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Breather options, square-fin in an 850T frame

Sahms

Sahms

Cruisin' Guzzisti
GT Contributor
Joined
Oct 27, 2008
Messages
116
Location
Knoxvegas, TN
I searched, really. My old copy of Guzziology mentions a hi-po breather, but says it only works with motors that have the oil drain line in the bellhousing.

Probably no airbox. How to get the vapors out and the oil back in (I guess through the valve cover vents?).
 
Either that, which might be difficult with a stock or Ago box as it will be mounted below the heads, (or at least it's drain will be.) or do as on the later bikes and have an external return and plumb it into the sump.

Pete
 
Lets prepare the scene.

I´m sitting in a budget hotel in what used to be East Germany and I´ve had an Ein Pils or two. If I read insulting then I don´t mean to be but I do have a habit of coming across that way after a few so please don´t be thin skinned.

You need to understand what you have, where the air is supposed to go and why. Once you understand that you can make a breather system. Its easy peasy. The thing you don´t mention is which square block motor. Does it have the head breathers? Not all do and does it have pods? The fact you neglected to insert this indicates lack of understanding. (Remember the Pils!)

Unfortunately the big block motor was forced to have its breather flow in the wrong direction, against thermal flow. The one way valve at the bottom of the big hose breather ensures that. The small blocks, that came later had that rectified. There is an old wise saying, don´t try to push shit uphill but Guzzi tried to push hot air down.

The air will come out of the big hose fitting on top of the crank, valve enforced. Any breather box you make needs to have the air coming in just under half way. The oil return needs to be form the bottom and the vent line needs to be at the top. Simple gravity stuff. The vent historically went to the clean, lower pressure area of the filter box to help flow. If you have pods then it should be run as evenly high as possible to allow any oil to drain back and it should be filtered at the end.

Cheers

Rod who is happy with his reply as he is typng better than he hs a right to.
 
Morizzi said:
You need to understand what you have, where the air is supposed to go and why. Once you understand that you can make a breather system. Its easy peasy. The thing you don´t mention is which square block motor. Does it have the head breathers? Not all do and does it have pods? The fact you neglected to insert this indicates lack of understanding. (Remember the Pils!)

Unfortunately the big block motor was forced to have its breather flow in the wrong direction, against thermal flow. The one way valve at the bottom of the big hose breather ensures that.

The air will come out of the big hose fitting on top of the crank, valve enforced. Any breather box you make needs to have the air coming in just under half way. The oil return needs to be form the bottom and the vent line needs to be at the top. Simple gravity stuff. The vent historically went to the clean, lower pressure area of the filter box to help flow. If you have pods then it should be run as evenly high as possible to allow any oil to drain back and it should be filtered at the end.
Click to expand...

Sorry for my lack of understanding.

There will likely be no airbox on this creation. The motor is a 949 big-valve cali motor and does have the vents on the heads below the valve covers and does not have the small oil drain line to the sump that round-fins have next to the larger breather hose. The OEM setup used the frame as the breather, and drained the oil back into those valve cover vents, but those drains exit the frame at an elevation higher than the valve cover vents.

So I need a breather with three orifices, all of which have to be higher than the valve covers, since the lines to them will be lowest on the breather. The vapor outlet is highest, the vapor inlet is next-highest, and the oil drain is lowest.
 
Fred,

You might be OK with a chamber high on the frame and vented to atmosphere with a small filter. Better than no venting at all. Or with a little drilling and welding of fittings you might be able to replicate the CA III/California venting on the T frame.
 
A breather box is really an air/oil separator.

I don't know what Morrizi is on about with thermal this or that but Guzzi got it wrong with the roundheads - they put the Positive Crankcase Ventilation valve (indeed two of them) in the wrong place - between the crankcase and breather box and put the return line below the oil level of the sump. The net result was that if the PCV was shut or overwhelmed by blowby the oil would be forced out of the engine and onto your rear tire.

The square heads typically returned the oil via the cylinder heads so this is not a problem.

I would make a breather box - just a box with a connection for a pipe from the crankcase,a return(s) at the bottom that lets the oil drain back into the engine and a pipe to atmosphere. The pipe to atmosphere should have a PCV valve on it - this lets hot oil air out and stops cold wet air going in and causing mayonnaise. You can increase the efficiency of the breather box by stuffing it with stainless steel wool or like. Design it so the air does not short circuit the air/oil separator part i.e. it passes through the steel wool before going to atmosphere.

The bigger the box the better. The Ago box is just a bigger box and not really worth the money IMO.

In the squarehead frames typically the frame itself is used as the breather box - and why not? Its there, has lots of capacity and IF you fit a proper PCV valve (a filter is better than nothing but not as good as a PCV valve) will stop the frame from rusting as it is continuously oiled.
 
Chris R said:
I don't know what Morrizi is on about with thermal this or that
Click to expand...

Most people don´t. It doesn´t mean I don´t know what I´m talking about. Ponder me this. Why does a big block Guzzi get fitted with one or two directional valves when the small block motor doesn´t have any?

Please don´t degrade my replies unless you have the undertanding. I thought I had done really well considering the state I was in. I´m no longer drinking Pils, I´m in Poland and drinking Pivo.

Hot air rises, cool air falls so why does Guzzi try to force the hot air at the top of the heads back down to the crank case? Try plumbing your car radiator in reverse and see how long the car copes.

