Eliminating the b*tch tube.??

[digger]

I have thought that the tube lets crank case pressure to enter head, whereas the holes at opposite side will drain oil back to pan. If crank case pressure should enter head only through drain holes, the drainage could be disturbed.

that is how it works its to let blowby from crankcase upto head to the VC breather, the drain back if the tube was deleted would only potentially be affected at high rpm when there is alot of oil flow so not much room for the air to use the same holes

[zaq123]

Don’t think it does anything for balancing crank case pressure as it’s a single hole. It will let pressure escape easier in general but not from front to rear which is what balancing does . As for how much flow it depends on the engine condition and how you drive it may not be missed. From memory 1 cfm is about most blow by you’d expect

the oil that drains down it will find the next easiest way. I’d need to have a look to see how big of a pool it would make but I’d think it would not be significant.

I wouldn’t delete it personally as my engine is not a low rpm, low hp new engine.

im sure there are ways to improve it, better quality orings would be a start so they don’t go hard as fast. Perhaps additional preload on the o-ring would help

1 CFM, is that it? Wonder why that tube was engineered so large? Considering crankcase pressure is about 6 psi, foot long 0.15" diameter tube can deliver about 4 CFM

[e30davie]

Not sure you'd want it any smaller or it would be even more annoying to remove/replace. A lot of nissan 90s engines suffer from oil pooling in the heads CA18det in particular and I think the RB series too. So the bigger the better when it comes head drains.

[digger]

1 CFM, is that it? Wonder why that tube was engineered so large? Considering crankcase pressure is about 6 psi, foot long 0.15" diameter tube can deliver about 4 CFM

yep that's what i measured coming out of the valve cover breather at about 7000rpm on the dyno

i doubt there is anywhere near 6psi crank pressure on a NA m20, maybe a inch or two of H2O

[dvallis]

The crank case pressure has to go somewhere. We fabled a bitch tube with 12AN outlet to a catch can but never used it. Just let crankcase vent to the head as intended. We have a 12AN fitting on the valve cover with a breather filter.



After some spirted driving with the new wing yesterday we noticed oil was puking from the valve cover filter. Makes sense since the new baffled oil pan is keeping pressure at 50 psi everywhere. We're adding a remote catch can to fix that. Might end up using the bitch tube vent to shorten the hose.