Rocker cover breather size for 20+psi boost?

[garth]

what size rocker cover breather vents are to be used, and what (if any) catch cans are available off the shelf that work?

I have been using the standard nissan 8mm vent and a Simota catch can and both appear to be woefully inadequate.
The engine has no blow by at idle but will need to breath at revs.

Prefer not to put hose into chassis rail for 'automatic rust control'.....

regards Garth

[NutterGQ]

you cant make it too big so fit a couple of big brass barbs and go from there, with the catch can the biggest prob with most off the shelf ones is they dont have any filling so they dont hold onto any vapour and therefore may as well not be there, so if you buy of the shelf make sure its openable to get some coarse steel wool or similar in there. Also cheap china ones have small pre fitted barbs, i just cut a tube of alluminium stuffed it with steel wool and tiged a flat piece in the middle nearly to the bottom and put 2 caps on, big barbs on top and your done.

[garth]

thanks nutter, have seen the 3 vented chamber ones with a drain also so looks like i'll have to make my own.

From memory are the GQ rocker covers double skinned? if you drill through to fit larger fitting - swarf will be trapped between the layers and will end up in the engine......?