Crankcase ventillation

[Sony2000]

The older blocks have a trap door by the power takeoff, to use for adding oil. The cover is designed not to close exactly over the rectangular opening, but beyond the opening, allowing air into the crankcase preventing changes in pressure.
With older engines there is smoke escaping. The newer blocks have another arrangement.
So could I cover better the opening, and prevent the smoke from freely rising?
A little square of tin attached to the underside of the trap door would help a lot.
Smoke rising from the crankcase could still leave over the flame arrester, or push open the trap door when it could.

[romantic comedy]

Worn engines experience blow by from combustion. This makes pressure in the crankcase that needs to vent. I dont know how much volume of smoke and air will come out, but it will come out one way or another.

I dont think the location of the vent makes much difference. Many guy use a PCV valve to help ventilate the crankcase and remove the smoke. I recall a couple threads on this issue.

Dont block off the air escape without opening another route. There is pressure that will be relived one way or another.

A rebuilt engine would not have the smoke problem. Aside from getting a rebuild, the pcv valve has worked for many.

[ILikeRust]

The Atomic 4 crankcase is not airtight, so there's not a whole lot of possibility of pressure building up to worry about.

The forward end of the crankshaft (behind the flywheel) is not sealed - there is no "oil seal," as there is on a car engine. If you were to tip the engine forward far enough, you would find that the oil in the pan will run freely right out the front of the engine. Feel free to ask me how I know this.

So even if you were to seal up that little trap door completely air tight, you would find smoke wafting out that front seal - and out the little crankcase vent on the side valve cover.

If you have that much smoke coming out of your crankcase, that suggests worn rings/cylinder walls or perhaps worn valve guides, allowing excessive blow-by.

As Neil will argue, applying a PCV valve to an engine in that condition serves only to mask the underlying problem - at a certain point, it means the engine is due for an overhaul. Truly excessive blow-by will dilute and contaminate the engine oil, leading to premature and excessive wear on parts, making the situation worse, in a downward death spiral... Some blow-by on an old engine is not the end of the world - you just need to change the oil regularly and keep an eye on the condition of the oil - and deal with a smoky engine compartment, or add a PCV valve to help reduce the smoke.

[ndutton]

Sony,

Try retarding the timing slightly and see if it helps.

[Sony2000]

This is my first Atomic and it arrived in a few pieces. Presently functioning well on it's test bed, I want to redirect the blow by, to the carb for reuse. All summer the engine will receive decarbonization treatments, in an effort to increase compression by 20 psi.
It's good to know the odour of crankcase fumes may exit by the flywheel, but at least I won"t see the trails of white smoke from the TO.
I must scrounge up a dwell meter soon. This engine runs with almost any timing setting.

[thatch]

A Critical Componant

Sony,
An extremely important piece of equipment in controlling engine blowby is what we refer to as the vent/slash tube. A good view of what it should look like can be seen on the carburator side of the Moyer site picture. Before adding any other vent system equipment, it is always a good idea to get the ignition set at it's factory spec. and to make sure that the V/S tube is installed correctly. Many of us with "high mileage" A4's are able to keep our engine compartments "smoke free" without the addition of other vent aids.
Tom

[ILikeRust]

Hey Neil, Tom is singin' your song!

[sastanley]

thatch, this weekend I was up at Ajax's boat and we were checking the engine...of course I ran it at WOT at the dock to see how it sounds.

His blow-by is coming out of the oil filler cap & his slash tube was in place I think. I have pointed him to this thread, so he can comment. I also know that he's been fiddling with the engine timing recently, so the 'timing' of this thread is very 'timely' for him as well.

