Bruceynz
Well-Known Member
So the breathers only will allow pressure to build up and I will get oil leaks?
here are the valve covers I bought
here are the valve covers I bought
Heater Noise
- Thread starter Bruceynz
- Start date
kkritsilas
Well-Known Member
The breathers allow pressure to leave the cylinder heads without spraying oil all over the place. You will not have pressure build up in the cylinder head area below the valve covers. You may get pressure build up in the crankcase.
Depends on if the hole that the PCV valve was connected to is blocked off. If you did block it off, crankcase pressure will increase. The pressure increase may nor many not be enough to cause a leak. Depends a lot on how much blow-by the engine has, what kind of rpm the engine is running at, and an a number of other factors. Won't do the oil any good anyway. If you didn't block it off, where/how is the crankcase being vented? If it is being vented below the car, You will smell it. You also may be spraying out a small amount of oil.
Most valve covers have holes near each end, with one hole open (usually for one breather and the oil fill hole/cap), and a pair of caps to allow for a second breather and the PCV valve grommet.
See: (Stolen from Summit's site)
Depends on if the hole that the PCV valve was connected to is blocked off. If you did block it off, crankcase pressure will increase. The pressure increase may nor many not be enough to cause a leak. Depends a lot on how much blow-by the engine has, what kind of rpm the engine is running at, and an a number of other factors. Won't do the oil any good anyway. If you didn't block it off, where/how is the crankcase being vented? If it is being vented below the car, You will smell it. You also may be spraying out a small amount of oil.
Most valve covers have holes near each end, with one hole open (usually for one breather and the oil fill hole/cap), and a pair of caps to allow for a second breather and the PCV valve grommet.
See: (Stolen from Summit's site)
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Bruceynz
Well-Known Member
Why I ask about the leaks is mine is leaking oil!! So I wonder if thats why?? I did a rear main and RTV the oil pan gasket up good and proper and still leaks! Annoying!
kkritsilas
Well-Known Member
Bruceynz:
It is close to impossible to say either way. Did you block off the place where the PCV valve used to connect to? Even if you did, as I said above, it is hard to say categorically whether this is the problem or not. Keep in mind, however, that there are very few engines that are completely sealed in terms of allowing zero blow by (the engines with zero gap pistons are closer than engines that use conventional pistons, but even they allow a small percentage through). Blow by is the part of the fuel/air mixture that is burned by the engine that makes it past the pistons down into the crankcase. It is under pressure, and thereby pressurizes the crankcase. Crankcases are vented for this reason (either by a vent tube or by a PCV valve). Again, I am not saying that this is reason for your leaks, only that it is one possibility. Leaks caused by lack of crankcase ventilation would be from the oil pan/lower part of the engine.
If you have blocked it off, try putting on a vent tube, and see if your leaks decrease or stop. If they do, then you can stay with the vent tube, or look at putting the PCV valve system back. As has been mentioned before, cars that used vent tubes have a tendency to smell bad, both inside and outisde the car.
Just as a side note, and really has nothing to do with our cars, but high perfromance 4 cylinder motorcycle engines have started to add holes between cylinders to allow for equalization of crankcase pressure between teh cylinders. The theory is that, due to the very high rpms being turned by these engines, the air in the crankcase cannot move down the cylinder fast enough, and is causing resistance to the pistons that are moving downwards. They put these holes fairly far down the cylinder bore, and when the piston starts the move downwards, the pressure behind the piston is actually dumped into the adjacent cylinders, of which at least one is moving upwards. There is actually a small, but measurable power increase with the holes in place.
It is close to impossible to say either way. Did you block off the place where the PCV valve used to connect to? Even if you did, as I said above, it is hard to say categorically whether this is the problem or not. Keep in mind, however, that there are very few engines that are completely sealed in terms of allowing zero blow by (the engines with zero gap pistons are closer than engines that use conventional pistons, but even they allow a small percentage through). Blow by is the part of the fuel/air mixture that is burned by the engine that makes it past the pistons down into the crankcase. It is under pressure, and thereby pressurizes the crankcase. Crankcases are vented for this reason (either by a vent tube or by a PCV valve). Again, I am not saying that this is reason for your leaks, only that it is one possibility. Leaks caused by lack of crankcase ventilation would be from the oil pan/lower part of the engine.
If you have blocked it off, try putting on a vent tube, and see if your leaks decrease or stop. If they do, then you can stay with the vent tube, or look at putting the PCV valve system back. As has been mentioned before, cars that used vent tubes have a tendency to smell bad, both inside and outisde the car.
Just as a side note, and really has nothing to do with our cars, but high perfromance 4 cylinder motorcycle engines have started to add holes between cylinders to allow for equalization of crankcase pressure between teh cylinders. The theory is that, due to the very high rpms being turned by these engines, the air in the crankcase cannot move down the cylinder fast enough, and is causing resistance to the pistons that are moving downwards. They put these holes fairly far down the cylinder bore, and when the piston starts the move downwards, the pressure behind the piston is actually dumped into the adjacent cylinders, of which at least one is moving upwards. There is actually a small, but measurable power increase with the holes in place.
Oil leaks will happen, period.
When engine oil is running down the inside of engine (which should be normal) and it runs by a potential leak. If the crankcase is pressurized it will push the oil out of that leak area.
If pressure is equal to or at a vacuum – there is no force to push the oil out, it simply keeps running down to the pan.
The breather is dual purpose. It allows intake of filtered air – in direction of PCV valve and generally breather is on opposite sides of PCV. It doesn’t have to be but does create air movement side of crankcase (a good thing). If an engine has excessive blowby (gasses going past the piston rings) then anything the PCV is not able to recover - the excess goes out the breather.
A test I’ve seen done when trying to determine blowby in excess is to remove the breather (with PCV valve in operation), put a load on engine (power stall, dyno, etc.) and with a piece of paper (or air flow meter) monitor the paper on the hole (or with meter – measure the air flow). An engine with good piston ring sealing should have a vacuum on the breather port or will be neutral.
Pressure will push the paper away from breather hole.
Having some pressure is not a problem as long as it is only when engine is under a load.
Excessive pressure means cylinder rings are not sealing and one needs to review their options.
When engine oil is running down the inside of engine (which should be normal) and it runs by a potential leak. If the crankcase is pressurized it will push the oil out of that leak area.
If pressure is equal to or at a vacuum – there is no force to push the oil out, it simply keeps running down to the pan.
The breather is dual purpose. It allows intake of filtered air – in direction of PCV valve and generally breather is on opposite sides of PCV. It doesn’t have to be but does create air movement side of crankcase (a good thing). If an engine has excessive blowby (gasses going past the piston rings) then anything the PCV is not able to recover - the excess goes out the breather.
A test I’ve seen done when trying to determine blowby in excess is to remove the breather (with PCV valve in operation), put a load on engine (power stall, dyno, etc.) and with a piece of paper (or air flow meter) monitor the paper on the hole (or with meter – measure the air flow). An engine with good piston ring sealing should have a vacuum on the breather port or will be neutral.
Pressure will push the paper away from breather hole.
Having some pressure is not a problem as long as it is only when engine is under a load.
Excessive pressure means cylinder rings are not sealing and one needs to review their options.
Nice looking engine bay!
