O.K. I've asked what the pcv valve is for and got answers so maybe I should have asked what to do about my situation instead so here it is : I own a 91'Z that I transferred all my goodies into out of my 86' anyway I've completely done away with the computer (except for the speedo but anyway) and almost every other plug in it. I've put an older 350 that's .040 over and has 10:1 flat top pistons, an older set of double hump heads (the 375 horse if not mistaking, casting #492) that's been ported and polished along with my intake which is a performer RPM , it has a Insky cam with a 106 centerline, .510" lift, 280 duration @ .050, an HEI dist. with Accel super coil and module and Hedman headers along with enlarged pipe that goes to a flowmaster muffler as for a carb I'm open for suggestions (I've actually just got my car back together and am in the middle of stripping and painting it) anyway for now I'm using a holley that I'm not real fond of but it works o.k. but here's what I'm not sure on see my engine only pulls about 5-7 pounds of vaccum and I already have a canister for my pwr brakes, but do I have enough vaccum to operate my pcv valve I'm thinking it's kinda working but you have to rev it up and I would like to know what would be the best way to fix this problem, would a breather in the valve cover be alright (like the other side) or do I need vaccum pulling air out of my engine, my headers don't have the plug to adapt the plug and run the pcv to. So any ideas ????
well thanks and see ya later

 

At first, I assumed this was a typo and 280 was your total duration. But after readingI thought maybe it wasn't a typo! Seriously though, I'm going on the assumption that 280 is the total duration (probably in the 230 ballpark @ .050"). I'm guessing that either your carb is way out of whack (tuning) or you have a vacuum leak. If you're worried that your PCV valve isn't working under such low vacuum, don't remove the valve, fix the problem that is causing the low vacuum. I'm surprised that your engine will even idle without stalling.

 

One option would be crankcase evac. tubes, they say don't run them on street cars, but most of the guys here running these just unplugg the 1 side for street driving.

 

Well thanks for replying and your right it was a typo, it is 280 total duration and 230 at .050 but it still only pulls about 5-7 pounds of vaccum at an idle my carb's not brand new but it works alright. is that enough to work my pcv, do they make pcv valves that open at a lower vaccum pressure, would it be efficient enough. I don't want to hurt my engine its new and I plan on running it for a while don't want to rebuild it because something I forgot to do right. anyway thanks

 

First, it's "inches" of vacuum, not pounds.

PCV valves don't "open", they leak. They are there for two purposes: 1) orifice the amount of flow allowed into the intake tract (it doesn't take much); and 2) check flow in the case of backfire to prevent flames from entering the crankcase.

The spring that closes the valve in the check direction is so weak that very little vacuum is needed to allow it to "leak" in normal operation. I don't know the actual number, but I doubt it's causing you any problems.

 

Well thanks to all that replied and viewed especially those that replied, o.k. so I messed up and it's inches and not pounds opps! but at least ya know what I meant anyways so the 5-7 inches is enough vaccum to let my pcv work, and equalize the pressure or let my engine breath, I was under the understanding that it pulled air out of my engine to equalize the air as the piston travels or something like that but if everythings o.k. like it is then I'll probably leave it alone I just wanted to make certain that it couldn't cause premature wear or worse. thanks to all!!!
would like to hear from someone with similiar setup or vaccum and runs pcv and never had any problem or more suggestions
thanks.