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MG MGB GT V8 Factory Originals Technical - Rover P6 valve covers: breathing?
|Guys, I found a really beautiful set of Rover P6 valve covers -- powder coated gloss black with the ribs polished -- going to swap 'em in there in place of my ugly SD1 covers. I was wondering whether, for breathing, I could just clip a small open breather filter (the K&N kind that you see on Minis) onto each cover's breather tube (on the P6 covers there's a 1/2" tube sticking up at an angle out of the middle of each one). Would that result in my pristinely detailed engine bay getting covered in oil mist? If so, maybe I should put the breathers down next to the bell housing and connect 'em with hoses? (I don't really want to run a PCV setup because I have had repeated problems with doing so in the Rover V8 -- no matter which PCV valve I use, it sucks out too much oil, and I can't seem to get it right.)|
|I installed my Rover 3.5 into my MGB last winter and drove it all this summers driving season. I purchased 2 flame Traps from Mr. Gasket which fit into the existing rocker cover pre drilled holes, no hoses as per the original set up and no PVC valve, never noticed any oil misting in the engine compartment. I did have a persistent problem with oil leaking past the rear seal in my newly rebuilt 3.5 Rover. Couldn?t tell where it was coming from, I replaced the oil pan gasket several times and finally and in July (2 months after putting it on the road) I replaced the rear main rope seal with a neoprene one, it still leaked. I finally pulled the engine and replaced the frost plug behind the cam and still it leaked. I finally drilled a hole in one of the chrome flame traps and installed a PCV valve which draws the air from the rocker cover (dropping the crankcase pressure) and goes to the carb via a rubber hose. Voila, end of leaking rear main seal. Still looks good and doesn?t leave pools of oil everywhere I go|
|The V8 roadster i used to own had a P6 bottom end, which if i'm not mistaken had a breather at the back of the engine. I'm currently rebuilding another v8, which is going to use a sdi block and P6 covers - i think i may need to drill and insert the breather at the back of the block to get round this problem. Hadn't given that one a thought.|
|Thanks guys. Sounds like I oughta learn to live w/a PCV valve. Maybe if I make a baffle that will help the oil consumption. I was thinking as follows: on each valve cover, there's a 1/2" breather tube, about an inch long, coming up at an angle. What if I just plugged the top & bottom of that tube with epoxy, and then drilled offset holes, say 1/16", through those epoxy plugs? That way the PCV rig could suck some of the air out, but not allow much oil to splash up and out. Would that help? ... and will epoxy take the heat OK without melting?|
|The Rover V8 setup is supposed to have each valve cover linked to one of the twin carbs - this draws fumes out of the engine. There is normally a vent on the back of the engine (as Ian says) connected to something that looks very like a fuel filter but which is actually a restrictor, that is the air *inlet* to the block. There ahould be flame-traps in between the valve covers and the carbs. Those and the restrictor should control the amount of through-flow and hence oil loss.|
|Just to clear a couple of things up, I do have a tube at the back of the engine which goes into the lifter gallery (valley) this I connected via a rubber hose to the recycle canister located on the passengers firewall. |
The carb I am using is an Edelbrock 500.
Before I installed the PCV valve I could see fumes coming out of the Flame trap on the passengers side, so I am assuming that the flame trap on the drivers side was taking in air and the passengers side was expelling it.
But Paul is right, the original set up was each valve cover linked to one of the twin carbs
|On any engine, the breather system should allow fresh air in, oil fouled air out. If you plug everything tight, pressure will develop, resulting in oil leaks in various areas, such as around the base of the distributer, front & rear crank seals, etc. The PVC valve is the "exhaust" end of the cycle, providing an outlet for hot, oil charged air. Venting it to the atmosphere does add to air pollution, so gennerally, it is vented to the air cleaner, so the oil in the air goes through the combustion process, reducing the air pollution. For this process to work, the PVC valve is a one way valve, allowing the gases to exit only. Next, you must have a source of incoming fresh air to provide for circulation. One rocker cover may have a hose to the air cleaner, the other just a filter to provide fresh, clean air to enter the crank case. On early engines with a rear intake of fresh air, hoses from both rocker covers can be vented to the carb(s). On later valve covers, there is a small "mushroom" which is the intake, a flame trap with hose which is the outlet.|
It really cost nothing to vent the crank case exhaust in a way to reduce polution, it does not hurt performance, & that is my recommendation, rather than just venting to the atmosphere.
This thread was discussed between 03/01/2002 and 05/01/2002
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