My 1969 L68 427 just started losing oil. It’s down a qt quickly. No oil leaks except seepage at PCV valve. When starting up a black sooty spot is on the garage floor. Recently had exhaust and intake manifolds off off to super clean it.

Could the pcv be causing this?

 

Hang tight my friend... moderators will help you move your thread to the appropriate section so that you can get the proper feedback and answers to your questions.

 

Moved you here.. good luck

 

Poorly sealed intake manifold will pull oil In from the valley. If this just started after removing and reinstalling the intake manifold I would be pulling it back off.

 

I was afraid of that, thanks

 

The worst offender of course is the famous Wall of China in the rear of the engine's intake manifold. If that area is not cleaned REALLY well then the RTV doesn't stick which then turns into a killer vacuum leak.

The other problem is when there is not enough RTV used to really bulge out and really seal the surfaces. I do not use the rubber pieces made for the valley ends, instead I used pure RTV and then let it skin over and dry completely.

Some folks are using "The Right Stuff" to seal their intake manifolds, it will "work" but removing the intake may be close to impossible after it cures. I personally stick with standard old RTV as I can clean it up and remove it more easily.

My C3 is a 1968 with a 427 and 4 speed as well. I have been very fortunate as my 427 doesn't leak a drop.

 

I always run a bead of sealant at the bottom of the intake runners now after oil was getting sucked into the intake manifold.

 

So we found one of the intake bolts was lose so hopefully this fixes the oil leak issue.

One new question, when I start it up the oil gauge pushes right to 70 and stays there. Shouldn’t it be closer to 30-35? Could it be a bad gauge or something else?

 

Normal with a tight engine (or heavy viscosity oil or both) on cold start, but it should drop to ~30 to 45 at idle and hot. Does it fall from 70 as it reaches operating temperatures?

Do you know what oil pump is in it?

 

It dies not drop, it stays at 70. I do not know what pump is in it. The engine was rebuilt about 15 years ago and 2 owners ago.

 

Black sooty exhaust does indeed sound like it is burning it, lower intake port gasket leak is very common. If tightening your loose bolt does not fix it, run the mentioned bead of silicone on the lower edge of the intake ports.

What weight oil do you have in there?

70 is normal for cold oil, it gets very thick.
But it should drop to ~30-35 at idle once warmed up.
As you rev it, warm, it should climb up to ~70 at "X" rpm.

If you have 10-30 oil in it, and tell us at what rpm it reaches 70 when warm, the group here can probably tell you whether someone put a high volume pump in there, or not. Which is common, and you do not need, on a street motor. It is another old racer myth.

If you have one in there, warm it up carefully before you get on it.

My guess is if it waits til ~4500 rpm hot to hit 60-70 you have the std oil pump in there.
If it hits 60 at ~2500 rpm hot, you have the high volume oil pump in there.

I do have the high volume pump in mine, 'cause it is built for 6500rpm plus.
On the dyno it idled at 50psi cold, 60*F.
30psi hot, 40 by 2000, 56psi by 3200 rpm. And never went over 60psi. 10-30 oil.

With tighter clearances or cold or thicker oil you could easily exceed that.

 

Thanks for all the information. Next weekend will be the next time for me to check out all your suggestions and advice. I will let you know how it goes!

 

As Leigh says it depends a lot on how its built and what components
Oil pressure is built by the restriction of the oil getting past the bearings. I have a flat tappet engine built withthe standard gaps on the tighter end. I run 15W50 or 20W50 as its the easiest high ZDDP race oil in the area. I also run a high volume pump. My oil pressure stays at 70 psi until all the oil is good an hot then it drops to the high 40s at idle and builds again to 70 once its past idle.

As long as you dont have an obstruction there is nothing wrong with high oil pressure. As long as you run the same brand and viscosity you can use it as a tool to judge wear. As the bearing wear you will see a loss in pressure as long as there is no loss in volume. If you lose volume then your rings, seals are letting oil by. Either can be determined by pressure testing and comparing cylinders. If you see oil on your exhaust, but dont confuse it with carbon, then you can lean on a ring issue if you are losing compression or a intake, lifter seal leak if your compression is still consistent.

As for your black spots on your floor they are most likely carbon from being rich at startup and the condensation byproduct of combustion. Oil would be continuously present when the engine is warmed up and you would see the bluish smoke. I would pull some plugs and see how many cylinders and which ones have oil fouling or caking. If you pull the intake you can look down into the intake valves and if they have a lot of oil staining then you know its the seals or a bad gasket seal. IF you dont remove it but resolve the oil issue I would research either sea foam or spraying water into the carb to steam clean the carbon off your valves and the pistons....it doesnt take mush to clean them up.

I had a bad intake seal at the heads and I resolved it with No 2 permatex form a gasket sealant with a thin coat on both sides of my intake gaskets. Black RTV at the water ports....never an issue again. Gaskacinch works as well too




edit to add a china wall leak wont suck air but will give you a nasty and messy leak down the back of your motor. You would have puddles if the china wall was an issue. Your description is most likely the intake manifold at the heads leak that every suggested before I chimed in

 

^^^THIS^^^
fully agree on the right stuff conundrum. relabel it stuck tight.