Air Cleaner Housing / Vacuum Lines

[mx71]

I know there's a bunch of info on vacuum line routing, but I'm not sure if these are vacuum lines. I've had the factory carb put back on the truck, and the air cleaner assembly the shop put on has been cut and is ugly. I had gotten one on ebay from a similarly equipped 85 KC 4x4, and it has the two hoses going to the front of the assembly. The one from the shop doesn't have those two bigger hoses, and I know there are some that exist that have only one hose. After some googling and searching on here, I can't figure out what it's for or if it needs to be hooked up. It has some sort of reed inside of it.

 

[Lockleaf]

Those are the passages for the auxiliary air injection for the exhaust. If your exhaust manifold doesn't have those pipes just ignore them.

[datzenmike]

 

The Z series engines in the 720 did not use an air pump. So who ever told you that is wrong.
 
Instead one, or in the case of the 4x4s, two pipes were run from the exhaust manifold to the air filter. At the air filter end are one way reed valves. Each exhaust pressure wave is followed by vacuum wave. The vacuum waves are used to suck in air through the reed valves which prevent reversal of flow. The oxygen rich exhaust is then fed through the catalytic converter and 'burned'.

 

 

Already explained about one or two hoses and how it works. ALL 720 gas engines had this.

 

 

 

 

 And you need the air filter with the pipe down to the exhaust manifold

 

 

Look on your exhaust manifold for a fitting. Usually one pipe for 2wd and two for 4x4. Her's my single pipe on the right. There would be another pipe connecting it to the air filter.

 

 

 

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[mx71]

I have a little clamp that the 02 sensor wire is resting in. That must be where that pipe is supposed to go. Mine is a 4x4. I guess I’ll have to track down those pipes now.

[mx71]

Well, my truck must be an anomaly or have an aftermarket or other exhaust manifold, as it doesn't have any ports. It's an 85 KC 4x4 Deluxe.

 

[wayno]

There is more than one version, I have never seen your version with the exhaust being pumped into the air filter in a 720, but I have not been looking, I have the one I am scrapping where it is pumped into the intake manifold.

I do have an A series made like yours.

[mx71]

Well, this isn't the one that came on the truck. I got it on eBay. The truck came with an old Motorcraft carb which I recently replaced with the factory one. I imagine this might have come with the air filter housing with no exhaust tubes coming out of it. My 82 I had in high school had 1 or 2 tubes coming out of it, but it was a California model.

[datzenmike]

wayno, no exhaust goes to the air filter. After every exhaust pulse there is a strong vacuum wave. These pulses travel up the pipe to the air filter where there is a reed valve that only opens to the vacuum wave. This sucks in a very small amount of air. Sop pressure waves blocked but vacuum waves allowed. A series od puffs of filtered air is sucked down the pipe and into the exhaust to add oxygen so the Cat can burn the left over hydrocarbons in the exhaust.

 

The exhaust into the intake is the EGR and you can see that pipe to the left of the dip stick handle going around the back of the head. A varying amount of oxygen depleted exhaust is added at part throttle to dilute ans calm the combustion chamber temperatures that cause NO_x. There is no EGR at idle or full throttle so it has no effect on performance.

[wayno]

So does the line going around the back of the head lead to this valve that goes into the intake manifold, it has an orange hose on the valve.

If so you should PM me as I have an 86 that has the air filter housing you likely want.

 

wayno, no exhaust goes to the air filter. After every exhaust pulse there is a strong vacuum wave. These pulses travel up the pipe to the air filter where there is a reed valve that only opens to the vacuum wave. This sucks in a very small amount of air. Sop pressure waves blocked but vacuum waves allowed. A series od puffs of filtered air is sucked down the pipe and into the exhaust to add oxygen so the Cat can burn the left over hydrocarbons in the exhaust.

 

The exhaust into the intake is the EGR and you can see that pipe to the left of the dip stick handle going around the back of the head. A varying amount of oxygen depleted exhaust is added at part throttle to dilute ans calm the combustion chamber temperatures that cause NO_x. There is no EGR at idle or full throttle so it has no effect on performance.

My A series engine has both them rather large pipes coming off the exhaust manifold going straight to the air filter housing, it may suck air in though.

[mx71]

Well, I originally got this truck for 1000 dollars to teach my wife how to drive a stick. I'm now in it for $3,000, so I'm trying to limit any other money I spend on it, unless you're talking about a trade.

[wayno]

Well, I originally got this truck for 1000 dollars to teach my wife how to drive a stick. I'm now in it for $3,000, so I'm trying to limit any other money I spend on it, unless you're talking about a trade.

 

As I said, PM me and we can figure out if I have what you need.

[mx71]

I found a write up of vacuum line routing on the NICO forums, but it's a little unclear at times, and I think different from my federal 85 z24 4x4 high altitude. I found these on nissan parts deal and they were very helpful.

 

https://www.nissanpartsdeal.com/parts-list/1985-nissan-720-pickup/engine-control-vacuum-piping.html?Diagram=223_T01

[nismo24096]

I am in the process of moving, and came across my stock air cleaner and factory carb from my 1982 720, if you want it I will be willing to pretty much let you have it, but you have to pay for shipping, I have long since sold my truck, and still kicking myself for doing so..but oh well. would love to help out the community.

https://www.dropbox.com/s/zf9nenmvqghmg6m/20171123_204842.jpg?dl=0

[mx71]

I ended up getting a housing on eBay and a new carb, but thank you!