Ya spark reading nowadays is tough with the differning crap in the fuel depending on the region unless it is really rich in which case they will always be black.
Here plugs end up near white on regular even with a good fuel air mix where as premium fuel will make them tan even when a bit lean. So reading plugs nowadays is crap shoot and what applies in one location may not in another.

 

I don't see anything good about EGR. Nothing. At all. Except maybe faster warm up in cold weather.
i don't see any reason for exceeding twelve, fourteen degrees initial advance unless

 

They usually will not crank over very well when hot if you go above 14 degrees. So I don't think there is much danger of him running it higher than that.

 

Yeah, initially I had it too high. The starter struggled to turn the engine when it got hot.
I retarded the timing some, and it seemed to have a different issue. It would just spin the engine around for a few seconds without starting, then when I let off the key it would fire up.
I'm going to a friend's house today and he's gonna help me dial it in to factory spec with a timing light, I'll see how that goes. We are also gonna check for vacuum leaks around the brake booster.

I took the belt off the smog pump the other day since I don't have a cat anyways. In doing so, I noticed the smog pump hose runs to the intake manifold. I didn't see any other connections from the smog pump to anything. Is it possible it was pumping air into my intake?

 

Unless some one botched something up it should not be going to the intake.

Some pics would help......

 

I did some googling and found that these air pumps usually have a line going to the cat and another line with a check valve going to the intake, for deceleration.
It was hard to find any real information about how my system was supposed to be. Some showed connections to the manifold or to the head, both of which I don't have. Since my exhaust connection is gone, I can't see anywhere else the air would go unless it's just blowing right out the side of the pump.

Here's a pic with some parts labeled. Air pump connects to a large fitting right next to the EGR housing.

 

Although it looks like it is going in to the intake it is actually going in to the exhaust via the EGR plate. It won't affect fuel air mix. You should also have a tube from the underside of the EGR spacer back to the exhaust manifold. This is what supplies the EGR it's exhaust gases. This set up makes EGR removal quite easy. But you will have to find a bung to block off the hole in the exhaust manifold.

 

 

Yup remove the EGR pipe and plug the manifold. If the EGR valve is good you can just unplug it. If it is leaking you will need a block off plate. The easier solution is to remove the EGR plate altogether and just install a spacer about the same thickness. Then you can start pulling stuff. If you are not intimately familiar with the system do it one step/one system at a time.
The lines that are no longer used can remove back to their source and then capped or plugged.
If you install a spacer to replace the EGR spacer plate. Unplug the EGR and cut the hose off the Air Pump. Remove the vac line (blue one on emissions sticker) all the way back to the VCV (vacuum control valve) and the stuff hooked to it
Then you can pull the Air Pump and is associated gear. On the emissions sticker the Air BPV (air by pass valve) is part of the air system. You can remove bypass valve and it's vacuum line to it the TVS (Temperature Vacuum Switch) . That will remove 75% of the emissions gear and will clean things up under hood significantly.
Do not toss any of the emissions bits as some bits are becoming quite rare and have some value to someone that needs them due to local laws.
The EGR pipe try to remove it one piece along with the EGR spacer plate. Bits like that are becoming hard to source.

 

Sounds like a good plan. I will probably get into doing all that eventually. I would be interested in de-smogging the motor.
For now, I might pursue getting the smog pump off there. Even though I'm not using it, I don't want it to get frozen up by having exhaust blown all over it without it running.

Another question is, will I need to change anything else to make the engine run right without this stuff? Someone mentioned that the DSII distributor has aggressive vacuum advance, designed for working with EGR. Will I have to get an aftermarket distributor?

 

The AIR system has a check valve that prevents exhaust from back flowing to the AIR pump provided it has not failed. The check valve in your application is just at the base of the carburetor the rubber hose from the air pump hooks up to the check valve.

