(Minor) Blow-By and Crankcase Ventilation Questions

[LandShark]

1965 110/PG – stock set up
Hi All,
So I am experiencing some white smoke from the crankcase vent tube into the air cleaner that I believe to be some excess crankcase gasses caused by what I guess is some blow-by. I'd say it’s fairly minor as there’s no oil pooling in the air cleaner, nor do I have any spraying out of other areas like the dipstick. When I cap the vent tube with the oil cap resting, not tightened, the oil cap does dance some.
It is only really a problem after driving for a while.
It causes the car to want to stall at stops (in drive) – I say it causes it because when the cover of the air cleaner is removed, the idle goes right back to where it needs to be and it runs as it should. The smoke seems to be messing with the air through the carbs. The car doesn’t smoke through the exhaust and I don’t think it burns much oil (I haven’t really put enough miles on the car to know for sure).

Some of what I’ve done so far:
I have thoroughly checked and cleaned out the crankcase vent tube (including orifice) and balance tube. It is how it should be, clear and set up properly.
I did a solid tune-up including balancing and adjusting carbs.
I did a “flush” (one of those engine flush cleaners that you add, run the engine for 5 minutes and change the oil).
Switched to thicker oil (from 10w30 to 10w40)

I had it out the other day for a nice long drive and the problem seems to have lessened a bit but is still present.

Possible plan:
1. Enlarging the fixed orifice slightly. I understand it’s supposed to be .0625, maybe go to .068 or .089
2. Adding “Engine Restore” additive
3. Modification of crankcase vent system --- individual air cleaners and little air filter on vent tube (I know, most of you are not fans of this –heck, it’s a convertible, I don’t use the heat anyway!) --- or convert to vent under the engine (I know….pollution).

My father always taught me to look for the simplest solution first and if I can avoid (at least for now) doing a ring job, I’d like to. I am pretty good at fixing things, and not a rookie when it comes to working on cars but I am still pretty new to Corvairs.

Have I missed anything?
Any other things I should consider trying?
Different types of ventilation mods maybe?
Anyone have any thoughts?

Thanks in advance,
Chris

[b74eqcm]

Simplest solution first? I'd do a compression check and see what the numbers are. If compression is good, then I would try your options - although none of those should be necessary.

[66vairguy]

As already stated - DO A COMPRESSION CHECK!

I think you are looking for trouble were there is none. It' very common for some vapor to come out of the crankcase on startup. Even new engines have a little ring blow by. When an engine is cold the combustion gases produce moisture (why you should always run an engine long enough to heat up the oil before shutting it off) that looks like white smoke.

Do check the orifice and tube to make sure they are not blocked (very common on older engines or ones where the oil was not changed often enough). DO NO CHANGE THE ORIFICE SIZE - it is a calibrated opening and opening it up will lead to poor idle problems.

Even with the orifice open some fumes can/will go to the air cleaner depending on engine load and vacuum.

DO NOT block off the tube to the air cleaner. It is needed to let in air to keep the orifice side at normal air pressure otherwise the air bleed through the orifice to the carburetors will not stay constant and you will get a poor idle.

[Vin]

I experienced exactly what you describe on my 65 Monza. It had been running well then didn't want to stay running at idle so I would have to review it at stop lights. Took air cleaner off and it ran fine. Then I saw the large blow by out the vent tube and concluded with the air cleaner on the blow by was sacking into to carbs causing the problem. As stated above you now need to do a compression check. When I did I found low compression on #5. Put a little oil down the Spark plug hole and rechecked and compression went up some but then after a wait it went back down which indicated broken rings. Lowered the engine and found broken rings on #5. Hopefully you will have better luck.

[LandShark]

Hi Guys and thank you for the replies,
I'll get on the compression check next. Problem is minor at this point, more of a annoyance, so no urgency, I would just like the car to run a bit better than it currently does. I hope "66" is right and I'm just looking for trouble where there really isnt any. Even still, if I end up going down your road Vin, I hope it's not for a while or my next post may be "How do I change the piston rings on my 110?" I'll get to the compression test eventually, and when I do, i'll post the results.
Thanks again
Chris

[bbodie52]

...I hope it's not for a while or my next post may be "How do I change the piston rings on my 110?"...

Start by downloading and reading the appropriate section of the factory shop manual. That was my "bible" in 1969 when I overhauled my first Corvair engine and automatic transmission at the age of 16. That shop manual led me every step of the way. In 1969 there was no Corvair Forum, no Internet, no CORSA clubs, no Clark's Corvair Parts, etc. I was on my own with a garage, jack stands, a floor jack, hand tools (all complements of my father, who was not present to guide me during my summer vacation from high school, as Lockheed had transferred him to a location hundreds of miles away).

