Valve cover hose question

[siteunseen]

I have an early '77 that has the hose from the valve cover attaching to the accordion boot before the throttle body. It takes forever to warm up. I notice a lot of those hoses going to the throttle body beside the one coming from the air regulator. I have the '78 FSM and it shows valve cover to throttle body. I guess I'll try it the newer way and see what happens. Just asking opinions. Thanks.

Edited September 16, 2012 by siteunseen
picture added

[Captain Obvious]

What's the question? What do you want an opinion about?

[siteunseen]

I was wondering if re-plumbing those hoses would do anything. It doesn't.

[Captain Obvious]

Haha! I'm really sorry... I still can't figure out what you're trying to accomplish, so I'm gonna shoot in the dark and hope I hit something valuable.

They changed some of the PCV and AAR air piping between 77 and 78.

In 77, it looked like this (sorry for the crappy pic). They pulled the air for both the upper PCV tube to the valve cover and the AAR off the same point on the throttle body. That point is just on the upstream (low vacuum) side of the throttle plate inside the throttle body:

In 78, they added a rubber nipple to the flex boot on the intake side of the throttle body and split up the air intakes for the PCV from the AAR. The PCV still got it's air from the same place as 77 (upstream of the throttle plate in the throttle body), but they moved the air intake for the AAR farther upstream to the new rubber nipple on the flex boot. The boot is missing from this pic, but at the very bottom of the pic you can see where the metal tube leading to the AAR would connect to it:

I've not got any real info on the reason they made that change, but I would speculate... On my 77, I get a lot of crud that comes out of the valve cover and through that upper PCV tube. I don't know if I've got too much blow by for the PCV to handle or what, but all I know is that it's dirty. So in my 77, I've got this dirty air stream coming off my valve cover, only to be sucked back through the AAR into my manifold. My AAR doesn't like the dirty air and gets really cruddy inside as a result.

So my speculation is that Datsun figured this out, and in 78 they changed the piping to split those two sources and moved the AAR intake farther upstream into cleaner air so it doesn't pull through all that crud coming off the valve cover.

None of this stuff will have anything to do with how long it takes your engine to warm up. If your AAR is dirty inside from breathing sticky oily residue from the valve cover, then it may take longer than it's supposed to for your AAR to close. Won't take the engine longer to warm up, but it may take longer than normal for the idle to drop.

So, like I said, shooting in the dark, but hoping I hit something!

[siteunseen]

Shooting in the dark is your best shooting! You nailed my plumbing questions, thank you. I'm pretty sure all the components I removed are the cause of the long warm up but the trade off was worth every minute I have to putt around until it heats up. Here's a picture of what I want to do but I think it may be counter productive if I understand you correctly. Take the cap (circled in yellow) and cap off the tube from the accordion boot then run my valve cover hose to where the cap was (in red) doing away with that section of hose (in green). Would that keep my throttle body from smudging up or make it worse? When I rebuilt and cleaned everything the throttle body was black and oily-smudgy. I apologize for my explanations, they're about as clear as mud.

[Captain Obvious]

Haha! Lucky shot! I had my eyes closed to boot!

Take the cap (circled in yellow) and cap off the tube from the accordion boot then run my valve cover hose to where the cap was (in red) doing away with that section of hose (in green).

If you do what you described above, then you will end up with exactly how Datsun did it in 77. The only difference would be the existence of the (unused) nipple on the accordion boot.

Would that fix your oily throttle body? I don't think so. Other than reducing the blow-by as much as possible (by engine overhaul work), I don't think there's anything you can do to get rid of it completely. You need to plumb that PCV vent tube to the atmospheric side of the throttle plate somewhere... There's just no way around it. Many newer vehicles run that line to the dirty side of the air cleaner, but because of the way the air metering is done with our L-Jet system, that's not an option for us.

However... Even though it wouldn't fix your oily throttle body, it would be simpler.

The plumbing scheme you've currently got I consider to be the worst of both worlds. You've got the extra plumbing for the 78, but because of the way you have things routed, you aren't getting the benefit of a clean air stream for your AAR. You've got the dirty valve cover tube still going upstream of the AAR and the throttle body. I'm thinking that you can make it simpler by doing what you proposed and going back to the 77 scheme. You won't see a cleaner throttle body, but at least it's simpler.

My thoughts on the 78 routing is they didn't do anything about oil in the throttle body, but at least they managed to clean up the AAR. Does that make sense? Do you understand the difference with routing in the 78 pic I posted?

in 78, Datsun has the valve cover piped to the throttle body and the AAR piped to the accordion nipple.

You have the valve cover piped to the accordion nipple and the AAR piped to the throttle body.

[siteunseen]

Thank you, thank you! I like a thinking man. I've just woken up so I can't wrap my mind around this just yet but I believe I understand what your saying. I'll re-read this when I get home from work.

On another subject, yesterday I bought an Accel super stock coil from Advance Auto online with a coupon code for $25.99, $28.33 w/taxes, it's smaller than the original but besides the hocus pocus they claim it really smoothed out my idle and seems to crank sooner which is now instant instead of before which took 2 cranks. Small details are progressing nicely. Thanks again.

[240260280z]

so in my 77, i've got this dirty air stream coming off my valve cover, only to be sucked back through the aar into my manifold. My aar doesn't like the dirty air and gets really cruddy inside as a result.

So my speculation is that datsun figured this out, and in 78 they changed the piping to split those two sources and moved the aar intake farther upstream into cleaner air so it doesn't pull through all that crud coming off the valve cover.

b i n g o !!!!

[siteunseen]

So I am going to make mine look like this picture. "I see" said the blind man. Thanks again.

[siteunseen]

I believe I got it now.

[280~Master]

My is routed this way. I have a 76 and no emissions either.

[Captain Obvious]

I believe I got it now.

Yup. You got it. You are now using the "78 scheme". Your throttle body will still be a mess, but your AAR will thank you.