I think you can't go wrong with the original set up as far as crankcase venting is concerned..
It maintains a slight depression in the crankcase under the pistons.. reducing air pumping and pressure build up inside the crankcase caused by blow by gasses and the rise and fall of the pistons.. ideally there would be a total vacuum under the pistons thus increasing the pressure differential above and below the pistons.. but that would be impossible to achieve..
when a piston is on the down stroke the air trapped underneath it has to be shifted across to a piston on the up stroke . pumping losses.. so the lower the air pressure in the crank case the better.. hence the application of negative pressure or vacuum..
it also helps to reduce internal pressure on the oil seals..
The thinking behind the 'vent to atmosphere and catch tank' is that crank case blow by gasses do not contaminate the inlet charge.. theoretically more power.. especially if you are paying for very high octane fuel.. but of course you lose all the benefits of the above.. A catch tank is necessary because race regulations require that you don't dump oil on the track..so if you are trying to eek out the last drop of horsepower to win a race this may be the way to go.. And it'll keep your induction system nice and clean..
opinions are divided.. only dyno testing can prove one way or the other..
on a road car with no internal engine modifications.. I doubt if you would notice the difference..
Gettin' to old for this sh*t
Last edited by seadart; 24-12-13 at 02:47.