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Glider, No crankcase pressure up there? Put down the bottle and back away from the keyboard.How do you think the oil from the rockerboxes gets back down to the sump? Down the pushrod tubes thru holes in the tappet blocks and you are in the crankcase. Now the reason most triumph engine builders don't relieve the pressure at the rockerbox is you would then have air(pressure) trying to go up thru the holes in the tappet block at the same time oil is trying to drain down thru the same holes. Pretty much a conflict of interest. There are better ways and places to relieve c/c pressure,rockerboxs are used because they are easy,not good. Jack
 

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Bon, the return side of the pump is larger,that is true, but only slightly,and it dumps into your oil tank with only enough restriction to back some of the oil up to the rockers.I've had clear line on a rocker feed before and never saw enough air in the line to say it was significant. The pressure in your rockerboxes is Crankcase Pressure. It is the same pressure everywhere inside the motor that is connected to the c/c. Relieve it one place, it is relieved everywhere. The notion that air from the return side of the oil pump is causing leaks at your rockerboxes is IMHO wrong. Jack
 

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Bon, Haven't built the engine yet? That changes everything, if you want to do it right, research one-way valves. If plumbed correctly,you can get neg. c/c pressure and that equals less leaks and more power.It may not be much in the power increase,but every bit helps and it's "free". Jack
 

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Triumph changed the breather system in 78 (T-140E) to a "closed" system. The frame(oil tank) was vented to the EX. rockerbox,which in turn is connected to the sump,which is connected to the primary,and the primary is no longer vented right to the atmosphere but instead go to the airbox so fumes can be drawn into the motor to be burned. Jack
 
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