PCV vs. oil mist

Hy,

my last posting was some months ago. It took some time to overhaul the complete engine and transmission.

Its a 1971 429cui CJ now stroked to 500cui.
Engine runs good since 400miles, no strange sounds, no blue smoke or something.
Original crankcase, original heads (hand machined inlets, outlets and valveseats) and I also use the original valve covers with the old (but cleaned) pcv valve and oil filler cap.
The oil filler cap looks like a valve cover breather (mushroom with steel whool in it)
After this rebuild I have strong oil mist out of the oil filler cap...allthough there was no oil mist with the same parts before the rebuild.
I have checked the PCV valve, the small holding valve in it is movable and the valve is conected with the air cleaner housing by a hose, but the hose is dust try.
So instead of pushing the oil mist out of the PCV valve to the air cleaner, all the mist comes out of the oil filler cap. Even passangers at the sidewalk are pointing to the engine and the oil mist out of the oil filler cap.

In my opinion, there are 3 possible failures.
1. Oil filler cap is damaged or even the wrong part
2. Pcv Valve damaged or to less underpressure from the air cleaner
3. There should be no oil mist and i have problems with blow by

What do you think? I also have a small video where you can see the oil mist with warm engine.

Thanks!
Stefan from Germany

are the baffels in place in the valve covers?

No baffles under pcv valve and oil filler cap.

They will probably solve your problem

Sounds like someone took them out, the factory valve covers have them.

Good to know, but why do i have oil mist after the rebuild with the same parts?

How does a original oil filler cap look like?
I think there should be a cap that looks similar to the radiator cap which is airtight?

Whith such a oil filler cap, the oil mist has to pass the pcv valve with a little overpressure.

The PCV is supposed to connect to manifold vacuum (usually connects to a port on the base of carburator). You say it is connected to the air cleaner. The oil filler opening (the "mushroom shapped cap") is the air inlet to crankcase. When you pull PCV out of valve cover (with engine running) there should be a strong vacuum on it.

4604X4 wrote:The PCV is supposed to connect to manifold vacuum (usually connects to a port on the base of carburator). You say it is connected to the air cleaner. The oil filler opening (the "mushroom shapped cap") is the air inlet to crankcase. When you pull PCV out of valve cover (with engine running) there should be a strong vacuum on it.

My thoughts exactly. If the PCV is infact in the air filter it's not doing anything. What i've done sometimes is to run the PCV to the manifold , and use a breather with a tube connected up under the air cleaner

The Valve Covers should look like this inside.




I'm guessing the freshen up has got the oil pressure back where it should be or you've added a high volumn pump, Increasing the oil on the top end?

You are right ,I slightly remember that the PVC was connected to the intake same as the brake booster.
Oil pump is a new HV part.
I have to check if there is a connector at the new Demon carb at the base plate.

Just to understand it right:
If I will connect the PVC to the intake and put a breather at the oil filler opening....would´nt this mean a vacuum leak?
Because it would suck right trough the oil filler opening breather???

Sinner motorS wrote:
Just to understand it right:
If I will connect the PVC to the intake and put a breather at the oil filler opening....would´nt this mean a vacuum leak?
Because it would suck right trough the oil filler opening breather???

Yes. The PCV is a "calibrated" vacuum leak.
Fresh air enters the engine trough the oil filter breather and the crankcase blowby is pulled out of engine through the PVC (and drawn into manifold to be mixed with air/fuel and burned).

This means, a new adjustmemt of the carburetor is needed after conecting my pcv valve to the carb. base plate?!

I can not imagine that there will be "enaugh" vacuum for the brake booster after that, but i will try!

Sinner motorS wrote:This means, a new adjustmemt of the carburetor is needed after conecting my pcv valve to the carb. base plate?!

I can not imagine that there will be "enaugh" vacuum for the brake booster after that, but i will try!

Don't forget the 'valve' part of the PCV's name

There will likely be some adjustment to the idle speed/mixture once you connect the PCV properly, but it's to be expected. You need to connect it the way it was intended (to manifold vacuum).

Your brake booster should be connected to the intake manifold behind the carb, and the PCV connected thru the base of the carb. Connecting the PCV to the manifold will mean that one runner is getting any oil mist and that pot may then run differently to the other 7 pots because of the oil mist. Remember that your brake booster is a closed vacuum circuit whereas the PCV is a measured vacuum leak. Your engine will cope in terms of vacuum if plummed properly. If you are running a very large cam you may end up with minimal engine vacuum and this can affect brake performance, but that can be helped with the addition of a vacuum canister.

