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Removing emissions controls on a 72

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So I was going over the timing and valve clearance adjustments for my 72 240, hoping this weekend to get some grease time in and make the engine run a bit smoother than it is (great shape, but currently needs a serious tune up). I noticed the wild variations in timing based on the presence of emission controls - a 12 degree difference?!! - and that, naturally, reminded me that since it's a 72, even in California it's quite alright for me to tune the engine for best performance and remove the emissions control equipment as I see fit.

The funny thing is, when I first got the car 5 years ago (my second Z after my first car, a 280, and my companion to my daily driver, a 92 300 2+2), it passed smog just fine.

Anyhow, I want to remove all of the emissions control equipment, but I'm not exactly sure what that entails. I know I'm supposed to remove the EGR valve and cap off both ends, but looking at the service manual, I'm pretty sure that's not all there is to it. Has anyone done this to their car recently, and would any of you who have feel like explaining to a newb like me what exactly is involved? Will I need to pull the engine, or can I do it all on the car? Any dangers involved? Once done, can I set the timing, idle, etc by the book for non-US emissions settings?

Any and all advice, help, etc, would be much much appreciated :-)

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There is a better way to handle the EGR on the balance tube. I have a '73 240Z, howbeit I have put an '81 L28 in her, rebulit with '70 SU carbs, etc. What I did was to obtain a '70 model balance tube from Z therapy, along with the carbs, of course. If you order it with the manifold it comes pre-assembled. Just bolt it onto your head (after, not before your exhaust) and your off to the races.

The '70 model balance tube is different the the one you and I had, no EGR to cap off, not to meantion the brake hose hooks on horizontally, not vertically. Make sure and hook up the PCV (or not, your call).

Another good idea here; if you don't have an original air filter box (the orange one), get it. It delivers air more evenly to each carb, and has factory air horns built in. It also pulls more COLD air than other filters do due to the enlongated shape.

As far as timing is concerned, do yourself a favor. Upgrade. I simply got an electronic distributor from the donor '81 280ZX, and its coil. Makes timing so much easier. No dwell to set. Ahhh! You need to rewire just a bit. I think I found the settings on the Datsun Z garage site:

(www.mindspring.com/~blittl/ZGarage.htm)

Alot of good advice here. Away I hope this helps....

------------------

"Go into emptiness, strike voids, bypass his defences; hit him where he does not expect you" -Lao Tzu

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Thanks for the tips :-) I think finding a donor ZX is in my future, given your praise of the ignition and the gear ratios from the NA 2 seaters (so I am told; bear in mind I'm a newbie to alot of this).

After spending a great deal of time staring at diagrams and the like, I just wanna make sure I have this right:

The EGR (referred to in the manual as the emissions control valve? I think?) regulates the amount of recirculated blowby gas from the crankcase ventilation system, correct? I'm not in a position to replace my intakes quite yet (not that I wouldn't like to), so I am still tryin' to make heads or tails of what I should change/modify/destroy. BTW, I do have the original air filter box :-) the car is just about as close to stock as you can get after 29 years of use.

So what I'm thinking is:

-Disconnect the smog pump - do I need to cap the piping? Or can I leave it rigged up as-is?

-Cap the crankcase vent outlet on the block and the matching end on the balance tube which serves the dirty air back up to the intakes. Is this the right way, or the wrong way?

-Leave the servo diapragm (which controls emissions during engine braking?) alone.

-Set the timing and idle rpm as per a non emissions controlled vehicle (17 degrees, 650rpm idle)

Sound right? Wrong?

Thanks again, and please forgive all the newbie questions.

[This message has been edited by Formica (edited 01-26-2001).]

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Similar questions... different pieces:

If I remove the smog pump circuit:

Hose coming from air cleaner

Pump

Hose to T fitting

Air galley

Backfire valve and fitting to balance tube

Is there something else I must think of/do? My understanding is that the pump blows fresh air into the exhaust system, which under normal running conditions just lowers the exhaust density, and the backfire valve senses a change in intake pressure and leans out the intake charge to prevent a hot rich mixture from becoming lean enough (and hot enough) to burn once entering the exhaust system. So, without the air injection, I shouldn't need to worry about the mixture in the exhaust manifold combusting right?

BTW--I'm using a 260 engine with SU carbs, electronic ignition, a higher output coil w/better spark wires, and aftermarket header. I ordered the header with smog fittings, since I had them with the stock header, but the fittings are proving to be too rusted to remove without destroying the air galley. Of course, these are discontinued, and necessary for the whole system.

I plan on leaving the crankcase breather system in place, since these hoses cause me no trouble, and theoretically help burn off extra gases without actually using anything more than air pressure.

In reality, the car pollutes as much without the air injection as with, correct? It's just a difference in pollutants in parts per million of the total exhaust gas which is just mixed with clean air to fool emissions?

Thanks in advance,

Chris

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It's just my opinion, throw all that Junk right into the nearest trash can.... Plug up the holes and readjust if necessary. your car will thank you with better reliability, and more HP. End of discussion.

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Re: Desmogging a 240z:  I’ve studied this carefully and consulted (real) experts for confirmation, and here’s what I’m going to do to my stock ‘72 240z:  Replace stock air filter with K&Ns,  Remove Air pump and connected hoses, remove check valve on air galley (on exhaust manifold) and plug with threaded hex bolt, remove anti-backfire valve (aka flame trap), cap connection to balance tube downstream from AB valve, plug vacuum leading from AB valve to balance tube, Connect orphaned vacuum tube coming from flow guide valve to the  closest carburator-to-air filter vacuum line using T connector.  Remove crankcase cover hose that went to stock air filter and replace with K&N valve cover air filter. Whew! 