I´ll leave you guys to it. Ego seems to be more important than knowledge here.

Bye

Rod
 
Don't go away mad! Geeze! I take it you're not the happy kind of drunk.

Yes there's heat, but there's also crankcase pumping pressure and gravity involved. The valve cover vents are unvalved, while the big crank vent has a check valve. Any pressure in the valve covers will be greater that any heat-related rising, and the hoses to the valve covers for square fins also carry oil back into the motor (via gravity). I don't see how a breather that's open to atmosphere would "force the hot air at the top of the heads back down to the crank case".

Anyway, I think I'll try to fabricate something that will fit under the tank. I'll have to figure out an alternative coil location, but that can be done.

Thanks for the input.
 
I´m not mad, not even miffed, I´m just tired of those with poor understanding fobbing me off. I had a chat on this subject last year with Dave Richardson. I asked him to include a bit of this in the next version of Guzziology.

If you look at my user name the first few letters are from Morini. They didn´t have any direct oil feed t the valves, it was all by oil mist via the breather system. If you didn´t understand it and changed it then you were in a very high risk of destroying it. True, I´m not being dramatic.

Simply the breather system of the small blocks runs in the reverse direction to the big blocks. ie it runs logically. Hot air comes out of the highest point, just like a chimney, via the rocker breathers. The thing that stops Big Blocks doing this is the PCV. As it is a gravity controlled device it just can´t be turned upside down but if it was replaced with a flapper or reed valve then logical flow can be achieved.

Total flow reversal isn´t essential really because big blocks were never designed to utilise this flow, small blocks differ here. Just try and keep to normal thermal flow for the heat and gravity flow for the condensating oil and you won´t be too far wrong. Just keep in mind the one way valve in the system.

Sorry to confuse others with thermal flow this and that.

Rod, didn´t read it in a book but worked it out because he had to.
 
So I need a breather with three orifices, all of which have to be higher than the valve covers, since the lines to them will be lowest on the breather. The vapor outlet is highest, the vapor inlet is next-highest, and the oil drain is lowest.
Click to expand...

Three pipes coming out of the breather box is optimal but you can return the separated oil via the main breather line if you wish- the only thing is to make a shield so the oil doesn't get flung on the crank on its return home. The mass and velocity of the air is trivial compared to the mass of the oil plus gravity. There are quite a few engines that work this way.

Rod, can you send me a case of what you are drinking? There wouldn't be any Peyote in Pivo?
 
Chris R said:
Rod, can you send me a case of what you are drinking? There wouldn't be any Peyote in Pivo?
Click to expand...

So Chris, no answer to my question just subtle put downs.

I´m not surprised. Its why I post very little these days.

Bye
 
Interesting subject for me as I am currently putting 1100 carb sport motor into a 850 T frame.

Some time back in the late 90's I had a hotted up LM3 with 92 mm bigbore kit (1040cc) For the breathing I drilled and tapped the heads for the breather line fittings and installed a Agostini breather box,making the breathing just the same as an early Tonti, ie with oil drain to the sump etc.
Well it worked ,it never spat any oil from the breather box,didn't leak any where.
I sold the bike 18 months ago and the last time I spoke to the owner all was well.

The Sport project has a similar problem with the breather and fittings.So what worked before should work again.But this time I have had to more machine work.The oil line fitting at the bottom of the bell housing has been machined to accept the early oil drain,the top of the crankcase where it is blanked off has been drilled to suit,the heads will get drilled and tapped for the fittings,plus I will install a Ago breather box.
I have had chat with Pete Roper who thinks the system may not cope,but the way I see it is the engine capacity is about the same 1040 vs 1064cc so I think it will.I will aslo install one of Pete R Windage plates too.
Brett
 
Some time back in the late 90's I had a hotted up LM3 with 92 mm bigbore kit (1040cc) For the breathing I drilled and tapped the heads for the breather line fittings and installed a Agostini breather box,making the breathing just the same as an early Tonti, ie with oil drain to the sump etc.
Click to expand...

The roundhead engines had the return going to below the level of the sump which was the main problem - I imagine the engineer thought this was some sort of smart one way valve. If you put your thumb over the main crankcase vent, the crankcase will pressurize up and force oil up the pipe until the oil level falls below the level of the pipe inlet.

This only happens if the valve is stuck closed or the rings go south and the valve becomes an impedance. I have seen this happen on the road with disastrous results.

The square fins corrected this by returning the oil via the heads. The only mistake Guzzi made this time was not sticking the PCV valve where it should be - to atmosphere. The breather box in frame of the square heads is IMO a good thing. Just move the valve to where it should be and the mayonnaise will disappear immediately - as it has on my lemans1000.

Pete's plates are a good idea and help from a number of fronts including controlling slosh so the oil pickup does not get uncovered.

Ta,
 
I modified the frame (Convert frame) to have a breather in frame just like the later big blocks have.. if you look at a newer frame it will be easy to copy that breather by putting a couple holes and fittings on frame.
DSCN1553.jpg
 
For those of us that don't have access to a newer frame, would you be interested in explaining exactly what you did? I'm just in the process of putting an old T together and wouldn't mind making this addition to the bike while I have it apart. Thanks, Chad.
 
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