Oil consumption

[Red 83]

My '83 C10 has an '84 305 crate motor in it. I have noticed that seems to be loosing a quart of oil about every 2 weeks. I only drive it on the weekends, so it sits during most of the week. There aren't any leaks showing up on the ground, and the oil pan is the only part of the engine that has any sludge on it, and it was like that when I bought it.

What is causing the abnormal oil consumption? I can understand maybe adding a quart between oil changes, but that's just because it's an old engine.
Any ideas?

[codyC10kid]

My guise is that your Rear Main seal is bad...Let me gusse.The oil on the pan is towards the back right by the Flexplate....that would be your rear seal...no oil on the ground,leaks when your driving it,high oil pressure found a weak spot..

[Red 83]

The oil is all over the oil pan (front to back). Almost all of my other trucks over the years has had a rear main seal leak. They always left a puddle.

[78 Chevyrado]

mine leaks the worst from the china wall under the front of the intake manifold.  surprisingly, the is the only chevy small block I've ever had that the rear main doesn't leak a drop so far.

[Red 83]

The rest of the engine is clean. I'm just trying to avoid having to pull the engine, or getting a different engine. It's already on its 3rd engine. I also don't want to keep adding oil every two weekends.

It does smoke some when it starts up. I haven't noticed if its blue or not. That was another question, could this be caused by bad rings/valves causing it to burn the oil?

[454Man]

Valve seals

[78 Chevyrado]

Valve seals

usually smoke on startup is valve seals.  smoke while running is usually rings or WAY BAD valve seals or s combo of the two.

the oil only has two ways to go, an external leak you could see and would make a mess, or out the combustion chamber to the exhaust which doesnt make any mess you can see, except smoke.

Mine leaks both externally and through the valve seals, so I add this at every oil change and its stopped 90% of the external leaking and it smokes probably 75% less at startup and never while running.   

I don't have to add 2 quarts now between 5k mile oil change intervals.  now it's been less than one quart (about a 1/2 quart) between oil changes. being 1/2 quart low means I don't add anything anymore.  I don't add anything till it's a quart low except for on a long trip.

[bd]

Valve seals

usually smoke on startup is valve seals....

True, but valve guides and seals alone probably won't account for 1 qt of oil every 4 - 5 days.  And, you haven't described an external leak that accounts for that much oil, either.

So, remove the spark plugs and keep them in order by cylinder.  If the electrodes are shrouded in coke deposits, your probably sucking oil from the valley past cooked intake gaskets.  If you have EGR, cylinders 4, 6 and 8 will typically be the worst.  While you have the plugs out, run a wet/dry compression check.  Let us know the details of all that you find.  Inspecting the spark plugs and checking cylinder compression will reveal a lot.

If you decide to replace the valve seals, avoid the factory umbrella seals and use Viton positive press-on seals instead in conjunction with the factory-style valve stem o-ring seals that clamp under the spring retainers.

[Red 83]

True, but valve guides and seals alone probably won't account for 1 qt of oil every 4 - 5 days.  And, you haven't described an external leak that accounts for that much oil, either.

So, remove the spark plugs and keep them in order by cylinder.  If the electrodes are shrouded in coke deposits, your probably sucking oil from the valley past cooked intake gaskets.  If you have EGR, cylinders 4, 6 and 8 will typically be the worst.  While you have the plugs out, run a wet/dry compression check.  Let us know the details of all that you find.  Inspecting the spark plugs and checking cylinder compression will reveal a lot.

If you decide to replace the valve seals, avoid the factory umbrella seals and use Viton positive press-on seals instead in conjunction with the factory-style valve stem o-ring seals that clamp under the spring retainers.
[/quote]

Would that RESTORE stuff work to seal up that valley/intake gaskets? To replace the valve seals, wouldn't I need to take the intake and maybe the heads?

[bd]

Would that RESTORE stuff work to seal up that valley/intake gaskets? To replace the valve seals, wouldn't I need to take the intake and maybe the heads?

'Restore' won't hurt, but the only way you'll know if it helps is by trying it.

You can replace the valve stem seals w/o removing the intake manifold and cylinder heads by removing the valve covers and spark plugs, pressurizing each cylinder with compressed air, in turn, and then removing each valve spring and swaping the seals one valve at a time.  But, you have to be careful not to depress a valve once its spring is removed, so as not to drop the valve into the cylinder.  And, you have to be careful not to drop the valve keepers down an oil return hole.  It's time consuming and tedious, but much less work than removing the cylinder heads.

Keep the horse ahead of the cart.  Did you remove and inspect the spark plugs and check cylinder compression?