lynchfourtwenty Posted January 16, 2009 Report Share Posted January 16, 2009 so i noticed something the other day i've never noticed before.. there was oil on my fire wall.. almost like the oil was bein spit out of the crank case vent tube.. i checked the valve cover an from what i can see its fine.. plus the oil is kinda low on the firewall, which is what makes me think the crank case vent tube.. while parked i revved the engine a little and i dont see any spitting out, but my friend said it did it while he was going up a hill, basicly the cab got a little smokier then usual (it gets smokey cause the exhaust is broken under the cab) anyway it got a bit smokier then usual an it smelled so he pulled over an check an thats what he saw, then he came here an made me look.. so i checked the oil an the level was fine, i just replaced it as a matter of fact.. i do remember reading something about an oil catch can some people put on those.. could this be why??? also it makes it look like my truck leaks oil cause it runs down the firewall onto the trans then onto the ground lol so any suggestions comments and or input is welcome and appriciated Quote Link to comment
DISLEXICDIME Posted January 16, 2009 Report Share Posted January 16, 2009 if you look at the bottom of your air cleaner for your webber is there a hole pop the plug out putt a 90 that fits in there and run a hose from the vent tube to the 90 and it will vent it back in to the carb Quote Link to comment
lynchfourtwenty Posted January 16, 2009 Author Report Share Posted January 16, 2009 the carb base plate? mine dont have a pre punched hole or whatever but i get what your sayin, Does anyone have the stock hose that runs from the breather?? would make things easier hehe.. also wouldnt oil spit up in there... would i just need to keep an eye on it an clean it? or maybe the angle of the hose an crap will stop oil from shootin out.. i been thinkni about doin that a while maybe i will check a junk yard if no one has a stock breather hose thing i can get... unless maybe i can use a regular hose but i'd be afraid of it burnin on the header.. Quote Link to comment
yello620 Posted January 16, 2009 Report Share Posted January 16, 2009 Those hose that goes to the air cleaner base, the other end of it goes to the valve cover. Its not anywhere near the header. Are you talking about the PCV hose? It runs under the manifold area and near your header. Do you still have a PCV valve hooked up? Quote Link to comment
lynchfourtwenty Posted January 16, 2009 Author Report Share Posted January 16, 2009 yea the thing on the block behind the header.. its a metal pipe that comes out an faces the firewall theres nothing at all hooked to it just an open pipe thats it Quote Link to comment
510er Posted January 16, 2009 Report Share Posted January 16, 2009 Its supposed to be hooked to the PCV valve, if its not hooked up you just have a wicked big vacuum leak Quote Link to comment
DISLEXICDIME Posted January 16, 2009 Report Share Posted January 16, 2009 oops my bad i am slow today for some reason i thought you where talking about the vent on the top of the valve cover my bad sorry josh. Quote Link to comment
lynchfourtwenty Posted January 16, 2009 Author Report Share Posted January 16, 2009 lmao no problem mikey, ok so what i need to get is the hose that goes from that tube thing get a pcv valve an connect it to the intake mani, i would need to drill an tap a hole in the plate thing that is on the manifold.. Quote Link to comment
copacetickid Posted January 16, 2009 Report Share Posted January 16, 2009 I don't know if that plate with the throttle cable mount is stock (i'm assuming it is), but no matter what year you have I think the PCV hose mounts up to it. Can't tell from the picture, but looks like it might have been plugged on yours? You will definitely want to find a one-way valve before you plug it into the manifold though, otherwise it defeats the purpose. When I bought my truck, it didn't even have the metal portion of the PCV hose on the block. When the engine was working, the blow-by went out the hole and straight into the cab vent, stinking up the cab like crazy. Also, there's a screen under the hole in the block (folded on itself 10 times like an accordion) that prevents any debris from falling inside the crankcase. It's hard to believe that oil in any quantity could make it up through that mesh... but that I don't know where else it could be coming from on that side of the engine. Unless it's really dirty brake fluid... Quote Link to comment
lynchfourtwenty Posted January 16, 2009 Author Report Share Posted January 16, 2009 yea its not brake fluid it'd notice some missing lol its oil for sure.. btw that plate on the intake mani is totaly custom.. came with the truck when i got it im thinkin if i take that plate off drill an tap a hole to put a pcv vavle in then i can hook a hose up to the breather thing Quote Link to comment
