Flametrap and vent pipework for crankcase breather

[Objective]

Addressing our 1971 TC 2000 crankcase breather 'system', all joints were loose and some rubber piping has turned to mush. What I found was a flame trap (photo) that seems completely blocked (I cant blow through it, let alone see daylight through it!) and a completely blocked carburettor inlet (photo) - can't tell yet whether the blockage is perished rubber or crud from the crankcase. The flame trap isn't freeing up with petrol (not so much 'flushing' as 'bathing') and clearly the whole system needs replacing.

I'm tempted to forget negative crankcase pressure for a time while I rebuild the carbs . . . sealing the carb inlets and directing the crankcase vent via a filtered capture tank. I'll rebuild and rebalance the carbs and run up some kilometres to see if anything gathers in the capture tank and reassess how the engine's running goes.

Has anyone got any comments on this plan, which I recognise isn't keeping everything 'original'. Is the pressure generated by the carb feed really significant, since its not been contributing for some time!

 

[colnerov]

It is crud from the crankcase, Carbon from combustion that has got past the rings. I used to use a thinners bath although not 100% it got most of it. More recently I was put onto BBQ and oven cleaner, leave to soak for 10 to 15 mins then blast it through with a pressure washer. Any particular brand will do if it has Sodium Hydroxide (the active ingredient). I used it recently on an engine rebuild and it brought up the block and heads like new. The carb port can be cleaned out by mechanical means, i.e. a screwdriver or a drill bit.

Colin

 

[Objective]

Hi Colin, thanks will try BBQ and oven cleaner next (the flame trap is laughing at my current efforts!)
Also get onto scraping with sharp metal object to clean out the port (& interior of the box).
UPDATE, I follow Michael (Redrover) who does excellent writeups of his immaculate work. Stumbled on this post from 2012! , and I find I agree . . .
"

- why did you choose not to connect the crankcase ventilation to the carbs?

Because they aren't really necessary any more, and it's just adding unnecessary variance to an area that needs to be as precise and unvarying as possible: carburetion.
Crankcase ventilation was just a way minimize the amount of 'potentially harmful' gasses escaping from the engine in order to make the engine comply with some arbitrary figure in a now long outdated set of environmental regulations. Pre 1971 P6's didn't have the system at all, and I figured that since the carbon monoxide escaping from my non-catalysed exhaust far outweighs the quantities of 'potentially harmful' blow-by gasses that might find their way into the crankcase, there's no reason why they need to be burned with combustion any more. As long as you don't breathe them, you're alright, so I routed some pipes away beneath the engine to either side of the bell-housing where get wafted away without issue. Very occasionally, I will get a small drip come out of one, but nothing more than that.

The real advantage is that they no longer spew oily, filmy, horrible dirty air straight into the carb. This can cover the throttle disc, the back of the piston, presumably coat the inlet ports to upset swirl, and crucially introduces a variance in the atomising of fuel. When the engine is at higher speeds, there is greater crankcase ventilation, and therefore more 'bad air' being forced through the pipes. When faced with the choice of pressurized air from a tube, or atmospheric pressure air on the other side of a carburettor piston, the carb will suck from the tube every time. But because this varies so much with engine speed and condition, and because the carbs are connected to different crank case tubes, you're chasing a white rabbit trying to get the damn things in tune. Blocking up the pipe inlets (as I have done since this picture with a silicon sealant and steel 'bung') means that all of the induction air comes over the carb bridge. It runs a little richer now, so I'm thinking about a different needle choice, but the performance is much quicker and much, much smoother to idle."

Love to hear contemporary comments.
Paul

 

[quattro]

The system draws dirty contaminated air from the engine and burns it.

Apart from any environmental issues, it helps to keep the inside of your engine cleaner, thus it will last longer. Driving around for a few hundred miles isn't going to give you any idea on its performance. You need to have two identical engines and drive them around for a year or so, one with it connected, one without, then strip them down and inspect them - can't see anyone doing that

I wouldn't drive around without it working on my engine

 

[Objective]

Thanks Quattro, all good points. - Regarding the test miles I was thinking more about the state of the engine tune rather than the state of the engine without the system connected. After servicing the carbs (scraping out the varnishes fed into the airbox) and running well balanced carbs, I'm hoping to get more consistency in the state of tune. Certainly it seems my negative crankcase pressure system hasn't been working for some time, and I take the point made by Michael about reducing the variables while re-tuning, which could be beneficial.
There is also the argument for reducing engine leaks at seals. Does anyone have an idea of how much negative pressure is generated in the crank case, and/or the intended volume of gas outflow from the crankcase ?
Are there really environmental issues? Sure the by-pass air via the crankcase isn't healthy, but perhaps limited via a vented trap tank. Maybe in comparison to the overall effects of running a 53 year old car, the more accurate tuning of the engine would compensate somewhat.
This is a great forum for discussions though, so all comments very welcome of course.