just wanted to learn as much as possilbe myself so I can be as educated as possible. I have searched ,read and watched many things on oil usage.

66GTOMN


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## Rukee (Feb 8, 2007)

Where is the PCV connected to at the engine, not the carb end?
And that hose should have full manifold vacuum, but not dripping in oil. I suspect the location is not right, or your missing a baffle or something.


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## 21553 (Sep 30, 2012)

Rukee said:


> Where is the PCV connected to at the engine, not the carb end?
> And that hose should have full manifold vacuum, but not dripping in oil. I suspect the location is not right, or your missing a baffle or something.


Rukkee,

The PCV valve is in the front in the valley pan and the hose is connected directly to the back of the carb with a 5/16" hose. The brake booster is connected directly to the intake location. There is a great deal of vacuum at both locations but I don't have a vacuum tester to find out the actual numbers. I did try to find one today at the local stores but no luck. If I block the pcv valve the motor will almost die. 

66GTOMN


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## gjones (Oct 8, 2012)

*gottagettagaugea*

I bought a cheap vacuum gauge on line ($25) and had to return it before I even used it (gauge was off 5#). Got another, used it twice, now gauge is off 1#-NO ABUSE, either!!!) Then I saw one at Advance Auto for $19.99. (Any auto parts store should have it). Looked better than the one I got. Go figure. That'll be one of your "must have" pieces of equipment!


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## geeteeohguy (Feb 2, 2008)

I buy stuff like this used at estate sales or flea markets. A 40 year old made in USA gauge or tool is far superior to any new made in China crap part. I almost never buy this stuff new.


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## Rukee (Feb 8, 2007)

It sounds to me like the PCV is sucking up all the oil. For testing purposes only as long as both valve covers have vented caps I would block off the fitting at the back of the carb and do your road test again. I'd be willing to bet that your oil consumption will stop.


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## geeteeohguy (Feb 2, 2008)

I dunno. The valley pan is baffled, and pretty much no oil gets to where the PCV valve picks up. Running without a PCV, even with open breathers, is a great way to start some massive oil leaks due to the pressure in the crankcase.


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## 21553 (Sep 30, 2012)

geeteeohguy said:


> I dunno. The valley pan is baffled, and pretty much no oil gets to where the PCV valve picks up. Running without a PCV, even with open breathers, is a great way to start some massive oil leaks due to the pressure in the crankcase.





Rukee said:


> It sounds to me like the PCV is sucking up all the oil. For testing purposes only as long as both valve covers have vented caps I would block off the fitting at the back of the carb and do your road test again. I'd be willing to bet that your oil consumption will stop.


Rukee and geeteeoguy,

Thanks. Not sure what to do either but I found a vacuum gauge and will report what I see. My other thought was to temporarily put in a compressor filter with a bowl to catch the oil. This way I still have the pcv in and can see how much oil is being pulled through the line. Any thoughts?

I will be taking it to a carshow on Sunday that is 40 miles one way. Will be a good test for it again.

66GTOMN


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## chuckha62 (Apr 5, 2010)

If it were sucking oil through the PCV at the rate you're losing it, you would see oil smoke in the exhaust. Since the PCV is full manifold vacuum, it would pull the oil directly into the combustion cycle.


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## 21553 (Sep 30, 2012)

geeteeohguy said:


> I dunno. The valley pan is baffled, and pretty much no oil gets to where the PCV valve picks up. Running without a PCV, even with open breathers, is a great way to start some massive oil leaks due to the pressure in the crankcase.


I put a new section of hose on it the other day when I was doing the warm up for the leak down test. There is oil in the pcv line already. So after just that short run time there is traces of oil in the pcv. I will get it all back to gether tonight and run a vacuum gauge on the line to see what the pressue is.

66GTOMN


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## geeteeohguy (Feb 2, 2008)

Also, if the PCV is sucking too much oil, as Chucka said, you'd have blue smoke out of the exhaust AND oil fouling on the spark plugs, which you say you don't have. Maybe the Oil Gremlin is draining off oil in the dark of night.


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## 21553 (Sep 30, 2012)

geeteeohguy said:


> Also, if the PCV is sucking too much oil, as Chucka said, you'd have blue smoke out of the exhaust AND oil fouling on the spark plugs, which you say you don't have. Maybe the Oil Gremlin is draining off oil in the dark of night.


