I bought a 1980 l82 a month ago with 24000 miles on it and drove it 1650 miles( from colorado to edmonton alberta, canada) and burned just under a litre of oil during the trip. Not bad for a 31 year old car I thought. I then,3 weeks later drove the car 4 hours to a shop that only works on corvettes,making sure the oil level was perfect before the trip, to get an inspection,headers and exhaust,a compression test,a leakdown test and a few other little things taken care of. They had the car for 2 weeks and I then went back to get it. They told me the car was perfect example of a low milage vette and that both test came out perfect and there were no issues to stop me from changing the cam and intake and spending alittle $ on the motor. Great. So I drive back home(4 hours) and later on, check the oil. It was just under two litres shy of the full line!
I then called the mechanic and he said it could be valve seals, maybe a difference in oil brands and what all. he told me not to be to concerned. Then when I told him I was considering changing the heads also, he advised me not to and that I might be turning it into an "oil burner". And then advised me that if I was stuck on changing the heads, he would recommend the bottom end be redone in light of this new oil burning info. My question is, did he actually do the tests or am I being burned? And where is the oil going? What does rebuilding the bottom end have to do with burning oil and if I replaced the heads, wouldnt the valve seals be replaced , solving that issue ? Doesnt a leakdown also test the valve seals? I am by no means a mechanic but I dont think im retarded. Maybe you guys can tell me if I am, or if im being upsold.

 

You should pull the spark plugs and look at them. They should tell the story.

 

leak down is for the cylinders and normaly not for the valve seals as there not in the cylinders...however by reading the plugs you could get a better idea where the problem lies or at least single out the problem....seals could be the answer but there would be a trace of blue smoke if its seals...leaking valve covers may also be a problem

 

If it's not leaking, it's being burned.

Compression and leak down tests only test the top and second compression rings on your pistons. And of course how the valves are seating. Those tests do not test the piston's oil control rings or the valve seals.

Although 24K miles is considered low mileage, it's the 31 years that have probably taken their toll on those rubber umbrella OEM valve seals. They can be replaced on the car without removing the heads. That's the first thing I'd try.

 

You are either burning it, leaking it or its ending up in the coolant.

Is the oil the color of oil? Check the coolant to see if its milky in color. Two quarts is a lot.

Does it smoke?

J

 

If you don't have any significant oil leaks from the engine area and you don't get any bluish smoke from the exhausts, then the oil is getting ingested somewhere. There are a few possibilities: PCV valve stuck in the 'open' position so that it is always sucking air & splash oil from the valve cover area (the baffle in the valve cover usually prevents this...but only on a properly working PCV valve); intake manifold gasket leak causing some oil from head to seep directly into an intake port (leak into an exhaust port is "possible", but much less likely if you don't have any oil smoke).

You might also get the car warmed up, then park it over some clean cardboard. Rev it up to 2000-2500 rpm for a minute or two, then look for any leak spots on the cardboard. Sometimes, you only get a leakpath to drip once the oil pressure increases from rpm (only leaks while you are driving).

Lastly, did you check your odometer before and after your "repair shop" episode? If it leaked 2 liters of oil while in that shop, someone was driving your car around quite a bit. [And that gives me pause as to whether you should use that shop or not.]

 

First, what kind of dipstick do you have that tells you that you are 2 litres low ? They usually say full and add or something similar so you can add 1 litre to top it up.

Second did you check the oil level at the shop ? Some mechanics will use your car as their daily driver especially if you are 4 hours away, he might have been all over the place with it.

If I ever leave mine overnight at a shop I put a yellow sticky with the mileage on it stuck above the odometer, stops them from joyriding in your pride and joy.

See what the oil consumption is now that you have it home before you do anything.

 

It could be valve seals . A tell tale sign is when you first start it up after sitting and cooling down you get a big puff of blue smoke. Also a puff when shifting gears . Easy fix .

Bill

 

What weight oil are you using?

 

Woodsman: there are several How To books on the small block Chevrolet engine. Any of them will tell you something about these engines. The more you learn, the less you have to depend upon (and pay) others. You should be your own expert when it comes to your car.

 

My bet is the mechanic and his buddies were taking turns taking the car for spins. Happened to me 30 years ago with my '70 Cuda, told the owner I didn't want anyone driving it, went to the body shop to check on the progress and my Cuda flew by in the other lane at about 100mph.