Ive decided to retain the hose from crankcase to the balance tube/PCV valve.

Let me know your thoughts - very open to further coaching!  

I’ll post further if everything does NOT go well.  Otherwise,  assume this works!

Jughead

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2 hours ago, Jughead said:

Re: Desmogging a 240z:  I’ve studied this carefully and consulted (real) experts for confirmation, and here’s what I’m going to do to my stock ‘72 240z:  Replace stock air filter with K&Ns,  Remove Air pump and connected hoses, remove check valve on air galley (on exhaust manifold) and plug with threaded hex bolt, remove anti-backfire valve (aka flame trap), cap connection to balance tube downstream from AB valve, plug vacuum leading from AB valve to balance tube, Connect orphaned vacuum tube coming from flow guide valve to the  closest carburator-to-air filter vacuum line using T connector.  Remove crankcase cover hose that went to stock air filter and replace with K&N valve cover air filter. Whew! 

Ive decided to retain the hose from crankcase to the balance tube/PCV valve.

Let me know your thoughts - very open to further coaching!  

I’ll post further if everything does NOT go well.  Otherwise,  assume this works!

Jughead

As always - your car, your choices.  Consider this in electing to ditch the factory air filter box:

- you'll be giving up the factory designed air horns in the air filter box;

- as you've stated, you're also giving up the natural connections for the flow guide valve and the valve cover hose.

- the new valve cover filter will eventually saturate with oil vapor and drip onto the manifolds, then you have to add an unsightly catch can.

The factory air filter box may not look sexy but it does a darn good job of what it was designed for.  if you change your mind and keep it, block off the lower middle opening that connected to the air pump with a 1" rubber chair leg boot from a big box store.

Been there, done that.  Just my thoughts that you requested.

Jim

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4 hours ago, Jughead said:

 consulted (real) experts for confirmation, and here’s what I’m going to do to my stock ‘72 240z:  Replace stock air filter with K&Ns, 

If a real expert suggested you ditch the excellent stock air filter that brings in cooler denser air and replace with K&N filters that will now bring in hot air and a lot of fine sharp sand then maybe you should look for a more knowledgeable real expert. Yes K&N's are less restrictive but since the stock air filter has no problem supplying air in the first place, all you are really doing paying for something that will sand blast your upper engine.  My apologies,  K&N sand socks are a pet peeve of mine and I can never understand why they are so popular, good marketing I guess.

Oh, and welcome to the forum.

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Thanks!  And thanks much for the feedback - even if it wasn’t what I expected or wanted to hear.   Here’s what started his whole this:  I cant get the original air filter off with out the front wing nut getting blocked by the inner fender.  If I can figure this out, then based on what I’m reading her I’ll stick with the original.  Thanks again!  JH

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FYI... here's my set-up sans the emissions bits courtesy of Z Therapy.  Keeping the stock air filter box also lets you keep the carb overflow connections.  Note the boot covering the air pump connection behind the front carb - if you don't cover that opening, the carbs will be pulling completely unfiltered air and debris through it. 

L24-03 Small.jpg

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On 1/20/2001 at 1:56 AM, Formica said:

I noticed the wild variations in timing based on the presence of emission controls - a 12 degree difference?!! -

Did you actually measure and see this amount of variation or are you talking about the specifications in the FSM?

Timing can swing by up to 40 degrees or more with one throttle press, on an engine with common timing controls.  The emissions controls typically just affect idle timing.  Since you don't drive at idle it won't affect performance.

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IMG_0153.JPG

Update & follow up questions:  I've removed the air pump and its connected hoses.  I retained the factory air filter/housing and have have plugged where the air pump hose connects to the air filter housing.   I also kept the hose connecting the air filter housing to the rocker cover.  The engine still runs great. So far so good.

 So, now I'd like to clean up the orphaned air pump output connections.   Questions: 1). Can I remove the Check Valve and plug the hole without affecting anything?  2) Can I remove the Anti-Backfire valve and plug the hole with out aff Ching anything?  3). The anti-back fire valve hose connects to the  balance tube via a chrome tube with a slotted end.  (It's shown in the center of the photo just under the linkage diaphragm.)  Is this slotted chrome tube threaded into the balance tube?  What's the best way to remove it?  What type of screw should I plug it with (size, length, thread type.)?   Thanks!  Jughead

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On 5/9/2018 at 12:09 PM, Jughead said:

Thanks!  And thanks much for the feedback - even if it wasn’t what I expected or wanted to hear.   Here’s what started his whole this:  I cant get the original air filter off with out the front wing nut getting blocked by the inner fender.  If I can figure this out, then based on what I’m reading her I’ll stick with the original.  Thanks again!  JH

I used the 2 brown spacers (between the manifold and carburetors) from a 260 Z. They are thinner and allowed me to removed the stock air cleaner cover.

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1 hour ago, Powderkeg said:

I used the 2 brown spacers (between the manifold and carburetors) from a 260 Z. They are thinner and allowed me to removed the stock air cleaner cover.

@jalexquijano

 

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I did headers and deleted the EGR pump side of things. On my series 1 PCV and carb venting I went with the ITG filter and tapped both the valve cover with AN10 fittings and carburetor vents with regular fuel line to the back plate so they'd still flow as designed and kept the stock PCV setup which I think is a good thing. I used the MSA 50mm height velocity stacks which are fairly close to the stock air filter stack height. After the dealership drilled the big holes in my 1973 stock orange box to help with the vapor lock issue I figured this setup is very close to stock and also looks pretty darn good.

IMG_20180102_172826.jpg

 

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