i cant find what size bung i need for a catch can coming from the valve cover i want two feeds no return.

 

I have read many use the common 10AN size (5/8"). I am building a catch/vent tank system for my nitrous car with 12AN (3/4") fittings and lines.
Many 10AN systems are in use and very adequate up to a certain point of back pressure and oil travel through the system.
The larger line will reduce travel of oil and create a greater vented crank case for better ring seal.

 

thanks alot

 

could you go into further detail if possible on what you mean with "The larger line will reduce travel of oil and create a greater vented crank case for better ring seal" should i go 12an? im boosting with a 50 trim 48. a/r on 10-12psi hoping for 300+hp on a b18a1 fresh rebuild bottom ends gonna be mostly OEM besides all arp studs and bolts you can get, heads gonna have dual springs, ti retainers, bronze valve guides. OEM cams till later down the road

 

The larger line increases flow and reduces velocity. What you are venting is a gas, water, and oil mist mixture. The slower the air flow that is being vented the more time the oil has time to drop out to the hose walls before it reaches the catch can. If the velocity is too high in the lines then oil is carried to the catch can (even to the point of a little stream during WOT). Unless a recirculating can is used, that oil is now lost and removed from the system. You can offset some of this by adding more lines, but it is more cost effective and cuts out engine bay clutter by using a bigger line instead.

For your setup, two -10AN lines should suffice. If you feel the need, you can run larger lines with no ill affect.

 

-10AN is the industry standard. doesn't hurt to run larger, but isn't really necessary either...I see most 700+whp drag cars only running -10AN. one of our blown big block alcohol cars is running -12AN, but I've otherwise never ran bigger on small engines

not to say that what others are saying isn't sound advice, but I personally have seen no ill effects from running -10AN on anything under 1000whp

 

thanks for the help