Under hood help (260z)

[Dlobi]

Cleaning up under hood. Trying to keep as complete and stock as possible. What goes in these two places? Clip along top of air cleaner top and a little port off the back of the air cleaner box. I'm guessing the holes along the top of the air cleaner cover do not belong there. 

[RS02]

I think the holes on top was not supposed to be there. And the little barb might be for the fuel vapor line which should be on the driver side wheel well. I'm not sure. I have a 240z...


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[beermanpete]

The "little port" is for a hose that goes to the throttle opener. The clip is shown in the fuel system section with a hose but the copy I have is not clear enough to determine which hose it is. The holes along the top look factory to me. Check the edges of the holes for paint. If these are factory holes they will be painted. A mod by a previous owner may not be painted or it might not match the original color correctly.

[Captain Obvious]

The holes are stock.

The clip on the top of the air cleaner is meant to hold a vacuum tube that wraps around the front snout air intake and actuates the thermostatic temperature controlled air flappy thingy. The one that pulls air from the exhaust manifold until it warms up.

And as mentioned above, the small hose nipple connects a tube to the throttle opener control valve. It's the clean atmospheric source to disable the system when the speed is below 10 mph. It should connect to the solenoid valve here:

[Dlobi]

Wow. Nice captain. Thank you. I'll go look in the morning. Also thanks to beermanpete. The holes are perfectly spaced and in line. Factory paint in the edges. Must just let it breathe a little more. They look silly. Should have enlarged the snorkel bit that would have cost more. Just keep making em and add holes I guess. 

[Captain Obvious]

Glad to help continue the existence of a set of flat tops.

So I got a question... That nipple on the back of the air cleaner is supposed to go over to the throttle opener solenoid, but you've already got a vacuum tube connected to the solenoid. Looks like it's leading up to the front carb somewhere? What's that hose connected to?

And my read on the little holes on the air cleaner goes like this: When the incoming air is warm the ATC control valve on the snout brings in air direct from the snout opening. But when the incoming air is cold, it changes the valve and pulls in air heated from the exhaust manifold. But even when the valve is set to the exhaust manifold intake position, you'll still always mix in a little bit of cool fresh air from those little holes.

[Dlobi]

The hose we are speaking of on mine is currently attracted to one of the two additional ports lower (about mid way) on the back of the air cleaner. Could move it up I suppose but that would simply leave another spot without a hose attached. This airbox does not have the (earlier?) Manual winter/summer flap on the snorkel. The heated air tube is missing but this car will never be driven in cold weather (at least by me) anyway. Somewhere I must have an open port for that last hose unless one of the ones on the air box was simply plugged off. 

 

Riddle me this thought about the snorkel and new holes on the 260 air intake.. Remember, the 2.6 liter displacement was to compensate for the lowered compression (emissions I think) from the 240s 2.4 liter displacement. This was done with the same block by just lengthening the stroke. We now need a little more air delivered to fill a slightly larger chamber. The snorkel size seems unchanged so possibly the holes would make up the difference. 

[Captain Obvious]

I don't think there was ever a manual summer/winter flat top air cleaner. The FSM makes a big deal about the ATC (Automatic Temperature Control) air cleaner. They got rid of the manual summer/winter valve and used the new fangled automatic one instead. One of the many, many Z design items  that marked the steady slide of "automatic" and "convenience" from 72 until 96. You know... As the weight went up.

If you've still got a nipple unconnected, I can take a pic here if that would help. I (think) still have a 74 air cleaner around here somewhere and can take a pic of the back and label all the connections.

And about the snorkel... There's no way that snorkel is the limiting factor on the amount of air getting to the engine. Those little holes surely can't matter for the 200 cc displacement change between 2400 and 2600. I wasn't there when they designed it, but I just don't see it. 

[w3wilkes]

Those holes on the air cleaner housing were added by the dealer on my 73 240Z on one of my many trips to the dealer in attempting to correct the vapor locking problem. I wasn't aware that it became a factory standard for the 74 260Z. I notice in the pictures that the fuel lines are all wrapped. That was also done by the dealer on my 73 240Z for the same vapor locking issue. These and the dealer adding an electric fuel pump were all done attempting to correct the vapor locking issue. The vapor locking never did get completely corrected, I can remember many times pulling the hood release in hot summer days to get a little extra under hood venting when the temp gauge would start climbing and the motor would start to stumble.

[Dlobi]

Good stuff w3,

I'm not positive but others will likely know with more authority.. I'm pretty sure all the zip ties and insulation on my 260 fuel lines was factory by 1974. Pretty sure an electric fuel pump at the tank was also standard. Not sure about either however. I wonder if the vented hoods on the 280s were for the same reason. My first ever car was a 72 240, 37 years ago, now that mention it, I vaguely recall having vapor lock issues in the summer. 

[ensys]

 

From an observational standpoint, it would seem not uncommon for the Z engine room to be a pretty hot place now and then.

 

Mine accrued nearly all its 200K mi. in No.Cal. w/trips in surrounding states, and I can only remember a couple instances of overheating, which could easily be a matter of dumb luck rather than indicative experience. I will note one thing that may or may not matter: I removed the bottom shield early on, indicating a greater concern for air flow than aero efficiency.

 

I confess that I've never quite understood why this condition exists in the Z. Its got a good fan, and shrouding, tho I suppose the radiator could be more robust. And of course, having the A/C condenser sit in front of it doesn't help things. On the 280, I'm sure it doesn't help to have the hood vent above the "hot side" largely blocked by a clumsy rain tray.

 

But I've known a few one-side-in-and-out engines in tighter confines that never had these kind of heat soak problems.

Very curious. And annoying.

 

Edited November 4, 2017 by ensys

[Zed Head]

Nissan actually define it better than just "vapor lock" or "heat soak".  They wrote a thing about it.