308QV (US) Air Injection

It's one of those situations where the components might all cooperate, or the last one is a pain to remove. I'm referring to the 2-valve motors. I had one particularly stubborn one, but I managed to get it out with patience and the right tools. It didn't seem badly deformed, as it was a close fit. The ones that came out easily could rock slightly in the bore. Using a thin backup wrench to get the manifold off of the injector was key. The 4-valve setup does seem like an improvement.

These pieces help tremendously with emissions. The 308, with working SMOG equipment, is more pleasant to drive in my opinion. You can open the top and get caught at a traffic light, and the horsepower drop is minimal. Also, I've noticed the 308 taillights stay much cleaner. The check valve opening pressure specification is 0.5 psi, and the actual pressure in the headers is best measured in inches of water. The work or energy, and corresponding power (work per unit time), is insignificant.

On the flip side, more engine components mean more clutter and more to monitor. I've heard horror stories of air pumps failing and seizing, such as a case where one locked up and jammed the R-bank exhaust cam.

Additionally, air pumps are not really serviceable. They can't be oiled, and rebuilt ones are a waste of time. When I encounter a problem, I buy brand new parts from GM, including check valves.

 

That QV hardware looks brand new.

 

Ok......so now what I am wondering is on the QV cars, if I am able to get the injector out with the manifolds left on, if there is any debris falling off the injector when it is pulled out, is there danger of stuff getting lodged in the exhaust valve?

 

Little chance if any and if it does it will just be blown out first time the cylinder fires.

And there is zero chance of getting injection nozzles out with manifolds on.

I see no valid reason to remove air injection. Its very benign and substantially reduces exhaust emission. Of all the emission systems it was one of the smarter and more effective ones.

 

#1 - Great.....thanks.
#2 - NUTS........I guess this will be a winter project.
#3 - My injector rails are currently plugged with Caps on the ends. Air pump, pulley, belt, and hardware was removed before I bought the car. I was afraid that the rails would rust out and cause an exhaust leak. Would it be advisable to just leave the injectors in place and after removing the air rail cap the injectors off?

 

Six of one and a half dozen of another IMO (about the same functionally as using the specialized plug on a 4V), but it takes more than just a cap as you really need the correct size metal ball being held into the female "V" seat of the nozzle by the cap to form the seal (as the straight threads of the cap won't seal) -- similar to what this Fchatter did on some 2V air injection nozzles (but I would not call that equivalent to the 2V specialized plug as the exhaust port is still very obstructed):

 

Is it correct that air is sent to the injection nozzles only until the engine warms slightly where thereafter it is sent to ports in the catalytic converter?

I am just wondering how badly emissions are affected if the injection nozzles are blanked off and air is only sent to the catalytic converters.

 

Lots of interesting info here since my original post. On my 84 QV, I'm past the time (for better or worse) to reevaluate whether to remove the injectors and plug the ports on the manifolds as I have already done it and put the engine back in (btw I don't see any way this can be done with the engine in the car). Now that I'm reassembling everything else, the only advice i've found on FC is the general instruction to "remover everything" associated with the air injection system. I'm trying to confirm what that encompasses exactly.... I plan to delete the cut off valve and solenoid and all associated hoses, cap the hose ports on the throttle valve and the air box where two of those hoses go. I had thought I could still put the CAT back on. I'm looking to confirm if anyone knows if this is all seems correct, and if there are any electrical connections or anything else I need to modify?? Has anyone found any specific instructions?
Greatly appreciate all your advice and comments,
Marc

 

Air to cats was only done on 80-83. Air to cats was a miniscule improvement. With no O2 in any of those air injection was not turned off when warm. It was full time.

 

On a somewhat related topic: can anyone tell me if the air pump drive shafts for 80-82 2-valve and 83 QV engines are interchangeable?

 

@Rifledriver, sorry if I'm being dense, but I assume you mean since no air to the CAT in '84, removing the CAT and putting in a test pipe has no effect and is not necessary, correct? Also here is an image of the wires that were connected to the solenoid and switch I am talking about. Do the wires need to be terminated in some way, or just left disconnected, since I'm not reinstalling it?


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What do you mean by "air pump drive shafts"? The main shaft inside the air pump itself or the funny little breakable shaft they added to the US 1983 system (doesn't exist on 80-82 US)? I believe the later 81-82 US and 83 US use the same air pump (F part number 117545), but it's a standard GM? "US" air pump so just replacing the whole thing is best/least hassle/least expense. Please clarify what you are doing.

 

The electrovalve with the pink and beige-black wires is the electrovalve for running the air injection system when cold, but, as Brian indicated, on the 84-85 US and 328 US there is no reason to disable the (pulse) air injection system as it only operates when cold and really has no impact on performance at all. The diaphragm item with the yellow-green and beige-black wires is the differential pressure switch that "squirts" the cold start injector during cold-running throttle blips -- it is not part of the air injection system and should not be disconnected. Almost unfortunately, they used the same vacuum source to operate the electrovalve and the differential pressure switch. People often wrongly disconnect the differential pressure switch thinking that it is part of the air injection system -- it isn't!

 

Better reread what I said because I made no such statement. In fact I really have no idea what you mean.

 

I do have to say I find it amusing you guys are busy stripping a system out of a car when you clearly have no idea what it does or how its doing it.
Reminds me of the early days when people took out and plugged up PCV systems because they were evil government SMOG and did a lot of damage because an engine needs crankcase breathing. The more positive, the better.

 

Thank you all for the input and direction on this. Appreciate it.

 

Thanks Steve. I’m referring to the funny little breakable shaft. I acquired one as a back-up recently and just wanted to confirm it was the correct one for the 83 US QV; I didn’t realize the 2-valve engines did without them. Out of curiosity, how are the air pumps driven on the two valve engines?

 

Just driven directly off the end of the 1-4 exhaust camshaft on all the 1978-82 US 308-2V. Only the 1983 US 308QV/MondialQV have it -- it was a "fix" to prevent having a timing belt failure if the air pump seized up.

 

Thanks again Steve.
When the air pump on my QV seized, the result was a melted belt, a missing tension pin at the air pump drive pulley / funny little breakable shaft interface, and absolutely no damage to said shaft.
I assume the pin either vibrated out or simply fell out of its bore when the alloy pulley heated up and expanded due to friction with the stationary belt. ‍♂️
Either way, I’m hoping that was less stress on the camshaft than the funny little breakable shaft needing to twist itself in two.
Also interesting was the fact that neither the belt nor the air pump gave any indication of failure before or after: no funky noises from the air pump prior to failing and no squealing from the belt once it did fail. It was just a normal Sunday drive until the next time I took the car out and noticed something didn’t look quite right in the engine bay.
Definitely paying closer attention to the air pump from here on out. ‍♂️

 

80-82 the belt was supposed to be loose enough if the air pump went south it would kill the belt and not overstress the timing belt.
Too many hands on cars they had no business working on and that idea was replaced with a sacrificial shaft that caused nothing but problems.

 

Hopefully you guys will indulge one more inquiry on this from me. When the car came into my possession, the electrovalve and diff pressure switch were wire tied to the frame as you can see in the picture. Hard to believe that's the way they were mounted originally. Or were they? Or was there an original position/location for these and they might have been relocated to here by a previous owner? Thanks again.
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