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[VintageLambo] Carburator rotary valve for crankcase fumes

Christensen

Hi George and Mike, The rotary valve is inserted in the flexible hose connection from the crankcase vent-hole to the intake-manifold vacuum-side. ( to burn crank-case fumes ) As I understand it, the function of this valve is to cut-off the connection when the engine is at idle/slow speeds. ( may be the reason some Lambos smells oily when runing at idle when hot ) Reason is that at slow engine speeds ( almost closed carburator butterflies ) the vacuum in the intake manifold is high, higher than required for this issue, and this could create a vacuum also in the crankcase, and furthermore you would also loose good vacuum to the brake booster when you really need it. Eventhough the crankcase itself would not experience vacuum ( it is vented at the cylinderheads ) dirty air would be sucked in ! At a visit to the factory ( during the Murcielago official presentation ) I found an Espada engine beeing overhauled, and took the liberty to ask the mec"s about this issue ( which had me puzled durrng the rebuild of my own Espada engine) Funny thing was that nobody there knew what good this rotary valve was for : they simply put back the things again as it was before. However my question got them wondering, and since the engine used as example had not yet been disassembled, we managed to trace the connections and make our assumptions, as stated above. best regards Lars ----- Original Message ----- From: Mike Dodge To: VintageLambo@yahoogroups.com Sent: Saturday, March 20, 2004 1:03 PM Subject: [VintageLambo] Re: Urraco carburetor mystery Hi George, The rotary valve you refer to is a sort of emmision/crankcase ventilation system that should be hooked up to the vent pipe running up the back of the engine to the aircleaners and then to the vent pipes above the trumpets. From Memory there is a small pipe fitting on the rear aircleaner vent hose pipe connection and the small hose runs along the back of the engine to that valve. From the valve it connects to a small fitting on the rear head right next to the sparkplugs and a balance hose then connects this to the front head in the same location (near the aircond pump mounting if fitted, mine wasnt so it was very easy to see). Both heads are drilled lengthwise and then smaller holes from this drilling go into the intake port just above each inlet valve. You can see on the head casting the longitudinal "manifiold" with an allen plug at each end of the head. When the throttle is above idle the rotary valve then allows oil and combustion by products to get drawn in to the engine much like the exhaust gas recirculation on so many US market cars!! Cheers Mike throttle- controlled air valve at the back of the Nos. 1-2 carburetor. Looks > like a vacuum cut-off of some kind, like on my Espada"s emissions > system. Old photos of the car in "original" state show it not > hooked up at all. What"s it for? Do I need to hook it to anything? > > Thanks - George Bullwinkel ------------------------------------------------------------------------------ a.. b.. c..