To Smog or not to Smog ???

if you don't need it remove it. the 'smog' or air pump pumps air into the exhaust stream to ignite the fuel rich environment, this will cause an increase in EGT's. there is two sides to leaving cats on as well, in my opinion i don't like cats on fuel management that can not be adjusted on the fly, carbs have no feedback so if you do run to rich the cats have a risk of catching fire. the aforementioned air pump was a way to reduce the HC by an 'afterburn' process and lessen that risk to the cats.

if smog is exempt i'd ditch the entire layout and go to a std exhaust without cats and smog eq.

 

Also, the smog pump on carb cars is only designed to run during warmup, after that, they are outta the loop. thats why they have a clutch on them.

 

They don't have a clutch. They run all the time.

 

The problem is that without the air pump running, the cats will age/foul more quickly. Consequently, when you state the alternative to stock as "remove the system entirely", this would mean removing the entire air injection system (including the air injection nozzles) and the cats.

Of course, maybe there isn't anything inside your cats now

 

They will not run cooler. They will run hot enough to work and will not be killed by the fouling Steve noted.

 

No -- as Scott said, the reaction that takes place inside the cat actually causes the cat to run at an elevated temperature, but this is what it is designed to do (and is best for the health of the metallic catalytic surfaces inside the cat).

If you remove just the air injection system, the cats will run cooler, but their effectiveness will begin to decline (i.e, fouling) until they just become "dead" pipes. Your engine compartment will be cooler, but IMO it would be better to use test pipes so that you can keep the cats functional for future re-use (keep all the bits if you decide to remove the air injection stuff - could be a critical issue for a potential future buyer).

 

A working air pump will increase the running temperature of the cats. This is due to a more complete reaction (I believe). I have verified this with a temp gun. I do believe that Steve is correct in that the cats will deteriorate quicker. I don't think that it is that much though, unless you are running too rich. I "generally" run with my belt off and the cats in place. I know the cats are working but are not as efficient as they could be with more oxygen provided by the air pump. Anyway, I have been running way for 10 years and then "adjust" the belt when needing to pass emissions and still pass with flying colors (and this is in CA).

 

Another consideration is performance without the smog equipment. It is my understanding that the earlier the model car that has smog equipment including the air pump, the more performance is to be had by deleting it. I have heard that the air injector nozzles are restrictive on any 308, but more so on the earlier years. Apparently, the earlier ones were larger and more obstructive to the exhaust than later ones, particularly on QV cars. So, it stands to reason that if you dont need to meet emissions, you could just remove all of it including the cats, and not worry about their heat or relative deterioration while enjoying a little more performance.

Good luck!

 

If its not required to pass emissions, and your keeping the car, I would remove the entire system. If the pump ever locks up it will stop the camshaft and wreck the motor. Without the pump running, the air nozzles in the head overheat as well as the check valve and air manifolds, shortening thier life. Pull the pump, all the plumbing, remove the nozzles and install plugs, and ditch the cats. Your car will be more reliable, will run much cooler, will get slightly better fuel economy, will have a very slight increase in power, will be lighter, and the biggest and best reason of all, it will be less prone to fire. All that extra heat helps to deteriorate hoses at an acclerated rate, and if a fuel leak develops its almost guaranteed to ignite. Put the 30 pounds of garbage in a box and hand it off to the next owner.

While the pumps dont have a clutch, and run all the time, thier only real effect is at idle speed. Dont let your car idle and problem solved.

 

I'm looking at an '83 308 at the moment, and it's got the emission pump sitting in the trunk. You can bet I lowered my offer a little bit when I saw that. I'd rather have the car complete when I buy it.

 

I was driving my 81 308 and the air pump froze up and I almost blew the engine. My mechanic said it skipped 2 notches on the cam. One more notch and the motor would be blown. I would never reinstall one again. It happened when I was driving down the road from picking the car up after my major service. That thin belt didnt break soon enough.

 

This is exactly what I was told by when I bought my ’83 QV.

 

Well, all the hope in the world wont change the laws of physics. The stock timing belts are rated to handle something like 12 HP IIRC off the Gates website. The fact they have repeatedly sheared off teeth and ruined engines that had no air pump running off the cam, should indicate they wont be able to handle to much additional load. That little belt will take a lot of tension before it snaps. The old Fiats had the same belt and the same stupid air pump running that same kind of silly little belt off the cam, and a whole lot ended up in the junk yard when that pump froze up. And its not an if, its a when.

 

And if your mechanic tensioned the belt correctly nothing would have happened.

To begin with air pumps dont just decide to freeze one day. They make noise for some time prior. Someone was ignoring the obvious.

Next the belt was way too tight. It should be obvious to the kid at the gas station the belt should, just like every other belt drive in existance be just tight enough to do the job. In the case of the air pump on the back of the cam that is rather loose. If done correctly the belt will just slip in the event of an air pump failure.

It is really not any different than blaming Ferrari for using aluminum for the oil pan because you overtightened the drain plug and stripped the threads.


I just reread your post.

That happened just after a major service???? You need a new mechanic. That affair was his fault.