In depth procedure for removing AIR pumps and related vacuum tubing

[Rickf1985]

Kevin is talking about the pipes that go into the exhaust manifolds.

[davecaprita]

We had this same issue with our 87.  In "AIR / SMOG Pump System Failure" in the Chassis-Chevy section I posted some pics about the plugs with the unique thread arrangement.  I tried the plumbing section also but didn't find anything remotely close to the NPT fine threads setup on our rig so I had some machined just for the purpose of plugging the A.I.R inlets.

[legomybago]

I believe the thread size for those plugs is 7/8x18 W% Your not going to find them a Lowes...The factory did that so people wouldnt just pull these systems off and run down to there local hardware store and buy pipe plugs. I've read that oil pan drain plugs are the same thread?? Expensive though

[cncsparky]

A quick search I found Doorman # 65231 drain plug is 7/8-18 and found some peeps using them for exhaust manifold plugs.  Get them at rock auto for about $2 ea. 

[legomybago]

Nice cncsparky

[Rickf1985]

Yours must be a LOT bigger than mine! A 7/8 pipe plug is a BIG plug. I have mine up in the air now and am ready to do that part of it so I will look into that today. Maybe I am just not looking at it right, it is kind of hard to see.

[DonD]

For a 1994 â€" early 1995 with stock exhaust manifolds, and you delete the AIR pump system, you will need a â...ž-18 drain plug. Dorman P/N #65231, UPC #74956523159

For a late 1995 â€" 1996 with stock exhaust manifolds, and you delete the AIR pump system, you will need a ¾-16 drain plug. Dorman P/N #65226, UPC #37495652261.
Impala SS Forum.

[Rickf1985]

I have an 89
And the Impala SS used a LT-1 did it not? May be a bit different?

[ClydesdaleKevin]

So...what size would they be for an 89?  Not too many 90s coaches here...lol!

Kev

[Rickf1985]

I was under there yesterday putting the charcoal canister back up and hooking the lines up. Flies bitting, 98 degrees out. I was NOT going to get into the exhaust at that point! N:(

[DonD]

Kev, These should fit. Some guys use exhaust sealant for thread lock.

http://frugalmechanic.com/auto-part/dorman-65231-engine-oil-drain-plug

[Lefty]

If you are referring to the holes in the exhaust manifold, I can assist you.

Look here:  http://www.napaecatalog.com/app.asp?RelId=5.5.13.9&Archival=1&BookCode=ebp13flx

When the catalog comes up, enter page 42 in the page box at the top and hit <Enter>

Look about 3/4 down the page and you'll see "45deg. Inverted Flare Plug"  The Weatherhead (Eaton) part number should be either # 39-8 or # 39-6 depending on if it's a 1/2" or 3/8" hole.

[TripleJ]

FWIW, I removed the air pump while I had the radiator out.  The fittings on my exhaust manifolds were corroded almost to nubs.  There was no way I was going to get those lines to come out intact.  I ended up sawing the metal lines off flush-ish with what was left of the fitting and using an 8mm-1.25 tap until I was comfortable with how many threads I had, then running some bolts into the holes.

Yeah, theyre not even looking, but they tightened up and theres no leaks...

[Old Toolmaker]

For what it's worth (FWIW) on our '86 454 the A.I.R. ports in the exhaust manifold are 22mm X 1.5mm and I used oil drain plugs.

[pvoth1111]

Exhaust manifold....part of the EGR system.

[Rickf1985]

Which has also been disabled. :)rotflmao

[Old Toolmaker]

I had two problems, a lean surge and an exhaust leak that turned into 8 exhaust leaks.  The EGR was the first to go simply to eliminate that as a cause of the surge.  The distributor got plumbed for manifold vacuum to eliminate all of the possible leaks in the vacuum hoses and the possibility of the vacuum advance dancing around because of a varying vacuum signal.  Along the way I picked up a NOS set of the welded steel exhaust manifolds as a safety since the Rockwood is our full-time home.  However I was lucky in that I was able to remove all of the A.I.R. fittings and install the 22mm oil pan drain plugs.  I need to install a fuel pressure gauge at the carb next . . .

[circleD]

The smog pump is the same as the EGR correct?
To make sure we're on the same page# in the same book   

[pvoth1111]

No its not.....EGR.....exhaust-gas recirculation
But is related.....and maybe interconnected. 

[cncsparky]

Here is my project thread that has a lot of the info you request.


http://www.classicwinnebagos.com/forum/index.php/topic,9139.0.html


Fire away at any questions you may have.

[circleD]

That's the thread I've been looking for sparky to give to others for info.

[bluebird]

I don't remember if they were 3/8 or 1/2 pipe plugs on mine. Been too many years ago now. I did leave the vapor canister on mine. All I removed was the duel fuel setup and the air injection pump. Didn't help the mpg much but it did run much better. 

[1990HR]

With a TBI system, did anyone get a check engine light?

[DaveVA78Chieftain]

I have 2 vacuum gauges so I monitor both manifold and ported vacuum on my stock 440-3 with Thermoquad.
Ported vacumm only drops to zero at idle.  Off idle and at all other pedal positions, the ported vacuum performs exactly the same as manifold vacuum.  The reason ported vacuum is different at idle is because the hole is above the throttle plate.  Once the throttle opens, the same vacuum is felt at that port as is seen at the base of the carburetor.

It is important to understand that vacuum advance is placed on top of centrifugal advance. If you are running at 2500 RPM with 32 degrees total advance (8 degrees initial + 26 degrees centrifugal) and engine vacuum is inducing a total of 20 degrees vacuum advance, the sum total  of advance is 52 degrees. In the days of leaded gasoline, 52 degrees was the absolute maximum value of advance.  On today's gasoline, a maximum value of 50 degrees should be utilized  Anything greater is detrimental to the engine.  The amount of vacuum advance change is dependent on engine loading.  As you step on the pedal, engine vacuum drops therefore vacuum advance decreases.  As you approach a steady speed on level ground, engine vacuum increases therefore vacuum advance increases.   The changes in engine vacuum are also accompanied by a change in A/F mixtures by the carburetor.   Richer mixtures (13/1) used for power reduce detonation (ping) whereas leaner mixtures (15/1) promote detonation (ping).


From http://chevellestuff.net/tech/articles/vacuum/port_or_manifold.htm:

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it. If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

[DaveVA78Chieftain]

Not sure I can agree with 18 plus manifold vacuum at WOT. 
Max manifold vacuum is around idle;
0 or near zero manifold vacuum at WOT.  With the throttle wide open, the manifold "pressure" is very close to atmospheric pressure.
Now if your referring to the vacuum effects to the venturi section in the carburetor, then I can understand what you are referring to.

From How to Rebuild and Modify Carter/Edelbrock Carburetors:
Can you have high venturi vacuum at the fuel dispersal ports at WOT?  Yes, however that is due to the venturi effect within the carb itself which increases the air velocity decreasing the air pressure (more vacuum in fuel passages) allowing "atomized" fuel to be pulled from the fuel bowl.   Once the air passes the venturi section the bore opens out resulting in the air velocity decreasing and air pressure to increase. 

So, even though the manifold vacuum moves toward 0 at WOT, fuel regulation, via the venturi effect, is maintained.  Even though manifold vacuum is close to 0, it is still lower than the atomized fuel (which still at outside air pressure (e.g 14.7 psi) so the fuel mixture is vaporized when it enters the manifold.

PS: Enough of a positive spin TJ?