I would highly recommend that you read the shop manual, and then turn to the Corvair Forum and/or a local CORSA club chapter, if one is available, for further guidance, if needed.

The entire manual and many other Corvair technical references can be downloaded at no cost using the following link...

Common and Useful Corvair Websites
viewtopic.php?f=225&t=6007

[LandShark]

Thanks Brad
I'm definitely going to give it a read through ...just in case.

[LandShark]

UPDATE:
Okay so, finally (a year later) got around to the compression check. Been just driving the car and enjoying it and dealing with the above stated issue, which, as I mentioned, was basically an annoyance.

Numbers don't lie!
#5 piston is at about 50 psi while the rest are all in the 150-170 range.
Added a bit of oil to the cylinder and tested again to get about 65 psi.

At this point I'm going to approach it as "stuck" rings rather than broken rings and see what I can get to happen. if all else fails, looks like I'll be in for some real fun.

[Jerry Whitt]

Low compression is possible with several possibilities.
1. Poor ring
2. Valve leaking
3. Head gasket.
4. Cracked head or cylinder

A leak down test would help narrow the items. Air pressure is put into the spark plug hole with the piston near top dead center. A leak down gauge is used (many auto parts stores will loan the tool). Theory, air pressure will leak out and noise will be produced.

1. a If the ring is bad, the gauge will show a high number, above 20 %. There will be a noise from the oil filler tube.

2. a If a valve is leaking, you will here a noise at the carburetor, or the exhaust pipe.

3.a If no noise apparent at 1a or 2a, tear down is next.

Good luck

[LandShark]

Low compression is possible with several possibilities.
1. Poor ring
2. Valve leaking
3. Head gasket.
4. Cracked head or cylinder

A leak down test would help narrow the items. Air pressure is put into the spark plug hole with the piston near top dead center. A leak down gauge is used (many auto parts stores will loan the tool). Theory, air pressure will leak out and noise will be produced.

1. a If the ring is bad, the gauge will show a high number, above 20 %. There will be a noise from the oil filler tube.

2. a If a valve is leaking, you will here a noise at the carburetor, or the exhaust pipe.

3.a If no noise apparent at 1a or 2a, tear down is next.

Good luck

Hi Jerry,
Thank you for the reply and information. I did a "sort of" leak down test in which I used my compressor and l supplied air to the cylinder (no guages) and listened. Strangely, I heard air from both the carburetor AND the the oil filler tube and not the exhaust which doesn't make sense to me. I'm probably going to try again thinking maybe I wasn't truly at TDC.

Sent from my SM-G930V using Corvair Forum mobile app

[bbodie52]

...Strangely, I heard air from both the carburetor AND the the oil filler tube and not the exhaust...

With both the intake and exhaust valves fully closed in the cylinder under test…

Sound of air leakage heard through the carburetor equals a leaky intake valve.

Sound of air leakage heard through the oil filler tube equals blow-by past the piston and piston rings.

Sound of air leakage heard to the exhaust equals a leaky exhaust valve.

If you suspect a leaky intake valve you would want to check to verify that the valve adjustment is not excessively tight on that rocker arm, which could cause some leakage if it is too tight and the valve is never fully closed. Of course running the engine in this condition can eventually cause a burned valve or valve seat as hot gases leak past the valve.

There will always be some blow-by past the piston rings and pistons. A perfect seal is not expected, but using an air gauge to measure the percentage of leakage helps to determine if excessive wear of the rings and/or cylinder is an issue. But if you hear leakage also through the intake valve you have leakage in both locations and it would be impossible to measure the percentage that can be attributed to the piston and rings versus the percentage that can be attributed to the intake valve. The same would be true with a compression test that is low in the cylinder. The low number may be attributable to a leaky intake valve and a normal seal from the piston and rings, or you may have two problems in the same cylinder caused by a leaky valve AND a worn cylinder and/or piston rings.

[LandShark]

Thank you Brad. Guess my plan is the adjust valves and go from there.

Sent from my SM-G930V using Corvair Forum mobile app

[LandShark]

Okay, hot valve adjustment finished.

I did have one valve that when I tightened it would stop tapping then slowly begin to tap again. If I tightened more, it would start to miss so I was able to realize when it was too tight. I've had problems with the tapping on that cylinder in the past but it was mainly after a long time sitting (couple of weeks or so) and would usually go away after the car warmed up a bit. Could it be a bad lifter? or a lifter that's on its way out?

Test drive showed no real improvement. Still lots of excess crankcase gasses. Car runs better when I open the oil filler cap.
I think I'll check the compression again, do the air test again, and probably treat for a stuck ring and see if that helps. If not, I can always rig it so the excess crankcase gasses vent out of the engine compartment sort of like a road draft tube and just run like that until I can pull and refresh the head/ fix the rings or start prepping my spare motor.