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MG MGB GT V8 Factory Originals Technical - Rocker Cover engine breather hose
|Hi, At present time my rocker cover engine vents are venting into bottom of pancake filter for Holley carb. Im looking for a way to vent them elsewhere as im sure the hot fumes must affect temp of intake gases. ie. lower hp. Ive got RV8 exh. manifolds going through inner wings. Has anyone experience of venting them straight into wheelwells, or into exh.manifolds using a non return valve?? Would this unsettle the engine in respect of ?closed induction system? Danny.|
|D R Smith|
The Rover V8 needs positive crankcase ventilation or it will build up internal pressure, in mine when i tried to vent to air it was causing oil to be pushed down the valve guides. Real Steel recommend what you have ie; one vent pipe from one rocker cover with a pcv valve inline into the air filter, the other cover should have a small filtered vent to allow the system to balance itself.
Hope this helps.
|Thanks Kevin, Mine has both rocker cover hoses going into a T junction, then into base of air filter housing. No valve in either? I kinda remembered somewhere people talking about venting straight to exh manifolds using a non return valve, mustve been when i had Lotus Elan? So are you saying that there is no other option other than routing hot engine fumes into carb inlet? Maybe i should concentrate on getting a good supply of "cold" external air to carb. Danny.|
|D R Smith|
You have to get some vacuum to vent the crankcase and the airfilter base is the preferred option on a carburetted engine, cold air to the carb woudn't be a bad thing but it is important to have a PCV valve in the pipe between rocker cover and air filterand the small air filter on the other cover.
You have mail
|Seems to me I remember in the past some folks talking about venting crankcase pressure to the exhaust with inline check valves - perhaps the archives. I have seen this done to drag race engines years ago, but I don't believe that there is a successful arrangement for the street.|
I don't think that venting the crankcase to the air filter housing has enough vacuum for a pcv valve to do much good. I think I would just use an in-line orifice, about 1/8 to 3/16 diameter in the line. There has to be somewhere for make-up (fresh) air to get in the crankcase, so unless the oil filler cap is vented, teeing both valve covers together won't work properly. And in the grand scheme of things, the amount of air from the crankcase diluting the fresh intake air would be so small that you probably couldn't detect the HP change.
|Hi, Thanks for comments. Wayne, are you suggesting what i used on carb intake to my 5GT Turbo to increase boost. ie. that i drill a small hole at some point(tee piece?) My oil filler cap is an aircraft alloy machined item which has no vent, so as far as i can see there is no facility for crankcase to get fresh air at present. The hoses are goodrich braided types large bore. Are people suggesting that one rocker cover should have negative pressure and one positive? Danny.|
|D R Smith|
|I'm suggesting that a plug of some sort with a hole drilled through it be inserted in the vent hose going from one valve cover to carb air cleaner housing. The other valve cover will need a filtered air inlet, such as those at http://www.knfilters.com/vent.htm .|
|I'm with Wayne, a pcv is designed to work with engine vacuum. Using it on the air filter side is not correct. |
I use the repro MG V8 valve covers. I pulled out the vent tubes, threaded the holes, & installed 90s for carb clearance. One side goes to the air cleaner base, the other side goes to a pcv then on to an open vacuum port at the base of the carb.
This link has a pic of how it works:
|Thanks guys for informative comments and links. I had to change a couple of inlet valves last year due to mushrooming/binding with blueing of valve stems. Wouldnt be connected would it? (PO had sprinted the car.)|
|D R Smith|
This thread was discussed between 27/06/2005 and 28/06/2005
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