Never happened again, first I tell the shop owner that no one drives it, second I record the mileage, third I put a sticky on the speedo glass with the odometer readings and forth I put in a 3000RPM rev limiter chip in my 6al and cover it with transparent windshield silicone so I can see if it has been removed and lastly I go by at night and see if the car is inside. Nobody but me is going to rev the crap out of my $15,000 motor. If they want to have some fun with a 600HP car they can save up and buy one

 

This problem sounds familiar to me, as i had the same issue. My L82 motor was supposed to have been completely rebuilt with ported heads, gasket matched, etc by a reputable shop. It lost oil at about the same rate as yours, but never smoke out the back and leak down tested fine. The plugs looked good. There were some minor leaks I fixed, but it always seemed to push oil out of the valve cover. I took the car to an engine builder I know and asked his opinion about blow-by. He said, there was no indication anything was wrong, or with excessive blow-by.

Wanting more power and tired of constantly adding oil, I tore it down and found the following:
The head porting was done by an amateur and failed to leave sufficient and consistent port wall dividers. The intake was port matched, but it only had the port opening rounded off to the gasket dimension and not opened and blended into the runner. This failed to make a good seal and was allowing oil to be sucked up from the lifter valley and out the exhaust. The burnt oil inside the intake runners was a clear indication of this happening.

When I got to the pistons, there was no ridge on top of the bore to keep them from coming out the top. Clearly the engine had been rebuilt and clean as a whistle inside. The problem became clear when seven of the compression rings fell off the piston in two pieces. They were obviously not gaped properly and broke on heat expansion.

This engine ran fine and was drag raced with consistent times in the low 14.X range. If it was not for the constant low oil, you would never suspect something was wrong. One Corvette shop told me if the engine was rebuilt for racing, it was probably made loose intentionally and oil consumption expected. I was not getting answers that seemed credible, so a tear down was necessary.

I suspect your engine has something similar wrong, but I hope not. Remember, my engine was passing everyone's test and they were professionals I trusted. Some problems fall out of the cookie cutter symptoms and not as easy to identify. The good news is, my engine had a good block and forged crank to build on with new aftermarket parts. Good luck with yours!!

 

Check your valve covers. Old cork gaskets can leak a lot, ask me how I know. If you can, look from underneath and see if you see oil residue on the heads and block as well as the floor underneath.
They may just need to be tightened but you may just want to replace them.

 

these engines do use oil by comparison to new engines.....some people say a qt per 1000 miles is with in normal boundaries. i bet my engine uses a half qt per 1000 miles

 

Gee easy mike, I thought thats what forums were for. To get the opinions of other people who may have more knowledge or insight into the question that one might have and be able to learn from these people and their experience. We all know that first hand experience outweighs book smarts. The only reason I took my car to a mechanic in the first place was to perform an "out of province inspection" and an appraisal for my insurance wich I cant do. While I had it there, I thought I would save myself some time and get a few extras done so I could enjoy the car before the snow flies and to know if the engine was sound so I could begin teardown during winter to do these few upgrades. I do have the shop manual along with several others.

The car does have a puff of smoke when you first start it, so I did suspect a slight leak on the valve seals. However I did not realize that you could lose that much oil so fast and I thought it was strange that I lost over twice as much oil in a trip that was 70% shorter than the previous one. I guess maybe the seals all of a sudden got way worse,fast, due to the car being used instead just sitting? The oil is still a clean color as is my coolant. Ill pull a plug when I get home and see what the deal is . So losing that much oil could just be valve seals and nothing
else? (That would be nice.) Thanks for all your support!

 

its a chevy. any mechanic should be able to work on it. watch out for the $120/hr corvette mechanic crooks lurking out there.

 

Dear motorhead, im using a regular dipstick. I know thats how low it was because thats how much I had to add to get it to the full mark. I did not check the oil at the shop or the exact milage(dumbass me). Im also using quaker state sae 10 30 oil. Good,bad?

 

The only reason I originally took it to a corvette shop was to get a proper appraisal and out of province inspection and yeah, a little pricey.

 

You should let it sit overnight, no way to get a good reading until all the oil drips down all the way from the rocker arms and every part until it finally fills the oil pan. The hotter the motor is at the time the more accurate the measurement going to be. Filling it cold, and I'm not saying you did you will not get an accurate reading on the dipstick for 1/2 a day or so


Like I said, run it for a while and see how the consumption is now, this stuff doesn't come from books

 

That seems like a lot of oil for the mileage you drove it. I agree with the others who have suggested valve seals, as old as they are they are probably brittle or cracked and not sealing properly. That would be the least expensive route to go at this time.....Tim