Hey everybody! So I purchased an 85 F150 with a 302 engine a couple years back for dirt cheap that needed a complete restoration and a new wiring harness (there was a short somewhere in the harness and the PO did a true hack job fixing it)! I actually started restoring it about a year ago and now I'm in the final stages of getting it on the road! After developing gray hair (and I'm 20) trying to somehow create a harness that would suit the TFI system, I decided to start looking for a harness from a donor truck. Many junk yards later and over 200 potential donor trucks later all I could find were DS systems. So I decided to just convert it to DSII, getting a new dist. tomorrow, got the harness, got the coil, and I think I'm ready to wire it up, however, I do know that the new dist will be vacuum advance, what I don't know is how the heck I install a vacuum advance dist into an engine that did not previously have a vacuum advance distributer! I know it can be done fairly easily, I just need to know how! And now a question that kinda scares me financially, will I have to get a new carburetor to do this conversion? I saw another thread on here that gave me basically step by step on how to wire it up, but I'm still very confused on how to install the vacuum hoses! Any help is very much appreciated!

 

Welcome to FTE! This is the place to be!

You didn't tell us what carb and transmission you have, and that does make a difference with a vacuum advance. But, let me explain.

There are two sources of vacuum used for the advance - ported and manifold. Ported simply means that the advance comes from just above the throttle plates on the carb, and there's no vacuum at idle. You should have a vacuum port on whatever carb you have, and a bit of testing should determine which it is. Manifold means just that - it comes from the manifold and there's vacuum all the time. And you should have a manifold connection on the rear of the intake manifold.

There have been fierce debates on here about which source of vacuum to use. Personally, I use ported as it gives the most stable engine RPM at idle. And, here's where the transmission comes in - if you use manifold vacuum and the engine is idling well in neutral, when you drop it in gear on an automatic the extra load lowers the RPM. But the lower RPM reduces the vacuum, which reduces the spark advance on most distributors, which further reduces the RPM, which reduces the vacuum, which reduces the RPM, which…. So, you've created a vicious circle and either the engine stalls if you started with a nice idle speed or you have to set the idle speed so high in neutral that it bangs into gear. Actually though, there are said to be ways around it, but not without knowing what you are doing.

So, long story short: Find a port on the carb that has no vacuum at idle and lots of it above idle and stick the advance hose there. You are done. And if you can't find one just tell us what carb you have, or post a pic of it, and we can probably tell you.

 

Hi Gary! Thanks for the fast response! That answers almost all of my questions! My truck is manual transmission, and the carburetor is a motorcraft, if you need pictures I'll get them up, I'm a newbie here so I'm not sure how to post pictures yet! Not sure if this matters for anything or not but this is another thing the PO did that irritates me, he took out the automatic choke and made it a manual for whatever reason, but that wouldn't interfere with anything I'm trying to do will it?

 

This is your carb, right?




If so, this is the vacuum port you want:




And the choke makes no difference.

Here's where the port comes out. I have the throttle open slightly to show that slot - otherwise it would be covered by the throttle plate, as you can see with the darker surface being what's open to the manifold at idle.

 

So this "restoration" was originally fuel injected?

 

Nope carbureted surprisingly

 

Yup thats the one I got! Perfect!

 

Another question, the cab I bought had an under dash wiring harness for an 86 diesel, would it have a plug for the engine harness to plug into or will I have some wiring to do? Or should I just go purchase the under dash harness from the donor truck I got the engine harness from? I thought it would have the plug but I can't find it, I have the under dash harness laid out in my living room (sorry mom) but I can't seem to find that plug, unless they used a different plug that year, I don't think it has it...

 

My guess is you should go get the harness from the donor. Apparently the diesel harness was different, which makes sense as there were things like glow plugs the gas-engined trucks didn't have.

 

That's what I was afraid of, I was hoping I would be ale to just remove the wiring for the glow plug and what not and have it be the same, silly me to think it'd be that easy! Haha to make sure I don't get ripped off, how much should I expect to get it for? He charged me 50 for the engine harness which I feel was a little much considering for DSII there really weren't that many wires...

 

You might send a PM to Diesel Brad as I think he could answer whether the harnesses are different. I only guessed. But, if you can't find the plug it must be different.

As for how much, I wouldn't have thought more than $50. It isn't a sought-after harness.

 

Ok cool, I'll contact him, I'm having some trouble now finding the correct vacuum advance distributer now as well, purchased one for an 84 and it didn't fit my engine... Grrrrr Any advice on finding the correct distributor?

 

Why didn't it fit? All 302's are the same.

 

That's what I thought too, but apparently not, the distributors for 84 and early 85's shaft was slightly shorter than the ones found later in 85, also, the part that seats down and comes in contact with the top of the engine was slightly bigger in 84.

 

People have wrote in before about the different shaft lengths, but I think it's a red herring. I think they work, I haven't heard any different from anyone. Unless you can find a different length oil pump shaft, I am not sure what the next move would be, the other style 302 dist's are all the same.