Bugeye smoking from the breather tube

[TulsaFred]

Been doing body work, but decided the car needed to be run a little, so I took it around the parking lot a few times.

When I got back I noticed it there was smoke sort of puffing out of the valve cover breather tube and around the oil filler cap. Kind of a neutral color,not black or blue, kind of grayish. Fairly small amount but definitely noticeable.

I never noticed this before.

Since my dash and gauges and wiring are all ripped out now, I couldn't check oil pressure or temp, but the car seemed to be running just fine.

?Blowby
Why now?

Fred

 

[BlueMax]

Fred,
If you would like to determine if you have BLOW BY here’s a very simple way. Plug the little breather pipe on valve cover with some duct tape. Then take a latex glove placing it over the oil fill hole on valve cover. Secure the glove in place with rubber bands. Crank the engine up giving it a few rev's around 3500 rpm's. If the glove blows up like a balloon then you have BLOW BY, simple as that!!

 

[Rut]

Fred,
Has the car been sitting for awhile? You may just have some condensation that was 'burning' off. If you have the oil separator connected to the manifold and the breather from the valve cover t'ed in or connected to the carbs, you may have enough negative pressure to keep the glove from blowing up. I just put a piece of plastic wrap over the oil filler opening and watch to see if in sucks in or blows out. If it blows out, I'll do the glove test.
Rut

 

[TulsaFred]

Thanks guys,

If I do have blow by, is it always the rings? Can bad valves cause the blow by?

It's odd that it hasn't done this over the past year or so, and now it appears.

When I bought the car, the seller (an intermediary actually) told me that 3 of the 4 cylinders had good compression, but one showed a problem. I assumed the engine would need a rebuild anyway and didn't think much of it. I was then pleasantly surprised at how well the car ran once I got it started. It didn't smoke or make bad sounds, basically seemed fine. Still does, starts right up as soon as you hit it and doesn't miss a beat.

So today with the new issue I pulled out the compression gauge and tested the engine.
Cylinder 1 : 145 psi
Cylinder 2: 150 psi
Cylinder 3: 145 psi
Cylinder 4: 100psi

So it's basically as the seller stated. Cylinder 4 has low compression. I'll do a leak down tomorrow to investigate further. Perhaps #4 has a ring/cylinder problem. Still, if its been this way for a year or more and hardly been driven, why would it start causing blow my now?

I think the p.o. rebuilt the engine some time ago. It hasn't seen any significant miles since he never finished the car. It has been a project for many years and I bought it and hope to finish what the p.o. started.

Maybe the rings didn't seat on cylinder 4.

I'll try the glove test tomorrow along with a leak down.

Fred

 

[Deleted member 8987]

If it's puffing, it's probably a couple of broken rings on one cylinder. Puffin out the breather indicates that. Wait until you see one do smoke rings.
Head, sump, knock the pistons out.
Valves are NOT going to give you blow by.

 

[Hap Waldrop]

To answer your question about excessive crankcase gases, they are always of result of rings, not valves. Let me run this by you, you say you're getting a good bit of blow-by at the valve cover, where else is the engine vented, a 1275 should at the timing cover, 948/1098 at the lifter cover. Theres very little access for the A series engine to vent from the head alone, so thats whay I'm asking you if it is vented somewhere else besides the valve cover. Yeah #4 compression don't look great, but venting from another place beside the head is mandatory on these engines.

 

[TulsaFred]

Hap,

This is the 948 stock engine that is in the car (my 1275 is on an engine stand getting my slo-mo rebuild).

As far as venting, I only know of what I am referring to as the "breather tube". The 90 degree bent tube coming out of the top of the valve cover (gasses also seem to be venting around the oil filler cap as well). This tube is open to the air and doesn't have any type of hose on it. I'm not sure if it is supposed to or not.

Does this answer your question?

Thanks for the help!

Fred

 

[TulsaFred]

Here's the result of my leak down test. I've never done one before.

I didn't want to take of the valve cover, so I compared number one cylinder (good compression 145 psi) to number 4 cylinder (bad compression, 100 psi).

My logic is that number 1 TDC can be found by lining up the timing mark on the crank pulley. It could be exhaust or compression, so I checked leakage to confirm number 1 was at TDC compression.

