Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Front crankshaft? oil weep

This entire project for the for the catch can /tank vent is an experiment. With the tank vented the cam chest is not spitting up oil.

Now to get the frothing of the oil in the tank contained. It is a work in progress.

Stephen:

does the hose that enters the side of the breather come off the crankshaft vent?

Currently the crank case breather goes into the side of the bung that holds the oil tank cap, it is factory install. The breather is coming from a drilled and tapped oil tank cap going to a catch can.

I am doing an experiment today to see where the foam is coming from, I am thinking it is coming from the crank case breather but today will tell the tale. If not there it must be coming from the return line from the engine pump.

I am getting zero cam chest puking of oil with the tank vented, only condensate of water mist, like a light fog.

The foaming oil is coming from the return line from the pump. The movement of air from the big pistons moving up and down and engine blow by are creating foam in the oil and that internal pressure is trying to push up into the throttle body from the cam chest. With no tank pressure the cam chest vent is devoid of oil.

The crank case breather has no oil spitting out of it.

It was ever thus with dry sump engines. The scavenge pump has a higher capacity than the feed pump so the sump will not flood, but this means the return pumps a mixture of air and oil - hence the foam. On the old brit bikes that used this system the return line went into the bottom of the oil tank so the foam was dissipated into a few bubbles and the tank did not froth up too much.

John

I've only had a few Brit bikes, but all had the return line coming in the bottom of the oil tank, but with an internal pipe which had it's top above the running oil level. To reduce wet sumping when parked, I imagine.

In any case, foamy oil coming back into an oil tank that has a capacity 50% greater (6qt vs 4) than recommended by S&S should not be a concern. There is plenty of time for the air/oil to separate in the upper levels of the tank before being pulled into the engine from the tank bottom.

Personally, I don't see the need to change a perfectly functional PVC/breather system that discourages oil leaks via negative crankcase pressure. IF one suspects that the crankcase is being overly pressurized leading to oil leaks, I would first look for excessive blow-by, a plugged orifice in the cam chest to intake breather line, or even simply overfilling the oil tank. With systems such as used by S&S it is imperative to maintain adequate airspace in the oil tank to allow for pressure equalization between the engine and oil tank (S&S specs a minimum of 1 qt of airspace). When having a new oil tank built for my machine I specified a longer tank, providing an additional quart of airspace.
Can't say if that improved things, as my engine doesn't leak, but as there was plenty of room for a longer tank it seemed prudent to increase the air capacity against the eventuality of future engine wear/blow-by.

Steve, if the breathing system was working properly then why is it puking oil up into throttle body?

I get it that the large oil tank allows the foam to turn back to oil because of its large volume. I get zero oil out of the cam chest vent without the throttle body sucking on it.

Is one reason it is done that way, to dump oil into the throttle body, a method of lubricating the valves?

I'm not saying that YOUR breathing system was working properly. I am saying that the breathing system, as designed, works just fine. Therefore, if significant quantities of oil are making it's way into the throttle body, then something else is amiss. There should be a .100" restrictor in the pipe between the cam chest and intake, and if that is missing or somehow loose I imagine you could see fairly large quantities of oil in the intake. And as mentioned my earlier post, excessive blow-by could contribute as well.

The purpose of the vent into the throttle body is not valve lubrication, but rather to create negative pressure in the crankcase by exposing it to the low pressure of the intake tract. It also aids emissions compliance by routing oily air into the engine to be burned rather than pumping it into the atmosphere as was common before the mid 60's. Two birds with one stone, though not sure which bird drove that particular design decision.

The S&S X-wedge appears to be a pretty good design, crankcase breathing wise, with a large crankcase airspace, very large pushrod tubes which allow for air shuttling movement between crankcase and rocker area, and the relatively large airspace in the oil tank creating an effective additional buffer. The pressure in a running engine does not cumulatively build up so much as it just moves (rather violently) from one part of the engine to another. It should only take a modest amount of vacuum from the intake to maintain an overall negative pressure in the system.

It is normal, but somewhat bothersome, that a properly functioning PCV system will admit a small but noticeable quantity of oily mist into the intake tract, and in extreme cases can lead to valve deposits. Because of the M3W's injectors being fairly far downstream in the intake ports, combined with the side draft, vs. downdraft throttle orientation, there is not the natural intake tract 'washing' effect one would see in a more upstream injector placement.

While I've only had my M3W for two years now, I do not find the oily mist to be excessive at all. When I removed my intake system in 2018 to facilitate cam follower cover replacement (at about 8k miles), I was a bit surprised at the buildup of oily grunge film in the intake manifold just past the 'split' (maybe .050" thick) so I detail cleaned all the intake parts while they were off. As I'm not the original owner, I'm not sure if the grunge buildup was due to the breather system and/or an overly oiled gauze air filter, which given how it was when I got the car is a possibility. Since then, I remove the air filter and spritz the intake system with carb cleaner before my last drive before the season end oil service, and that seems to be be working well.

Thanks Steve, I suspected that to be the case.