Moss Motors, Ltd

Greetings all!

 I have a problem with an otherwise (mostly) perfect restoration, and reading in this forum, I see that others have experienced this too but may not have found the cause.  Here are some of my observations.

As a background, my '72 Midget (1275) has had a top to bottom restoration done on all of it and I've been through the engine thoroughly (vatted, bored, turned, balanced, alloy head, etc.) No expense was spared to do the job right.  I did the work myself, except for the machine work, and I am an experienced mechanic.  I should mention that I live in the SE USA and this car is operated on 60F days minimum.  The smog pump was missing when I got it, but the evap system is still intact.

 When starting the vehicle cold, everything is fine.  I back the car out or the drive and accelerate down the road.  The first time you run it up through the gears (within 2 miles or so) it suddenly blows great clouds of oil smoke out the back.  I should mention that it also did this before the major rebuild on the motor.  I traced the problem to the oil separator on the timing cover.  It fills with oil and apparently burps a significant quantity of oil up the breather tube into the carbs.  I have verified this by running the engine at fast idle and observing the inside of the separator.  While observing the oil in the separator, removing the oil fill cap had no immediate effect on the oil level in the separator chamber.  If I were to bring the car to operating temperature before driving it, this would not happen, but very few folks drive like that.  If I disconnect the crank breather and run it, it doesn't blow smoke either.

It is not crankcase pressure as best i can tell, not entirely.  Using a pressure gauge mounted to the evap canister input on the valve cover, I determined that the crankcase pressure reaches about 1/4 - 1/2 PSI before the smoke starts and the pressure drops off (and stays off) for the rest of the run.  My separator is NOT clogged and neither are the oil return holes from the timing cover to the crankcase.  I am running 10W-40 oil. The separator just fills up momentarily and then once it "pops", the system behaves normally.

I used to own a '73 1275 back in the late 70's and it never did this, ever.

I have seen others post here of this exact same problem and they never gotten a definitive answer.  It was always, rings, guides, seals, etc. Thats not the case here since all that is new and I have a smoking gun. (pun intended)

Am I just missing something. 

Has oil changed that much and the separator is no longer "adequate" for todays oils?

 

Thoughts?

Michael

 

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-Michael

Michael,

I am by no means a qualified mechanic (unless the "car" happens to be an R2-R network, OP-AMP, analog to digital converter with hysteresis for a nicely integrated wave shape!) ...I digress...

Are you using ZDDP in that oil? If not, you'd best be. I DO know that ZDDP has been removed from almost all the oils on the market today, and that it is required for the flat tappets in your engine. What I DON'T know is if it affects the operation of the oil separator.

In any case, if you're not using it, you should. At least that will eliminate one variable from your conundrum.

 

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Don't knock it till you've tried it!

Thanks for the heads up.  I guess I need to find an oil that has some, such as diesel truck oil, from what I've read.

Considering that I don't drive this car that much anymore (I work 60 miles away now in a questionable part of Birmingham so commuting is out),  I'm tempted more and more to sell it.  If I only drive it 3 or 4 times a year, its like having a boat ... I have to prep it for the road everytime I want to drive it.

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-Michael

That lower thorax guy (thing?) is spot on with the need to use an oil product with added ZDDP.  Any older engine that doesn't have the current roller-style cam lifters will suffer accelerated cam lobe wear and premature failure using today's current motor oils.  Several of the oil suppliers, like Castrol, have come out with a product (usually 20W50) labeled "For classic cars w/o catalytic converters only".  That product meets the old 1986 SF ZDDP standard (1200 ppm).  All "Red Line" oils have the full ZDDP additive, but old Brit motors are not known for their ability to retain synthetic oils.  A mineral oil-based product is Valvoline VR1 "racing" oil, which has the full ZDDP additive.

That's an odd problem Michael,

 I would have first asked if your separator was blocked, but you mention that is not an issue. If this part is clean, free breathing and can allow the oil it captures to run back into the engine, then it's hard to find fault there. Hmmm...

I'm not at all familiar with the setup on the Midget, but is there a PCV valve or other arrangement to regulate flow from the breather, and is this in good condition? I miss assembled the PCV on my MGB on one occasion, and it immediately began to suck oil out of the engine like there was no tomorrow, prodicing clouds of white oily smoke!

The car works beautifully now with Shell 20W50, plus the ZDDP additive that Mr Liver wisely suggests, I don't think there's anything connected with oil that is causing your problem.

You could put a catch-pot on the end of the breather and see just how much oil it is producing each time you run the car. Depending how sophisticated you want to make this arrangement, either plug the other end of the breather line, or use/devise a catch-pot that can be plumbed into the system.

Sorry I can't think of anything else, but best of luck,

 Cheers

Ed

 

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I want my MGB

the late 1275s do not use a PCV valve, but when they did, the breather setup was the same.

The vapors enter the carb bodies roughly between the butterfly and the slide.  The vacuum produced can barely be felt, but is probably a little higher at WOT.  There is no valve at all.  Leaving the line disconnected, or leaving the oil fill cap off (accidentally drove 60 miles on the highway like that once) produces a rough idle and no other running issues. 

I personally feel like a larger separator would fix this, but it puzzles me as to why it does this.

