One-wire HEI conversion & ECM questions

[macdude443]

I am looking to disable the ECM (as it doesn't seem to work at all) and install the Skip White HEI distributor.  I have the same one on my SX/4 and it works nicely.  I plan on replacing the Carter feedback BBD with one that I completely dipped and rebuilt (also a Carter feedback BBD model).  I will keep all of the emissions equipment that the computer didn't control.  Judging by the vacuum diagram, I will be losing the vacuum switches and solenoids, so the pulse air system will have to be removed.  All else (EGR, PCV, Vapor Canister, Trap Doors) will be hooked up and (hopefully) functioning.

I will disconnect the ICM, disconnect the stepper motor leaving the pins fully into the carb body, disconnect all solenoids from power, disconnect vacuum switches from ECM and remove the distributor.  Then I will find 12V for HEI, install HEI, swap carbs and plug all vacuum lines at the carb (for now).  Then I will set timing and connect the vacuum advance.  From there I will tune the carb until it drives well, then start reconnecting the rest of the vacuum lines.

My questions are: 

 -With the HEI, do I want ported or manifold vacuum?  If ported, is that the 'S' port on the Carter, on the valve cover side in front of the choke?  I assume S is for "Spark".
 -What do I do with the remaining pulse air system?  Can the vacuum port simply be plugged?  What about the line going into the cat?  I don't want any fires!
 -Is the Sol-Vac triggered electrically by the A/C?  Will it still work when the A/C is turned on, without the vacuum solenoid connected?  This might not even be necessary at all.
 -There are two vacuum lines coming out of the firewall above the steering column, one has a purple tracer.  They are 3/32 or 7/64 size.  Is this the Cruise Command?  How does that work?

Lots of questions!  The car is completely stock '86, I6, auto.  I've never removed all this stuff before, as my SX/4 was gutted when I bought it.  I have attached an image of my vacuum routing diagram.  The Eaglepedia has been my friend so far.

[Draekon]

-With the HEI, do I want ported or manifold vacuum?  If ported, is that the 'S' port on the Carter, on the valve cover side in front of the choke?  I assume S is for "Spark".

There is a lot of debate about whether to run ported or manifold vacuum.  One thing that a lot of people overlook in this debate is how the distributor is set up.  For example, the stock distributor produces very little mechanical advance but a great deal of vacuum advance.  It was set up to be run on ported (or a mixed) vacuum system.  With a lot of HEI distributors, they have enough mechanical advance to run the engine properly on its own, and the vacuum advance adds a little bit to help with emissions in low throttle (high manifold vacuum) conditions.

But I don't know how the Skip White distributor is set up.  If you want to play it safe, run ported vacuum (which I believe is the S on the diagram you are referring to). 

-What do I do with the remaining pulse air system?  Can the vacuum port simply be plugged?  What about the line going into the cat?  I don't want any fires!

You should not remove the pulse air system.  Without it, you can burn up the Cat rather quickly.  I would leave it on full time (bypass the solenoid) before removing it completely.  But if you do choose to remove it, the line to the exhaust should already have a check valve on it, so there should be no risk of shooting anything backwards up the tube.

-Is the Sol-Vac triggered electrically by the A/C?  Will it still work when the A/C is turned on, without the vacuum solenoid connected?  This might not even be necessary at all.

The Sol-Vac has two forms of operations.  When there is a high electrical load (e.g A/C on), the Sol-Vac is operated to increase idle RPMs (I think up to 900).  The vacuum portion of it is for if the idle RPM drops down to 450 or if the air cleaner temps are cold.  In that case the vacuum portion of actuated, bringing RPMs up to around 1150.  You should be able to just run the electric part if you wish.

[macdude443]

Thanks for the info.  Regarding Pulse Air, there are two lines with what look like large, vacuum operated check valves(?).  They are hooked up now, so I'll just run them straight to manifold vac?

How does the cat burn up?  If I replace the cat with a non-tube model, can I eliminate the line and valve to the cat?  Just seems strange to me to run it constantly all the time.

[Draekon]

I could be wrong about the cat burning up, I just thought I read something about that at one point.  Either way, if you remove the pulse-air system, there may not be enough oxygen for the catalytic converter to clean up the exhaust.  But if you don't have to worry about going through a sniffer test, it may not matter (aside from the legalities associated with removing emissions equipment)

As for it running all the time, I believe when the car is up to operating temperature, and everything is running correctly, it already operates all the time.  But in the dual systems (two pipes) it chooses where to dump the air (exhaust pipe or catalytic converter) depending on the vacuum load.  The pumps do not create much pressure, so it should not decrease performance having it constantly pumping air into the exhaust.

[carnuck]

The cat clogs up and then overheats. Switching to a high flow cat is best. I have one for my Eagle because the old one did that and cut out when climbing the hill to my house.