71Hustler Posted April 1, 2015 Report Share Posted April 1, 2015 Hi everyone, Quick question: As you can see in the photo, I have what appears to be an exhaust related hose just swinging in the wind. I'm thinking this isn't normal, but I'm pretty unclear where it should be going instead. 1 Quote Link to comment
67_1600 Posted April 1, 2015 Report Share Posted April 1, 2015 Maybe here? It looks like it's been blocked off with a large bolt or something. 1 Quote Link to comment
datzenmike Posted April 1, 2015 Report Share Posted April 1, 2015 You don't have any exhaust related hoses. The large curved black hose should be connected to the red-ish one with the gear clamp and large bolt in it. This is the block vent to the PCV valve on the intake. That's an L20B engine BTW. The other two much smaller blocked hoses are vacuum supplies. 1 Quote Link to comment
71Hustler Posted April 1, 2015 Author Report Share Posted April 1, 2015 Holy crap! You're right DatzenMike! This explains why I couldn't make good sense of the diagrams in my Haynes manual. 1 Quote Link to comment
71Hustler Posted April 1, 2015 Author Report Share Posted April 1, 2015 Ok, thanks for the responses! Seems like I should reconnect these, but still confused as to why they would have ended up this way. At least now I know what engine I'm working with--I just blindly assumed an L16. 1 Quote Link to comment
uberkevin Posted April 1, 2015 Report Share Posted April 1, 2015 521's never came with an l20b so not to crazy to think a 16 would be in there. Let's see some more pictures! 1 Quote Link to comment
datzenmike Posted April 1, 2015 Report Share Posted April 1, 2015 Ok, thanks for the responses! Seems like I should reconnect these, but still confused as to why they would have ended up this way. At least now I know what engine I'm working with--I just blindly assumed an L16. The hose is larger on one end and smaller on the other so hard to replace. Do your best. L16 also had a block vent tube but it isn't like the one you have, it sticks straight out from the block. 1 Quote Link to comment
71Hustler Posted April 1, 2015 Author Report Share Posted April 1, 2015 Knowing what to call it now definitely helps. Datzenmike, on a different thread that came up on a search for block vent tube (http://community.ratsun.net/topic/40557-lower-crankcase-breather/) you said: It won't blow a seal unless the hose on top of the valve cover is plugged. This vent is there for a reason. It's part of the PCV system but it's biggest value is to ventilate the block fumes which will extend the oil change intervals by removing water vapors that will condense and mix with the oil. Who ever did this was terribly misguided. Blocking this off serves no good purpose and in the long run is damaging to the engine.. This applies here too, correct? So, I likely have this situation simply because it's hard to replace. There's no functional/preference reason someone would disconnect these, right? 1 Quote Link to comment
datzenmike Posted April 1, 2015 Report Share Posted April 1, 2015 The PCV valve uses a tiny amount of intake vacuum to 'gently' draw damp air and fumes out of the crankcase. As air is sucked out fresh dry clean air from the air filter is allowd in through the valve cover hose to replace it. These fumes would normally condense overnight and contaminate the oil so this simple thing keeps the engine insides cleaner and extens the oil life and changes. The PCV system is absolutely benign in opperation even if the hose were to fall off. There is absolutely no good reason for not having it working. 1 Quote Link to comment
ggzilla Posted April 1, 2015 Report Share Posted April 1, 2015 There's no functional/preference reason someone would disconnect these, right? One functional reason: some racing programs require on oil catch can, so the PCV is replaced with that. Preference for some, I have heard these reasons: * "it looks better without the hose" * "it was easier to leave it plugged, and it seems to run OK" * "it is emissions control, so it must be bad" * "I've heard theories that it hurts performance, that the air dilutes the mixture" * "race cars don't use them, so it must hurt performance" 1 Quote Link to comment
datzenmike Posted April 2, 2015 Report Share Posted April 2, 2015 At full throttle intake vacuum is extremely low so even less air is drawn in than at idle. WAY less. Idle mixture is calibrated at the factory to include this tiny 'leak'. Besides, there is a mixture screw for setting the idle mixture. A catch can is a ridiculous thing to put on a street car. It's the ultimate "Hey I have a catch can, so I have a race car". You can substitute the following things for catch can... Drilled rotors Strut brace rear spoiler engine torque strap blue valve cover air filter dual oil filters cone air filters ..... 1 Quote Link to comment
71Hustler Posted April 7, 2015 Author Report Share Posted April 7, 2015 Would this blowby hose from a 1980 720 L20b work (#11828)? I don't know what year my engine is or if there were variations of the L20b at all over the years...? http://www.nissanpartsdeal.com/Page_Product/PartDetail.aspx?Vin=&Make=Nissan&Model=720+Pickup&Year=1980&Submodel=&ModelSeries=720&FileType=236&SelectConditions=%28%29&ProductionDate=&PaintCode=&TrimCode=&Left=&SectionNo=A&ComponentsNo=118&PageName=118_M01 Quote Link to comment
datzenmike Posted April 8, 2015 Report Share Posted April 8, 2015 Yes, 11828 should be close enough to work. 1 Quote Link to comment
71Hustler Posted April 21, 2015 Author Report Share Posted April 21, 2015 New PCV valve and hose re-installed! Now moving on to other mysteries. 1 Quote Link to comment
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.
Note: Your post will require moderator approval before it will be visible.