Doing this gives me a compression loss of 28% average over 3 measurements. My gauge says this is "low" which is good. Comports with the good compression reading.

Next I located number 4 TDC compression by again lining the timing mark up, only this time confirmed by leakage that it was exhaust of number 1, which should be compression of number 4 (if you follow).

Doing this gives me a compression loss of 45% average over 3 measurements. My gauge says this is "moderate". Obviously, again confirms an issue with number 4.

Now the odd thing is, air is clearly leaking out of the spark plug hole of number 2 cylinder when number 4 is being lead tested.

My gauge manual says to listen for leakage at Oil dipstick hole (indicates bad rings or ring-cylinder seal), air horn (indicates burned intake valve), tail pipe (indicates burned exhaust valve), radiator cap (indicates cracked block or blown head gasket), or ADJACENT cylinder (indicates blown head gasket).

It says nothing about a non-adjacent cylinder, as I have.

So there is a riddle for a smart motor head. I'm sure there is a very logical explanation. My initial newbie thoughts, in order of likelihood:

1. I did the test wrong (since I've never done it before and kinda came up with my own technique for finding compression TDCs).

2. Odd head gasket leak connecting 2 and 4 (seems a stretch).

3. Something connected with the valves. In other words, when 4 as at TDC compression , 2 must be opening an intake or exhaust valve and the air is getting in via the valve. ? odd crack in block or head connecting combustion chamber of 4 to intake or exhaust passage of 2? (seems a stretch)

Something else?

Fred

Also, since this problem with number 4 cylinder has been known for a long time and the possible blow by is new, they may not be connected.

 

[HealeyRick]

Fred,
If you would like to determine if you have BLOW BY here’s a very simple way. Plug the little breather pipe on valve cover with some duct tape. Then take a latex glove placing it over the oil fill hole on valve cover. Secure the glove in place with rubber bands. Crank the engine up giving it a few rev's around 3500 rpm's. If the glove blows up like a balloon then you have BLOW BY, simple as that!!

Generally known as the "Mandel Method" of blow-by testing:

 

[regularman]

You are always going to have some blow-by. There is always a certain amount of air that leaks by the rings. It sounds like you don't have positive crankcase ventilation going on. There should be vacuum there pulling that blow-by away. You should have a hose coming from the intake at some point going to a couple different places to make this a vacuum. Also its the number one reason why people have major leaks at the scroll seals, because there is pressure in there blowing the oil out instead of a vacuum on the crankcase.

 

[Deleted member 8987]

When he says it's puffing (not drifting), and gives compression readings, not much a PCV will do.
"When I got back I noticed it there was smoke sort of puffing out of the valve cover breather tube and around the oil filler cap."

Puffing out the breather tube AND cap with low compression on one hole......needs to have the pistons out, or good towing insurance.

 

[aeronca65t]

.......I think the p.o. rebuilt the engine some time ago. It hasn't seen any significant miles since he never finished the car. It has been a project for many years and I bought it and hope to finish what the p.o. started.

Maybe the rings didn't seat on cylinder 4.....

Fred

Yes. Rings may not be fully seated or even stuck if sitting for a long time. Maybe just running it a bit will help.

I'd be tempted to pour a bit of kerosene down the #4 cylinder, let it sit for a while and then give it a good run (and then re-test compression.leak down).

Also, you may have a sticky valve. Pretty common in these engines if they sit for a long time. This won't cause blow-by but it can cause low compression and poor leak down results.

 

[Deleted member 8987]

Maybe. Probably not. Seen a whole lot of "puffers" in my day, every time we were able to dig into one, broken rings or piston. Bon-Ami? I had a shipmate in the Navy who rebuilt big MoPars, he'd take them out on the road to 80 in second, shut them down with the pedal to the floor until is slowed, restart, do it again.....gas washed the cylinders and seated the rings. Not sure if I'd want to try that.

That low cylinder....rebuilt, eh?
I remember some "rebuilds" as a new valve cover gasket and a repainted valve cover.
If it has out-of-round cylinders, and the "rebuild" consisted of new rings, well, be a long, long time until it "breaks in".

Smoke is one thing, "puffing" indicates something else, usually.