And no you do not need a new distributor you would just need to replace the vac advance unit with an adjustable one if yours is not adjustable, but some of the factory ones are adjustable, as are most of the aftermarket ones.
It is a relatively simple job to do. I would only do this is you have issues like pinging.
Set at the factory base timing I doubt you will any issues as it is a rather conservative 6° BTC, if you start bumping up the base timing you may encounter problems.
What people don't realize is the ported vacuum of the carb is manifold vac once you get around 1000 RPM so advancing the base base timing with the factory vac advance can cause issues.
Once you get the emissions pulled and have checked for adequate fuel air mixtures that is when you can start playing with timing for more power or better fuel efficacy. If following the above for emissions removal will leave you with what is basically a mid 1960's set up with the addition of EVAP.

Recurving the distributor is simple to do but can encompasses a lot of trial and error and can be labour intensive when done in vehicle. As you may have to adjust it several times to get what you want.
With the relatively large 76CC combustion chambers in the 300 you total timing should fall somewhere between 34°-38° and be full in by 2500 RPM or so for optimum performance at WOT or are hauling.
But this is something you have to play with as every engine is different the 34°-38° total is a good base line to start at. Start at 34° total and slowly bump up the initial. You could easily pick up 6° of advance if you get 34° total at 6° BTDC.

 

Thanks for all the details.
I will probably try to do just that once I get my hands on the right size bolts/plugs to cap off the air pump and the EGR.

The notch marked on my distributor is right around 6 degrees BTDC. I had it set to that notch originally, and I got mild ping at part throttle before the engine had been warmed up.
When I disabled the advance and increased the base timing, I never got ping, but the engine became hard to start.
I switched back to advance today, and timed it to 7 degrees which is around what I had from the start. The vacuum advance affects idle RPM and timing significantly.
If the ping keeps going, I will definitely look into adjusting the vacuum advance. I would expect it to ping if I disabled the EGR as it is.

How can I tell if my advance is adjustable?

 

Since your system is not function properly you should disabled the manifold vac advance, that is the line I highlighted below in blue. Remove it totally and cap off the the vac port on the manifold. This will stop the vac advance form having any impact on idle speed and timing at idle. I suspect the check valve is NFG so might as well remove it and that vac line this will make it a more traditional and common set up just using ported vacuum for the vac advance... This may also solve the ping issue you were having..

 

Sounds like a plan, that makes sense to me.
I actually tried something similar a few days ago -- I capped off the ported vacuum source to the distributor, but it definitely was not right. I'll try capping the manifold vac.

I've seen many pics of 80-82 trucks running just one wire for ported advance.
What exactly is the point/effect of putting both vacuum sources to the distributor advance? It was my understanding that ported is roughly the same, except with no vacuum at zero throttle.

 

The way yours is set up from the factory when ported vacuum exceeds manifold vac it pulls through check valve making the vacuum to the dist equivalent to manifold vac, this is an emissions regime for use with the EGR as the EGR can cause the manifold vac to drop below ported vac. This set up is part of the EGR system, this is why in some setups if you retain the EGR but delete this you will get pinging when the EGR is active.

In your truck the check valve has failed hence the vac at the dist at idle. You don't want to just disconnect it but totally remove that vacuum circuit.

Ported vacuum is has much smoother transitions compared to manifold vac. If you charted manifold vac you would see it has a very jagged rise and fall as it changes with load and engine RPM, the vac advance will also show jagged changes in timing if hooked to manifold vac and will have a very jagged vac advance curve as it will react as fast as the manifold vac changes.
Ported vacuum has a much smoother vacuum curve between rise and fall so it short of dampens the transition so speak. .

So yes ported vac is equivalent to manifold but with much smoother transition.

One other area Port vac differs is at lower low throttle settings in this instance manifold vac is much higher than ported vac and could potentially cause detonation at loaded lower throttle and engine RPM settings.

Using manifold vac on a street engine can be an issue as above but also it will in all likelihood be pulling full vac advance at idle. . Now this does not see, like an issue at first
But......
The issue is on a street motor at idle (like at stop light or when the engine is cold) ) If the engine stumbles or has load suddenly put on it (A/C Alt etc) especially if is in gear like in an auto, the load /stumble will cause the manifold vac to drop that in turn reduces vac on the vac advance and reduces the ignition advance that will also drop the idle even further and in turn dropping the manifold even more, and again reducing timing advance yet again dropping the idle even further and dropping manifold vac etc etc...., and you could end up with a feedback back loop that will potentially stall the engine.