superduner Posted August 7, 2012 Share Posted August 7, 2012 Hey team just curious as to whether or not on an engine swap to an s30 where smog is not required, whether or not the pvc valve could be blocked off? I did a boost leak test on my L28et with FMIC and the only place i noticed i was loosing pressure was air going into j hose that went from the pcv valve to the crank case tube. is this supposed to be normal (leaking) ? if not, would there be any performance consequences with the removal or blocking off of it? Just wondering what others have done in regards to addressing this? Quote Link to comment Share on other sites More sharing options...
letitsnow Posted August 7, 2012 Share Posted August 7, 2012 PCV is a good thing, leave it and get a better check valve. It helps prevent oil leaks and keeps the engine bay cleaner. Quote Link to comment Share on other sites More sharing options...
Gollum Posted August 7, 2012 Share Posted August 7, 2012 Plenty of people bypass the PCV system, though I must add the obligatory legality warning. Just because your car is "testing exempt" does NOT make it "smog law exempt". You're still "required" to take an engine swapped vehicle to the smog ref to get a BAR label, and you're required to keep all the smog equipment from the donor vehicle. Now, what you want to try to get away with is up to you, and I think you have a clue as to what other people get away with. But I won't openly condone blatant ignorance to law information that's widely available to those who look. So now you're at least informed on the most basic of levels. With that out of the way, feel free to plug the whole system up, and add a breather to the valve cover so that the engine can still breathe. If you totally seal up the PCV system top to bottom then you'll end up blowing seals. There's a good reason old Ford Model A's, T's and more leaked good amounts of oil. They simply HAD to leak by design because if the seals kept oil out they'd end up putting undo stress on other parts. Companies at the time realized that there was increased pressure in the crankcase when running and their simple solution was to run seals that didn't quite "completely" seal. I guess they thought that since air was a gas and not a fluid they could get by with enough air flow with minimal fluid leakage. Later engineers designed crankcases to breath internally much better and then added openings with filters to catch oil and then tightened up seal tolerances to keep more oil inside the engine. But let it be noted, that when PCV systems were added in the 60's the research at the time showed that roughly HALF of the HC emissions coming from an engine was right out of the engine breathers. I haven't seen modern research that refutes those claims, and considering how much cleaner a modern engine burns I'd imagine the potential HC output from the crankcase could be a much higher percentage today. Also pay attention to the OTHER benefits of a PCV valve that make it not exactly "just a smog device". With PCV valves introduced oil lifespan quality improved dramatically helping engines to last longer. The overall internal condition of the engine just stays much cleaner, which might be worth diagnosing your issue with the PCV system. To people that choose not to run PCV valves I recommend you change your oil RELIGIOUSLY and if you're going to be racing on the motor, I'd even change it VERY often (which should be a given anyways honestly). Quote Link to comment Share on other sites More sharing options...
Zmanco Posted August 7, 2012 Share Posted August 7, 2012 Keep in mind how much air is flowing through the intake manifold vs. how much will leak through the valve when it's sealing properly. I can't see any good reason to remove it. I'll also add to Gollum's summary of good things that come from a properly configured PCV system: if you run the engine hard for long periods, such as on the track, you'll want to route the breather through a separator/catch can. Without one, expect to clean the engine and underside of the hood regularly. Quote Link to comment Share on other sites More sharing options...
superduner Posted August 7, 2012 Author Share Posted August 7, 2012 (edited) Thanks Gollum for the legal advice, well noted. And makes perfect sense that pressure would blow seals however now that the question of whether or not to remove the valve has been answered, the questions of *whether or not on an L28ET should the pcv valve be allowing air to leak into the crank case breather tube when conducting a boost leak test*, remains. example. I hook my custom(home made) took to inject air from a compressor into the turbine and fill the intake system until 10PSI has been reached on the pressure gauge. then i listen for the hissing of air leaks, and the only leak heard is the hissing of the air going into the crank case via the j tube from the pcv valve. Normal? P.s gauge looses psi rather slowly, but a loss of pressure remains none the less Edited August 7, 2012 by superduner Quote Link to comment Share on other sites More sharing options...
Gollum Posted August 8, 2012 Share Posted August 8, 2012 I'd imagine there shouldn't be any reason for it to leak under boost. The good news is that autozone has them for $2.99 which sounds like a fairly cheap experiment to me. If there isn't an autozone nearby, oreilly has them for under $5 as well. I'd just go pick up a new one to try out for that kind of outlay. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted August 8, 2012 Share Posted August 8, 2012 I bought a new one and it leaked too, but it was just a small hiss, doesn't bother me that much. I am tempted to try one of the slash cut exhaust pcv things for the other vent though. Quote Link to comment Share on other sites More sharing options...
superduner Posted August 8, 2012 Author Share Posted August 8, 2012 Yeah exactly it wasn't a big leak but it still leaked. And well, from what I had heard you didn't want ANY leaks on turtle cars haha. So just decided to post about it and confirm if this was normal. Il definitely buy a new one if they're that cheap just to be on the safe side Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 8, 2012 Share Posted August 8, 2012 Why do the big boys in NHRA run Vacuum Pumps on the Crank Case? Find the answer, and you will answer your own question about the PCV. It's not just an emissions component. They're cheap, and the Nissan Valve is more than just a check valve. It is a flow-control device. It throttles the amount of evacuation given dependent on load and engine speed. The OEM design has at a minimum 4" W.C. evacuation pressure on the crankcase AT ALL TIMES if not slightly more (midrange)... Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted August 9, 2012 Share Posted August 9, 2012 You won't believe how many dealership technicians have never replaced a PCV valve. In the early 90s, my team leader had a few hundred in his "bolts drawer" of his tool box so I got most of them. 20 years later, I still haven't gone through all of them and I spent many years putting them into any car that had a running problem at the dealership to eliminate one possible issue and make my job easier. Just yesterday, I put one in my M30 because the old one was a year old. Tony is right.....PCV is important and a functioning pcv system will ensure your oil doesn't age prematurely and lose it's desirable properties. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.