Can someone tell me if this will do any harm

[Guest bastaad525]

I mentioned briefly in another thread, that when I got the head rebuilt and put it back on, I swapped from the stock turbo intake manifold, to a '75 280z manifold. It worked out great, except that the placement of the PCV valve on the '75 made it necessary to remove it and weld up the hole. Now I know a few guys who just run the crank and valve cover vents both open to atmosphere, so I figured it wouldnt' be a problem to do this. Well, though it didn't affect the way the motor ran, it did cause one significant problem... extremely bad smell in the cabin, whether the windows were open or closed Enough to make me light headed and my eyes water. For now, I dont have a way to get hole put into the intake manifold to put a PCV valve back in, so I'm kinda stuck. I tried something out but wanted to check with you guys and see if this could create any potential problems. I capped off the crank vent completely, and then ran a hose from valve cover vent back into the boot between the turbo and the AFM. Now as far as I can figure, this would not create any vacuum leaks or unmetered air to enter the system, as the only two places the engine should be able to draw air in from are the crank and valve cover vents, right? (ohhhhhhhh dammit and the oil dipstick.... forgot about that one. I'm gonna have to check that one and make sure it's sealing really well). Also, since there only ever constant suction in the boot (unless I get a backfire thru the intake I guess) air should never be forced back into the valve cover so it shouldn't pressurize. And this way any dirty air from blowby or whatever will still be sucked into the intake and burned off, right? At any rate one thing I did pay close attention to was the idle, and routing the hose like this did not change the idle AT ALL so I'm 99% sure I did not create any vacuum leaks. All I DO know for sure is that it definately made a huge difference and now if I drive with the windows up there is NO smell in the car whatsoever...

 

windows down is another story I dont understand why I get such bad exhaust smell in the car, the exhaust is all new so shouldn't have any leaks, and I've recently replaced the rear hatch seal and tail light seals... dont know where it's getting in from unless from the windows themselves? And why is it so much worse when it's cold?

 

So please please please tell me that routing the vents like this will not cause me any problems??

[Guest bastaad525]

No one has any ideas on this? I dont want to screw anything up by running the car this way

[SleeperZ]

You aren't hurting anything, but you may puke some oil into your intake if you get a good amount of blowby. This can happen anyway with the PCV system intact, but it's harder for oil to find it's way from the crankcase breather. Why not put a filter on it instead of capping it?

[Guest bastaad525]

I had left both the crankcase breather and the valve cover breather open with filters on them, after we put the '75 manifold on there, but there was just a ton of smell getting into the car... much worse than its ever been, even with the windows up. I mean eyes watering bad. It didnt used to be that bad when the PCV system was all hooked up the way it was supposed to be, so I figured the odor had to be coming from the open breathers. Sure enough, when I capped the crank breather and ran a hose from the valve cover breather back into the intake, the smell was cut down a lot, completely gone with the windows rolled up, still getting some bad exhaust smell in the car with the windows down though... I have a thread about this in the Misc. Tech section here:

 

http://hybridz.org/phpBB2/viewtopic.php?t=25746

 

Sleeper - wasnt it you that told me that if I left one of them open and the other routed to the intake that it would create a vacuum leak? I figured if I just left the crank breather open, but rerouted the valve cover breather to the intake, that it would just suck extra unmetered air from the block thru the head and into the intake, so I capped it. I actually want to just route both of them into the intake so they can just circulate similar to how they would if the PCV was in place, and will most likely do this tommorow. Anyways I'm glad I'm not damaging anything and my lungs dont have to suffer as much!

[SleeperZ]

Tha vacuum leak happens when you don't seal the PCV valve on the bottom of the manifold. I believe you said you capped it and ran the valve cover to the intake. Once the PCV system is disabled, and the intake is sealed so all the air passes through the AFM, you can open your crank case/valve cover to the world with no consequences for your air metering.

[Guest bastaad525]

ah that's where the misunderstanding lies I routed the valve cover breather into the boot AFTER the AFM, before the turbo (I used that because there was already a port there that I could hook the hose to), so if it were to suck in air thru an open block breather it would be unmetered. But I figure with the block capped off and the oil dipstick sealing well (verified this yesterday, it's sealing very well and the idle changes when I remove it) then the intake cant suck air in from the valve breather, but if there is any blowby it will suck that up w/o affecting the mixture (I hope??). I noted the idle when both breathers were open to atmosphere, and then when I capped the one and hooked up the other to the intake, and it did not change at all afterwards so I"m assuming there's no unmetered air getting in. I've actually been considering routing both the valve and crank breathers to the boot right in front of the AFM, instead of after it, I'll have to cut holes into the boot and then seal them against the hoses. I know this would be the best, safest way to do it.