If you are getting a lot of oil mist then I wonder if you have a problem with rings or valve guides. How did you run in the engine?

@dfi429
The connection of the pcv to the air cleaner was one mistake and it easy to solve.
I´ll try this in the next few days as soon as weather and my time will allow this.

@ianxy351
I can not value the amount of oil mist because i´ve never had this problem before.
Until now I thought the mist out of the oil filler cap breather is just a part of the complete mist, and the other part goes trough the pcv.
But now I know, pcv was out of function, so the mist out of the oil filler cap breather is the oil mist of the complete engine.
After 400 miles the run in is not completed I think.
First trip with new engine was about 300 miles highway (to a hot rod weekender and back).
After rebuild the engine oil was changed after the first 10miles.

As I sayd, i have made a short video of the mist at warm engine. Should I upload it somewhere?

ianxy351 wrote:Your brake booster should be connected to the intake manifold behind the carb, and the PCV connected thru the base of the carb. Connecting the PCV to the manifold will mean that one runner is getting any oil mist and that pot may then run differently to the other 7 pots because of the oil mist. Remember that your brake booster is a closed vacuum circuit whereas the PCV is a measured vacuum leak. Your engine will cope in terms of vacuum if plummed properly. If you are running a very large cam you may end up with minimal engine vacuum and this can affect brake performance, but that can be helped with the addition of a vacuum canister.

If you are getting a lot of oil mist then I wonder if you have a problem with rings or valve guides. How did you run in the engine?

Exactly correct. The PCV goes under the carb at the plenum area. Booster can go to the plenym or intake runner . Run in definitely not complete i wouldn't think. I've found with normal road use the bigger motors struggle to be able to load them up enough without wheelspin and can take a little longer to bed in

What is the right way to run an engine in?
Ride it constantly long distances or to push it right to the 1/8 mile?
...but thats another topic.
This engine puts the whole car to its limits ( frame, axles, driver , ... ) altough there should be much reserves.
The 750cfm Mighty Demon is little bit to small and the heads are restricting the actual setup.

The problem with the mist was a little frightening. If this is solved, the next 500 miles of "run in" can come.

Put the Baffles in the valve covers and hook everything up correctly.

I am running a 466 with 11 to 1 compression and wanted to make sure I did everything to insure I could run 93 octane and not racing fuel. I read that the oil mist that is circulated through the engine at the base of the carb decreases the octane, so I added an air oil separator. This directs the oil mist into a filter and the air that goes into the engine is clean. I drain the glass bowl at the air oil separator after I drive it to remove what it catches. I have mine connected on the intake manifold (#4 cylinder) instead of the base of the carb because my engine produces more vacuum at the carb for my vacuum canister because I run power brakes. The #4 plug looks exactly like the other plugs when I check them. This alone will not solve your problem so you have to do what has been mentioned by the other posts. It's just a suggestion. I got mine at Jegs for $45 .

Definitely get the plumbing correct first and I too like keeping the baffles in the rocker covers, so I would do that too.

In terms of running in, it probably sounds counter-intuitive, but dont baby it. Get a reasonable tune on it in the garage then take it somewhere where you can get some load on the engine. I like the drag strip personally, or a quiet country road. You want to get as much load on the engine as possible for, say, six or more 1/8 - 1/4 mile passes. You dont need to run one after the other - let it cool down and check things are ok between passes - but get some load on it to help the rings bed in. The other option is to find a big hill and from a slow rolling start head up the hill at WOT in top gear - again you are looking for load to bed the rings. The other thing to watch out for is idling the engine too long. This will glaze your bores more than anything else you do. So, ideally, once you have your new engine fired up, set a basic tune and settled any leaks, etc, get it on the road and running in. Dont sit in the shed listening to it idle!

If you sort your plumbing and still have a blow-by problem than you probably have glazed bores. Someone may be able to suggest a treatment for this, but my preferred method of resolving is to buy a full gasket kit, pull the motor down, re-hone the bores and reassemble then run-in again. A hassle but guaranteed to work!

There are some realy helpful answers and ideas. Thank you!!!

@ianxy351
I totaly agree with you. I took the engine to the 1/8 mile after the first 150 miles to not treat it to soft...and check the engine on higher load.
No full throttle but 3/4.


By the way, more and more I think my engine is a ThunderJet instead of CJ.
The valve covers showed some posts before, are aluminum parts.
My covers are deep drawn sheet metal parts with "Ford powered" pressed in.
I have a engine tag but I am not able to decrypt it.

The steel covers have similar baffles.