Driving to Hershey, after about 2 Hrs of driving, going up a ramp, I notice white smoke coning out of my tailpipe, pulled over and noticed that there was oil on the air cleaner unit. got in the car, drive to get off the freeway, the smoke was gone. I stopped cleaned the air cleaner unit and noticed that the oil was coming from the flash back valve.
the car never lost power or stumbles.

Drove it an other 100 miles, no issues.



1974 Djet

See post 8

Paul, not familiar with flashback valve??? EGR or Decel Valve?

Same thing happened to me. P.V.C. valve. Cleaned it and no more problem...???

The little thing with three ports for hoses on it that sits under the left side of the cross-shaft for the cooling flaps. It has a screen in it, to keep any backfire flames from propagating into the crankcase.

--DD

There is no screen on mine. It looks like a simple T

Is this on the carbed car ?

No, the djet.

Here is the update. I drove the car home today and the same thing happened as I was going up a hill.
Here is what I did prior:
I changed the oil, the filter and filled it up using 3-3/4 qts. I did not remove the sump.

Behavior: the oil comes out of the passé he's wide air vent, up to the flashback valve then to the air cleaner, make its way to the throttle body that caused the smoke.

The car runs fine other than the smoke. Usually last a few seconds.
I also noticed that the vacuum line coming out of the breather to the plenum flattens out when the car is running. Looks like it's sucking air instead blowing, causing it to flatten.
When I checked the oil at the first occurrence, after shutting down the engine for 2 minutes. the level was between the two lines.

I added about half a quart before hitting the road this morning since it was under the first line. When I pulled up after the second occurrence, it was way over the top line.

Help!

I was the guy in the black cap today at Hershey, if we happened to meet up today.

Just off the top of my head, if you're seeing smoke uphill, you might be having a valve cover leak towards the back of the motor due to the inclination. Oil will leak onto the heat exchangers and you'll be guaranteed to have some smoke. I have a bit of smoke on the drivers-side when going downhill, for instance. *rolling window down*

That said, oil up by the air cleaner is something else. I'm no expert, but I've had stuck vents off of a valve cover (some have them / some don't, depending on the motor), a reason to clean the PCV valve or look at the primary or secondary oil relief valves. Just a few ideas.

Scott,

Look at this
Joe had the same issue
Not looking good

" how the hell did that TDC quote got inserted into my post?

Thanks,
I will check compression today, That will give me a better idea.

oil coming out on one side only is what's got me thinking that it's not overfill.

Will post results shortly . Looking for instructions on leak down test. Any links?

GEt the cyliner you are testing to TDC so both valves are closed.
Look at the valves, make sure they are closed.

Fill up the cylinder with air.
Listen (use a piece of hose like a stethascope)

Listen down the oil filler for air...that would be rings.
Listen down the carb of that cylinder for air...that would be intake leaks at the valve.
Listen on the outside of the exhaust pipe right at the head...
That would be leaks at the exhaust valve.

The last one is the hardest to hear, but in a calm room you can hear the leak.

Most likely you may need rings.
The back pressure blows oil into the head...and with high rpm's on the highway, it blows that oil into the head venting system.
WIth bad rings is pressurizes the case behind the piston so the head venting system does not work right anymore.
Oil wont drain back into the case, now it gets sucked into the intake.

Its a path of least resistance type design...
ITs supposed to go from vapor back to liquid and slowly drain into the case again.
High pressure in the case makes is blow backwards.
That is bad rings....and I have only seen it on highway runs over a long period of time.

It seems hard to replicate on short drives.
The system has enough leaks (valve guides, valves, etc...) that it does not show up till you take it on the highway for a while.

Heavy load (going up hill on the highway) makes bad rings show up more.
There is more side load on the piston, combined with higher rpms, and you get alot of pressure going past the rings.


I put an external venting system in place from CB performance...
It worked for a while, but at the end of the day, you need rings.

For a typical ring job, it can be done in a weekend (if you stay focused and dont look at anything else "while you are in there")
It is a DIY job with simple tools you can buy at the local NAPA store.
YOu need to hone the cylinders.

You will need a cylinder hone for your drill.
You need a ring compressor tool
You need a torque wrench.

The rest is removal , lots of cleaning, and re-install.

Honestly, most of these high mileage motors need rings.


Rich

Compression is at 160 on all four cylinders. Tested with throttle fully open at operating temp.
Does that change your diagnostic Rich?
Is a leak down necessary with those numbers? All spark plugs are dry and clean

compression and leak down are two different things.

You need to determine why your PCV system is pressurized....

Does not change things for me...you still have a problem.

Ring "blow by" does not really show up well on five or six turns doing a compression test.
It shows up over a longer period of time.

You dont need fancy guages or a special leakdown tester.
Take the hose from your compression tester and put a fitting on the end to hook up to your compressor.
100 PSI over a long period tends to simulate it enough to hear the leak.

These motors do leak...its just a matter of how much, and from where.
What you are looking for is an anomoly.
Your compression test demonstrates that there are no major differences between cylinders.
So, now do a leak down for further diagnostics.

Compression test are good, but only show so much data.
Next up, leak down...



rich

I know for fact that my pcv valve is not functional. Could this be the cause?

still pressurising the case.
Look deeper.

rich

Listen down the carb of that cylinder for air...that would be intake leaks at the valve.

I have fuel injection, can you clarify the underlined


Listen on the outside of the exhaust pipe right at the head...

not Sure about exhaust pipe at the head, do I need to remove the heat exchangers?
That would be leaks at the exhaust valve.

Leak down test shows leak on all cylinders with 100 lbs of at TDC on each cylinders. The air is leaking thru the oil filler neck. I hope I did it right.

All engines leak.
When the rings are push up, the expand and seal off the cylinder, the back drag down and settle a bit looser.

The leak down test is for determining where to go next.

If you put the hose to your ear, and put it right on the tube that goes into the head at the intake port or the exhaust port, you can hear a pretty large difference that would show you if you have a burnt valve or dropped seat.

Your problem is just an old engine.

Rings get very dirty and need to be replaced.
How many miles are on your motor?
Re-ringing this engine is not a big bad problem, it just takes time.

You will end up cleaning off years of crud on the cylinders, under the tin, replacing all the pushrods tube seals and end up with a cooler running motor that had less blow back.

If you are getting a lot of oil blown into the intake when you are at high rpm,s you may need to replace the rings.


Have you been able to reproduce the problem?
Try this.
Block off both head vent tubes at the head with a rubber hose, two clamps and a bolt in one end of the hose.
Car won't blow up...

This will show you that your venting system is part of the problem.

Like I said before, you can put on an aftermarket oil breather, but at the end of the day, the fix is to deal with the rings, and valve guides to tighten up the pressure again.


Rich

I cleaned all the thins oil cooler and all external components for a good air flow a few months ago.

I don't have a history on the engine as far as mileage.
I do not experience the issue during high revving, just this time after driving about 100 plus miles.

My question are:
The leak down results is pretty much th same on all cylinders, why is it leaking only on one side.
If I block the pcv port from the filler me k completely, can that cause this issue?

The case needs to breath or it will either crack, or all that pressure will find a new way out...so don't block that port.

Rich

I will not, The only reason I asked is because that port was pretty much blocked.
The vacuum line that I was using from the breather to the intake was not able to sustain the heat and was sucked in.

I guest, that will be my winter project.

Thanks for all your help

Could be a big part of your problem.

Compression test sounds good....remarkable actually.
Leak down sounds like all are the same.
PVC line or port is blocked.

I would fix that now....then go find a hill and make it do it again.

Rich

I guest I have to plan my next trip to boston to see my dad.