I first put this car on the road in 96.  It smoked just like this then, but I had not done a complete overhaul of the engine, just honed it and replaced  the rings since the old girl ran when I pulled her down, I assumed she'd run a little longer.  Back in 03 I pulled it down again and did the whole thing as new, since I was tired of the piston slap.  I put in a Rivergate 5 - speed conversion kit at the time as well,

I did some experiments a few years ago, placing some copper wool (scouring pad) inside the breather line.  This seemed to work, but when you let the car sit for extended periods (months) it smokes immediatly on startup.  Inspection revealed very bad condensation accumulation inside the breather line which I assume was percolating oil into the carb bodies.  If I drove it evry day as it was intended, I don't think that that would be an issue.

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-Michael

Thanks for the clarification of the system. My MGB breather connects to the inlet manifold - that's why there's a PCV in the line, otherwise there would be full manifold vacuum on the crank case...

I wonder if your problem could be eased by improving oil drainage from the separator i.e. more or bigger holes. It would seem that if so oil is collecting here to the extent it's carried over to the carbs it needs a better escape route. Or put a catch-pot in the line - but you'd need to empty this once in a while...

Ed

Edit: one other very remote possibility occurs to me - could you have the wrong, or an incorrectly marked dipstick, and as a consequence, too much oil in the sump?

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I want my MGB

The oil separator is a cylinder about 2" in diameter and about 5-6" long. it has a spigot, about an inch in diameter on one side down low that enters the timing cover.  Inside the upper half of this is a mass of metal wool, suspended between some kind of wire clips.  The only hole is that spigot, there is no sheet of metal with holes like you might find in a valve cover on a modern car. 

The car has the correct dipstick (I have 2).  The oil level is correct.  BTW, it will do it when the oil is low too.

I can stop the excess smoke by installing about 6" of copper wool (scouring pad) in the breather line from the separator to the carbs.  I know from the past that it stops the symptom described here, but causes another one when it sits for months, namely condensation occurs in the line and percolates oil into the carbs resulting in a cloud of smoke you wouldn't believe, immediatly on startup.  I'm going to try leaving the evap system loose to see if that reduces/eliminates this condensation.

 

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-Michael

Hi Michael,

I found a diagram showing the separator in the Moss online catalogue, so now I know what you are referring to. As for explanations for the strange behaviour of the breather system, I think I've run out of ideas.

You say that if the engine is allowed to warm up before driving, the smoke is not produced, is that correct? This is odd, as one might surmise the oil is always there at startup ready to "burp over" - as you put it.

Sorry I can't think of anything else,

Cheers,

Ed

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I want my MGB

I know this is an old posting but I have recently been battling the exact same problem and I too believe the problem is coming from the oil separator.  I just don't know what to do about it absent looking for a "new" timing cover/separator or changing the carbs to versions which do not take a suction on the crankcase.  I will try introducing additional coarse "steel wool" or "greenie" material into the hose from the breather to the "Y" fitting at the carbs. I believe the problem is so bad now that I am fouling plugs.  I took the head off last night and oil was literally pooled on the top of the pistons...Any other ideas?

Sounds like something is clogged up with an oil/water emulsion.

 I have to clean my crankcase ventillation components every so often. Excessive crankcase pressure can cause what you describe.

Help! Please restart this thread. My 73 also has pooled oil on the 2 middle pistons. As I read this thread, I didnt see a real answer on how to fix the problem. Can or should a PCV valve be installed in the line between the oil seperator and the carbs? Anyone have an idea on how to fix this problem? Should I "flush" out the oil seperator with carb cleaner, flushing back into the oil pan? This setup must have worked, but now something has changed to cause this problem. My cylinders look great, no scoring or scuffing. Very little piston play in the cylinders. I have only 65,000 miles on the car. Serial # GAN5UD135**G if that helps. All of the catalogs seem vague on the need for a PVC valve for my year car. I dont want to install my engine back in until I can figure this out. Thanks for any help you can give me.    Kayakdon

Hi.first thing I would do is get rid of 10/40 oil and replace with 20/50 Oil additive not necessary unless you were driving through death valley california. If you got a worn engine then maybe wynns or stp oil additive will quieten it down,otherwise,20/50 should be fine. If it still smokes,make a special trip into an approved dealer and let them have a look,before this problem spoils your driving pleasure any more. Phil.

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phil wilkins

I agree with Phil on 20/50 grade. Also Im not sure that your problem is necessarily the same one as this thread. I think that if you have poor rocker cover gasket and or oil filler cap you will be pulling too much  air via these leaks into the crank case and picking lots of oil when hot  and at revs. [There should only be a slight air inlet into the system via the  needle hole in the pipe stub on the top of the rocker cover.] If this were the case I would not be surprised at the build up of oil that you describe, Ive been there and I was using 20/50 grade! I would recommend you try the approach I outlined in the other thread on oil-consumption, currently running. Hope this helps,   Cheers    - - - -  steve

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To a man equipped with only a hammer, most problems look like nails

Hi Again, As stated in this thread, my car only smokes on start up. It will smoke real bad for about 2 minutes, then it is fine. The oil is coming up the hose from the oil seperator to the carbs. My valve cover isnt leaking,  my cap is sealed, and the pipe stub has just a very small hole in it. All original, no mods to mess up the original set up. There has to be something that has changed over time to cause this problem. Sucking oil through the oil seperator is not normal. Anything from worn piston rings, worn seals,poorly adjusted carb,  to clogged air filter. Maybe the air pump that pumps air into the head is pumping too much? I was hopeing that someone had an answer to the original thread that was answered via private email and not listed here. I sure hate to put the engine back in only to find out that I need to replace something that I need to pull the engine  to do.   Thanks, Kayakdon