Kynar check valve from US Plastics, reducing vacuum?

[Rock2610d]

So, at idle when I disconnect the PCV hose, motor acts like it has a huge vacuum leak. This is normal I know, but when I push on the Kynar check valve from US Plastics, with PCV still unhooked the motor runs a little better....less of a vacuum leak.

Is this us plastics check valve supposed to restrict some of the vacuum from pulling blow by out of the valve cover? I ask because it seems that more blow by is coming out of my VC vent with this check valve in place.

And yes it is installed right....pressure cannot go from intake to VC.

 

[DogWhistle]

Which model do you have? The largest one is 3/8", which should flow as much as the stock PCV line.

If your inside diameter is smaller, then yes, it may not be letting the manifold keep up.

 

[Rock2610d]

I have the 3/8" one.

There is a substantial difference in idle with the check valve installed but not hooked to pcv. Its restricting alot of vacuum.

Is this a bad thing?

 

[NHerron]

Good observation. You're correct, it's not flowing enough air to be effective at keeping crankcase under vacuum at idle. You might want to perform a leak down test and see if rings are shot. If you have link you could datalog what the crankcase sees throughout its rpm range, with a map sensor tapped in somewhere.

 

[Black95TSIawd]

Why do you have a check valve between the valve cover and intake pipe? The valve is supposed to allow vacuum to pull from the VC to the intake manifold and then block boost when there is positive pressure in the manifold.

 

[NHerron]

Who said valve was between vc and ic pipe? If that were true it wouldn't effect his idle.

He has it so pressure cannot enter vc. Pretty sure it's installed correctly.

 

[Rock2610d]

Why do you have a check valve between the valve cover and intake pipe? The valve is supposed to allow vacuum to pull from the VC to the intake manifold and then block boost when there is positive pressure in the manifold.

Its not between the VC and intake pipe. Its between the pcv valve and the intake manifold.

I do not think the rings are shot....its a fairly fresh rebuild with only 6 thousand miles on it. My last compression test showed 155 ish on all four cylinders....pretty good for 7000 feet of elevation. That is about equal to 185 psi in the low lands with my 9:1 pistons I think its spot on.

 

[crimsondragon]

You realize that the PCV is a check valve right?

 

[Black95TSIawd]

Its not between the VC and intake pipe. Its between the pcv valve and the intake manifold.

I do not think the rings are shot....its a fairly fresh rebuild with only 6 thousand miles on it. My last compression test showed 155 ish on all four cylinders....pretty good for 7000 feet of elevation. That is about equal to 185 psi in the low lands with my 9:1 pistons I think its spot on.

Why are you running the pcv valve and the check valve? Run a straight fitting on the VC. I'm sure having both is limiting vacuum flow some.

 

[Rock2610d]

I do realize the pcv is a check valve but my new one leaks above 10 psi. No leaks since I put this check valve in.

Putting a nipple on instead of pcv will not help....new krynar check valve reduces vacuum pull even when it is not hooked to pcv.

should i just take the krynar check valve off and live with the internal boost leak?

 

[okm12346]

Them valves crack after time. So what I do is to go to the junkyard and get brake booster hose from a 3g eclipse and use it instead of the PCV valve. Also, I've blocked the nipple where the stock PCV routes to, and I've drilled and tapped a spot on the high vacuum part of the IM (usually near the brake booster nipple). The vacuum at the stock PCV spot of the IM isnt enough to pull crank vapors, at least not whole alot of it

 

[crimsondragon]

I do realize the pcv is a check valve but my new one leaks above 10 psi. No leaks since I put this check valve in.

Putting a nipple on instead of pcv will not help....new krynar check valve reduces vacuum pull even when it is not hooked to pcv.

should i just take the krynar check valve off and live with the internal boost leak?

Is it an aftermarket PCV valve? I've heard issues with them. See if you can get an OEM one instead. P/N is MD024719. Check valves will restrict flow a little bit. Internally, vacuum has to pull the diaphragm open. Air will have to alter direction as well to flow around the diaphragm. There's really no way around it. If you're going to run the Krynar, replace the PCV with a nipple. It'll only cause a second restriction. If you're going to run an OEM PCV, you won't need the Krynar.

 

[NHerron]

Its been reported that OEM pcv leaks boost brand new. This mod is not new...

The objective is find a high flow check valve correct dimensions that will handle the heat and automotive fluids.

Some reading..
http://www.dsmtuners.com/forums/articles-engine-fuel/366890-4g63t-pcv-system.html