As I'm in the process of getting everything hooked up to the new 5.9 Magnum motor in my rig, I'm trying to figure this vacuum advance distributor out. I put the old distributor from the LA 318 in the new Magnum, and I labeled things as I disconnected them. Right now, I have a vacuum line that I marked "distributor", but I can't find anything that it plugs into on the distributor. Did I miss mark this? I thought our trucks had vacuum advance, but the only thing coming out of the distributor is two wires that plug into the wiring harness. Anyone got an idea where this vacuum line goes?

 

there should be a vacuum advance thing on the distributor. a line goes from it to the carb usually. should look like this.

 

Yep, that's what I was thinking I was looking for, but nothing. I think mine is totally electrical. The vacuum line that is marked "distributor", goes through the firewall into the cab. Maybe it's for the heater? It's probably just mis-marked (a friend of mine was helping that day when we took the stuff out, so who knows what happened).

Since it's clear that mine is electrical, without vacuum, does it still advance like a vacuum operated one would? If so, how does it know when to advance (I want to make sure I get the right things hooked up to make it work).

 

Your distributor evidently one for use the computer controlled spark advance also known as "lean burn". If is on your 87 the computor should behing the battery and there should be a vacuum line going to it.

 

That box is in the corner with the rest of the emissions stuff . Sounds like I need it to make it work, eh? Or would I be better off getting a regular vacuum advance distributor?

 

i would guess your truck originally had electronic spark advance which is why you don't have one. if you still have the original stock wiring and computer installed and working good i would not worry about it but if it has been switched to the 4 pin ignition system then you might want to see about buying one. your truck will run with without it but i think it would run better with one. some people even consider buying one of those hei vacuum advance distributors since they are about the same price as a normal distributor but you just have to buy a new 12volt coil.

if i was to guess that vacuum line is suppose to go the the vacuum tree or heater valve that might have been removed.

 

It sounds like I may have trashed the computer that the distributor needed to work. You mention the HEI ignition. I have the distributor that came with the magnum engine which has male connectors, so that should be HEI, correct? Although there's no vacuum control on that one either, it's just a couple wires hanging out, and that leaves me where I'm at now.

At this point I'm not sure what to do. I don't know if upgrading the ignition is a worthwhile modification, or if I'd get the same performance out of a cheap-o O'Reilly vacuum advance distributor.

 

was your truck still running using computer before you did the swap or does it have the 4 pin ignition system? i don't think the distributor that came with the magnum engine would work. when i was thinking HEI i was more so thinking of something like this. you just have to add ignition power to it and hook it up to a 12volt coil and it should run. you would have to use spark plug wires like the ones that came on the magnum.

 

Sorry, I'm not sure what the 4 pin ignition system means. As far as I know, it was using the computer before I yanked the 318. The computer is only for the ignition advance, right? If I put in a vacuum advance distributor, would I be okay without the computer? In the photos on RockAuto of the vacuum advance distributor, they still have the electrical connection, so I'm not sure what's going on there.

 

if your truck was using the computer behind the battery before then you would have to continue using that setup or switch to the 4 pin ignition system or HEI system. the HEI setup is cheaper than the 4 pin ignition system if you where to buy the parts you need. if the stock setup works then you could probably leave it for now.
a 4 pin ignition module looks like this

how it would be wired.