[thatch]

Shawn,
I can almost hear Neil groaning from here.
One other thing that I neglected to mention in regards to the slash tube's efficiency is the condition of the flame arrestor element. Similar to what happens to a PCV valve, these elements do get dirty over time and need periodic cleaning. Because of their "waffle" construction they may look relatively clean but may actually be quite plugged up inside. Soaking in carb cleaner is the method I use for cleaning mine. Ignition timing is a subject that has created much controversy. Because Universal did such a poor job of giving us "useable" marks to go by, the generally accepted method is to "time it by ear". While this will normally give us the most power output, it will also put the timing several degrees ahead of what the factory spec is.
With this advanced timing will most assuredly come increased blowby. Sorry to open up this line of dialog again, but I seriously doubt that it will ever go away.
Tom

[ndutton]

Hey Neil, Tom is singin' your song!

His check is in the mail!

[sastanley]

thatch, your comments are exactly why I am sending Ajax to this thread. He noticed that his distributor was not clamped and he thought the engine timing had slid to be extremely retarded, and it was running bad, and asked me to come visit the boat when convenient (not necessarily in that order, details below.) Before I got there, he figured out the issue and 'power timed' the engine, as is common practice among the A-4 crowd.. When I visited the boat this weekend, it sounded fine to me, but has blow-by coming out the oil fill.

I do also recall that I also soaked my flame arrestor in a 1 gal paint bucket sized can of carb cleaner (Chem-Dip)...generally available from your local auto parts warehouse..that can has been golden for clearing up old A-4 gunk for just about anything that will fit in a 1-gal paint bucket..I am probably having as much stuff settling in the can as is evaporating off the top with the lid open.

Me & Ajax & my other buddy Robert (good friend, but owns a dinghy with no motor) that met up this weekend for St. Patrick's Day festivities only had about an hour to screw off on Ajax's boat...so a lot still remains to be discussed as he discloses his findings. He is like me (probably more so) at wanting to understand things and make them right, within reason.

[Dave Neptune]

Your call

Sony, as per Tom's comments timing and ring -cylinder sealing are common causes of elivated smoke or fumes. Making sure your slash-tube is in good working order will probably help. As far as sealing the opening~no biggie. Confining your fumes to gather and extract is a good thing and the engine can still breath through the front of the crank.
Run a bit of top oil, 2 stroke or MMO in the fuel for a few gallons at least and check the compression again. Probably the single most important thing is to be sure she is in good tune before making unnessarry assumptions. Example, my engine now has better compression than when I got it running after I purchased it and that was 26 years ago. Don't rush these engines show an amazing ability to "heal" with good care.

Dave Neptune

[Sony2000]

If members are power tuning the Atomic they maybe overlooking an important element, octane. Adding MMO not only keeps the carbon down, but importantly raises the octane to the 92-94 level. This was the level of regular gasoline, at the time when the engine was developed.
My modest proposal is if you can't use the MMO, throw some diesel fuel in the gasoline to raise the octane, and maintain a burn.
Other side effects could be its effect on this ethenol addition to the gas. So far it's kind of a negative.
If I wasn't prohibited from self fueling at my yacht club, I would use a higher octane gasoline.

[Newenglandah]

I found the same issue with my flame arestor, I tried cleaning it with carb cleaner, it got some of the crusty green stuff out but not enough, so I used a soft wire brush nice and gently going with the grain of the induction fins, worked like a charm, it even shines nice and brassy

[Ajax]

If members are power tuning the Atomic they maybe overlooking an important element, octane. Adding MMO not only keeps the carbon down, but importantly raises the octane to the 92-94 level. This was the level of regular gasoline, at the time when the engine was developed.
My modest proposal is if you can't use the MMO, throw some diesel fuel in the gasoline to raise the octane, and maintain a burn.
Other side effects could be its effect on this ethenol addition to the gas. So far it's kind of a negative.
If I wasn't prohibited from self fueling at my yacht club, I would use a higher octane gasoline.

Hm, good stuff in here. I'll remove and clean my flame arrestor.

Sony- Surely you can carry fuel cans down to your boat, depart the marina, and fuel at anchor somewhere calm? How can the marina prohibit you from carrying "extra" fuel for a trip that you may be embarking on?