The testing that virtually everyone has done...with the factory rocker box vents...has been totally ass backwards. They have all been testing how effective the rocker box vent tubes are...as passive vents.falcor wrote:At the time of the incident I only had a single line from the port on the oil filler box to the drivers side air filter.
I had read somewhere that Jake Raby and someone else had done tests and found the vents on the rockers wasnt needed so I simply plugged them up. Obviously this wasnt a good choice so I'll hook some sort of system up again.
With that I'm hoping the leakage should be solved. Right now I'm chasing the source of the sound.
Meaning they have this totally illogical expectation that gasses that blow by the rings are naturally going to make their way down to the pushrod tubes...and go up into the heads to find that vent tube. And...attaching the hose to the air cleaner...virtually any air cleaner unless its a tuna can sized restrictive enclosure...gives virtually "0" vacuum. I know...I have measured the vacuum at various ports in various air cleaner enclosures and rarely found more the 1hg of vacuum inside except at the very edge of the TB tube....unless they are very restrictive.
The factory system was designed as pull through with manifold vacuum and worked very well. A single tube to the oil vent box...only really works well...when case pressure builds up to push gasses out. With the low vacuum generated by just venting to an air cleaner enclosure....it would vent better by having an inlet into the case some distance from the outlet...to allow air to be pulled into to help gas move out.
As for the sound...man I just don't know. If for some reason the blow by gasses were very rich and it got ignited in the valve cover...this would do it. The ignition point is usually from the air cleaner end...because there is potentially some air fuel there if you have reversion on deceleration.
Its not unheard of....and is the exact reason the factory installed a flame trap in the junction point of the two hoses that feed the rocker box vents and pull from the air cleaner in the stock system. The part # of the flame trap 022 129 961. There is also an anti backflash baffle in the air cleaner where the two vent hoses pull air from.
This is even more risky on a low velocity PCV vent hose system. Without manifold vacuum..crankcase gasses just kind of ooze up the hose.
Bet you had a back flash through the vent hose. That would pressurize the whole case...causing one or both valve covers to lift. Ray