It does smoke but it is black or dark. I do see a very small amount of blue at start but driving only black. It is carboned up on the tops of the pistons by viewing with the scope. The spark plugs looked good after this last weekend run. Not wet or black. The local garage I spoke with said it might be running rich due to the high compression. I would think the plugs would show this but no real evidence. It has to be a rich for the amount of smoke that comes during a hard accel. I again am just trying to learn what I can and I do appreciate all of you and your inputs. I am not trying to mislead anyone but just trying to get some help from fellow owners. Hopefully it is not an oil gremiln.


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## 21553 (Sep 30, 2012)

I continue to search and read. I came across a post from someone not using a stock valley pan. Apparently aftermarket valley pans don't have the baffling. So they are suggesting to use one of the following:

https://www.yearone.com/Product/1964-72-gto/al59

Anyone use something like this? I think it can't hurt to try.


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## fasterfiero (Sep 6, 2011)

I'd try a temporary disconnect of the pcv, I would have to agree with others about the amount of oil you are losing, sound like a problem with a piston oil ring or broken land, probably a combination of smaller problems all adding up. My wives last car leaked like a sieve and it was only about 1/2 qt a week with hundreds of miles driven, I would think you are burning a crap load of oil if you do not have huge puddles under the car.


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## 21553 (Sep 30, 2012)

Well I purchased a vacuum gauge and it was around 15in at idle. When I accelerated and held the RPMs up it held around 30in. I guess I was expecting the vacuum to be lower at high RPMs. 

I also went out and found a different grommet that allowed the pcv valve to be lowered in the valley pan. Like shown in the attached picture on the left and my current set was like on the right:

I also purchased a clear tube so I could see what was being sucked up. But before I did this I had my neighbor take my car out for a ride and I followed so I could look at the exhaust under load. I did see a great deal amount of smoke during accel as I have seen while driving. I did notice it being dark but I could see some gray as well. So guessing this was oil as expected.

I removed the gromment and stuck my camera down in the hole. I didn't really see any baffles so maybe the one they installed was an aftermarket version. I installed the clear tube and the new grommet lowering the pcv down in the valley pan. I started it up and notice a small amount of oil pulling up into the tube. Looked to be a very small amount that might have been in the valve. I let it warm up and reved the engine several times and smoke as I have seen more dark than gray or blue. 

I then took it out for a ride trying to the RPMs up and hard accelerations. I notice that the smoke was slowly getting less and less. It never went away but made a great improvement by the time I got home. Probably a 20 mile drive. 

When I returned home the clear hose was clean but compressed a bit since it was weak and hot. The idle RPM was up a bit as well. I then put a new piece of true vacuum hose on and reassembled. It seem this might have made an improvement but won't know unit this weekend for a long trip. I also know that it does pull high RPMs at highway speeds. I did order the special grommet from my previous post. I will install it if it shows up before this weekend. Thanks again for the help as I try and figured this car out. 

66GTOMN


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## 21553 (Sep 30, 2012)

Just wanted to update incase someone else has an issue like this. By setting the PCV down into the valley pan using a grommet that accepted the PCV body instead of just athe nipple. This made an improvement on my drive today to the carshow and back. Same distance pretty much as last week and I didn't use a noticable amount of oil. Still running a bit rich but not nearly as bad. So it appears the old setup was also starving it for air as well. I will be taking the plugs out later this week to see if they tell a story. Then I will be looking for a place to take it in to have the carb adjusted. 

66GTOMN


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## geeteeohguy (Feb 2, 2008)

Lean it out. If you are running rich enough to get black smoke at cruise and while driving, you are washing the oil off of the cylinder walls and are wearing out your piston rings and cylinders. Gasoline is a great solvent and will effectively remove all the oil off of the cylinder walls.....a big 'no-no'. Fix the carb issue before you drive it a lot.


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## 21553 (Sep 30, 2012)

geeteeohguy said:


> Lean it out. If you are running rich enough to get black smoke at cruise and while driving, you are washing the oil off of the cylinder walls and are wearing out your piston rings and cylinders. Gasoline is a great solvent and will effectively remove all the oil off of the cylinder walls.....a big 'no-no'. Fix the carb issue before you drive it a lot.


geeteeohguy,

Will do. I am trying to find a good place to take it to have it looked at. I just don't feel comfortable doing it myself after reading about the Demon carbs. 

66GTOMN


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