1981 308 GTSi - Air Injector nozzle removal criteria

They can deteriorate enough for partly break away but they go out the exhaust manifold, they won't go back upstream to the cylinder. They can be there intact for decades of non use and still be in one piece. Removal can be problematic as they are pretty difficult to access and rarely unscrew without a fight. Plugging the hole is easy, most people just screw in a stainless steel plug made to the dimensions shown. If a more through modification is desired an over length plug is inserted and the protrusion into the exhaust port is marked, the plug removed and trimmed to the mark and reinserted resulting in a smooth exhaust port wall. In that case each plug has to be identified as to it's cylinder and only used in that position forever more.
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I’ve got concerns about the air injection system, as well. I just purchased an ‘81 308 and while the exhaust/emissions system seems to be intact, the smog pump belt has been removed. The pump turns freely. What’s the benefit of removing the belt? What negative impact could be expected for continuing to run without the belt? What effects (positive or negative) would be expected if the belt were to be reinstalled? I’m not in an area that requires inspections for this vehicle (emissions or otherwise) so for now I’m only concerned with preventing future problems. If ever I’m forced to remove the engine, though, I’d strongly consider removing the entire air injection system and installing proper plugs, since overall it seems like it could be a time bomb of sorts.

 

The system will collect condensation and rust out. Eventually the check valves will rust out and exhaust will back flow and burn stuff up.

Many of those parts are hard or impossible to find and have become quite valuable. The pump being free is a very good sign rust has not taken a big toll on it yet. If not needed where you are I'd take it all off and either pack it well away or sell it for a restoration project or someone who needs it to keep a car registered.

 

The attached article appeared in the Dec 1994 issue of the FML, and discusses many of the issues related to the air injection system on US version 308 2-Valves. I agree strongly with Brian -- either keep a complete, well-maintained working system, or remove the entire system (including the air injection nozzles) to preserve (or sell) the components.

 

The car’s got 35,000 miles on it now and I’m not sure how long the belt’s been missing. Would it be inadvisable to install a belt and restore system functionality? Or is it likely that the system’s already suffered enough damage that installing a belt would do more harm than good?

 

Reinstalling the air pump belt won't do any more damage to an already degraded system, but you need to make sure that the air pump itself is in good condition and free to rotate well. The downside to this design (where a cam is used to drive the air pump) is that if the air pump seizes, this can cause the timing belt to skip teeth and/or strip teeth (or the air pump belt might break). On the 1983 US models, they added a shearable coupling between the cam and the drive pulley for the air pump belt to deal with a seized air pump, but on 1978-1982 US models (I believe) it's a strong direct connection.

 

“On the 1983 US models, they added a shearable coupling between the cam and the drive pulley for the air pump belt to deal with a seized air pump”

Does anyone know if this shearable coupling can be retrofitted to earlier models like my 1981?

 

I think the short answer is "no, not with any sort of reasonable cost/effort" -- there are some fairly serious design differences. This is your US 308i-2V where the oil seal (item 52) has a large diameter riding on a large diameter built into the exhaust cam:

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Whereas, on the 1983 US 308QV, they added another cover (item 39 on TAV 5) to hold a small diameter oil seal (item 56 on TAV 5) riding on a small diameter of the cam -- so significant design changes to both the cylinder head and camcover in that area (as well as the cam end):
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It is interesting to see the item 71 coupling (119215) on the 1983 US 308QV (TAV 9) that transfers torque from the cam to the hub holding the pulley where they just necked it down to a very small diameter meant to shear before anything bad could happen to the timing belt if the air pump froze:
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Steve, thanks for the detailed and very informative reply. I suspected it wouldn’t be a simple upgrade.

I just read in another thread where air injection causes the exhaust valves and headers to run hotter and tends to not do any favors for the sodium valves.

It would seem that no matter what I decide to do (short of removing the entire system) I’ll eventually be in for some type of grief.

I need to just get of the forums, go drive the thing, and have fun with it until it breaks

 

On the cars like yours it was pretty SOP in the dealer network to tension the belt on the loose side. It would slip and hopefully be noticed before any other damage was done.

As far as the air injection having any ill effects to the engine that is not supported by any data and reaches well into wives tale country. I was replacing broken Ferrari exhaust valves on cars built long before Ferrari ever had air injection and the rate seemed no higher after it was implemented. The theory ignores a lot of science. Air is injected into a forge to make the fire hotter. It has no chilling effect.

 

Ah, I like that idea. I’ve ordered a belt and I’ll tension it on the loose side. Brilliant! Thanks for your reply.

 

There should a couple of easy ways to make system fail safely at either pulley by making one of the pulleys shear (aluminium or high temp printed plastic with lots of holes) or use fasteners that are slimmed down under the heads and tightened less (with Loctite). Loose belt sounds the easiest though.

For the OP I would leave the air injectors in there. Taking them out may cause more problems as a few are bound to be distorted from heat and/or corrosion and may break trying to remove them.

 

Installed the belt yesterday, drove for 75 miles, no unusual noises, and the belt’s still intact. Not that I’d likely be able to hear anything over the exhaust noise, anyway