DISLEXICDIME Posted January 16, 2009 Report Share Posted January 16, 2009 There should be a nipple on the back side of the intake e hinde and kinde of under where you have your cable adjustment. here is how to do it page 26 in the 74 service manual http://www.olddatsuns.com//data/1974_Datsun_Pick-up_Serivce_Manual.pdf Quote Link to comment
Guest DatsuNoob Posted January 16, 2009 Report Share Posted January 16, 2009 (edited) PCV=Positive crankcase ventilation. Crankcase vapors blow from there back into the nipple on the intake to be re-burned, as I'm sure you know by now. I ran around for ages with an open PCV tube and a capped off intake nipple on an L20b with no bad results. I guess I just dont like the idea of anything but atomized fuel/air being burned in my engine, that's why I did it. Another thing you could do would be to run an oil catch can there if you wanted to, maybe figure out a way to recirculate any lost oil too? I suppose you could connect your PCV to the underside of the air cleaner plate as stated above, not sure if oil would ever travel that far up hill, but it's really supposed to be hooked up to the neck on the valve cover. Edited January 16, 2009 by DatsuNoob Quote Link to comment
hang_510 Posted January 16, 2009 Report Share Posted January 16, 2009 Its supposed to be hooked to the PCV valve, if its not hooked up you just have a wicked big vacuum leak :confused: PCV=Positive crankcase ventilation. Crankcase vapors blow from there back into the nipple on the intake to be re-burned... its still vented from the valve cover? then a catch can could help. you shouldnt be seeing much oil out of there, just vapors. a lot could indicate blow-by=rings. Quote Link to comment
510er Posted January 16, 2009 Report Share Posted January 16, 2009 okay are we talking about the same things here?!!! IN the above picture there is a hose coming off the valve cover that disapears behind the carb, when i brought the truck home that hose was venting into the bottom of the air filter. I also have a PCV valve below the carb which was wide open. The PCV valve In my understanding, is supposed to SUCK the excess vapors and recirculate them. IF you do not have a PCV valve then you dont have the the vacuum leak that i had. IMO if you dont have a PCV then dont put one in. If you want more pictures of my setup Ill wander outside and snap a few Quote Link to comment
hang_510 Posted January 16, 2009 Report Share Posted January 16, 2009 okay are we talking about the same things here?!!!The PCV valve In my understanding, is supposed to SUCK the excess vapors and recirculate them. its a passive, 1 way, device, allowing the crankcase gases to vent out enjoy... http://en.wikipedia.org/wiki/PCV_valve Quote Link to comment
510er Posted January 16, 2009 Report Share Posted January 16, 2009 Mine isnt passive, it sucks pretty good, ill take video of it later after my truck is warmed up. I dont see how it could be passive since it is attached to the intake which is sucking air...ill post pics tonight Quote Link to comment
Ketshy Posted January 16, 2009 Report Share Posted January 16, 2009 There was a thread about PCV valves not too long ago, I think the conclusion was that no, they are not passive and are beneficial to engine longevity though have no effect on performance. Running without that tube in place at least though can lead to some strong smells inside the cab, as has been said. Heres the other thread: What to do with my PCV Quote Link to comment
lynchfourtwenty Posted January 16, 2009 Author Report Share Posted January 16, 2009 There was a thread about PCV valves not too long ago, I think the conclusion was that no, they are not passive and are beneficial to engine longevity though have no effect on performance. Running without that tube in place at least though can lead to some strong smells inside the cab, as has been said. Heres the other thread: What to do with my PCV ok so what i've found out is the oil commin out of that thing is normal.. plus im not losing any power, but at the same time the engine maybe gettin a little dirty inside, so what im going to do is take that plate off my intake mani and drill a hole in it, tap it.. thread a thingy in there an run a pcv... but first im going to post in the wanted section for the hose that goes from the thing on the block to the intake Quote Link to comment
