Okay, I just ordered 2 valves from McMaster for my FI. I put one on the hose that goes from the drivers valve cover to the top of the intake, and I have an open K&N breather on the other valve cover. My question is- What is the line that goes from the back of the block to the front of the intake behind the throttle body? It looks like it has a solenoid controlling it on the intake and was just guesing this takes place of the PCV system, dont know. Should I put a valve on that line also? Or does that solenoid looking deal handle it by itself.

 

That is the evap solenoid for the gas tank I believe. You shouldn't need a check valve on that line.

 

you shouldnt need to add any check valves unless you have a vacume modulated tranny.

 

The PCV system that attaches to the intake manifold needs a check valve on it in some applications. The PCV valve will not stop pressure from getting into the crankcase without a check valve on the line.

Not all FI systems will need this, just depends on how the PCV system is configured.

 

My STS has a valve that operates off of a pressure switch. When there is over 1 lb of boost ( I think 1 lb but I have also heard 3 psi ) the switch opens the valve and vents the passenger side PCV line to the atmosphere. My truck has a fixed orifice in the PCV line on the driver's side which I assume lets boost into the crankcase which is then vented out through the passenger side PCV. Would a vacuum check valve be beneficial in the driver's side PCV line on my truck?

If the '04 is like the '03 the passenger side PCV line has no PCV valve in it. It runs from the front of the passenger side valve cover between the first and second injectors to a nipple on the intake manifold just aft of the throttle body. If you put a check valve in them both it will not get boost into the crankcase but will not be able to breath when you are under boost. I am not sure if this should be a concern or not.

 

Well,there is no pcv so i was getting full boost pressure in the crankcase. I have an open breather on the pass. side and it was pushing oil out that side. I didnt want to run the breather back to the intake the way ATI wants it, you would end up with oil in your intercooler. I put on a check valve and it has helped, I just didnt know what that other line was for. I figure a boosted crankcase has to cost some power also.