datzenmike Posted January 16, 2009 Report Share Posted January 16, 2009 The PCV valve is a very small metered orifice on the intake manifold. There is a spring loaded valve that is pulled open by engine vacuum and this allows air IN only. If the engine should backfire the pressure (or just the lack of vacuum) will close the valve so that engine fumes won't ignite and travel back inside the crank case. In operation, engine vacuum opens the valve and draws fumes from the crankcase. Fresh filtered air is drawn in through the valve cover vent from a hose connected to the air filter. Under hard acceleration, (low vacuum) or, if there is abnormal blow-by past the rings the crank case can be pressurized and the excess vapors reverse and flow out the valve cover vent and into the carb at the air filter. As you can see, at times, fumes are going to flow backwards out the valve cover vent, so connect it to the air filter. This way they will be sucked down into the carb and you won't have to smell them. During normal driving the PCV valve will collect them. Your car's system does not use a catch can so connect it up right, and forget about it. I hate when people fuck with things that work perfectly if left alone.... no not you Josh, I know it came like that. Quote Link to comment
lynchfourtwenty Posted January 16, 2009 Author Report Share Posted January 16, 2009 mike knows me well, im always tryin to better my truck... even if it means doing something i dont want to.. atleast the truck will be happy... i think whoever made this plate did a nice job, an i commend them for that.. but they shoulda done it right the first time... but just like everything else the P.O's did to this truck, i have to spend time an money to fix.. but its ok.. just another reason to refuse selling it, sometimes when people ask me to buy it i think about money, an how im soo broke an could use it.. but then im like... no way man cause they wouldnt appriciate all the stuff i've done to this truck, plus if i seen that they fucked it up some how i'd be pissed lol so when people offer me money, i just think about my hard work, an time, an its my baby :) but u know, it might have something to do with my step dad, when i was a kid he used to buy an sell cars alot, he had some really cool ones that i loved.. then he'd sell it.. so maybe thats what made me this way :P as i tell anyone i let drive my truck.... If you wreck it, its not replacable.. just cause theres more datsuns doesnt mean its easily replaced Quote Link to comment
DISLEXICDIME Posted January 16, 2009 Report Share Posted January 16, 2009 josh has a l16 manifold see if you can get it from him Quote Link to comment
lynchfourtwenty Posted January 17, 2009 Author Report Share Posted January 17, 2009 what about the smaller runners and such? wont it hurt performance? or somethin.. also i have a broken intake stud (oh boy im gonna hear it now) but theres no vacum leak i've checked! so if i replaced the mani i would more then likely have to get that broken stud out an all that... which i do plan on doin jus not right now.. i think i can get it out with plyers cause i dont think its broken off inside the head but not sure :( i forgot about that until just now.. Quote Link to comment
Guest DatsuNoob Posted January 20, 2009 Report Share Posted January 20, 2009 needledick vice grip pliers and some PB blastuurr and you should be in good shape... Hopefully.... (fingers crossed :D) Quote Link to comment
79datsun620 Posted January 20, 2009 Report Share Posted January 20, 2009 so what im going to do is take that plate off my intake mani and drill a hole in it, tap it.. thread a thingy in there an run a pcv... this is what i did when i get home ill put some pics of it.i got the fittings at home depot,1/4 pipe tread is real close to the treads on a pcv. Quote Link to comment
HRH Posted January 20, 2009 Report Share Posted January 20, 2009 On the PCV setup, the crankcase vent at the block should go up to the PCV valve in the manifold. The valve cover breather should go to the air cleaner with a felt filter in between the two. Factory air boxes have this breather filter. With a Weber, it's a bit more annoying, and it will tend to suck a little more than intended, which will crap up the carb fairly quickly. On the racecar I run the PCV hose correctly, then run an open breather on the valve cover. I think because it's running constant vacuum SU carbs it doesn't ever vent out the top, instead it pulls air through the motor from the top down. On the 620 with a lot of miles, I'm having issues with running the valve cover breather that way. It started puking oil down the firewall, which led me to put it back the way it's supposed to be, and I'm guessing a lot of blow-by because it's crapping up my Weber fairly nicely. Trying to figure out ways to remedy that. On the rebuilt 720 Z20s motor, however, I have it set up just like the racecar and have no problems of oil spewing out. Quote Link to comment
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