I am alsmot done with my TFI to DSII conversion on my 84 F150 2WD 300 I6. I however can't figure out where to plug in the vacuum line from the distributor. Does it go to the carb, carb spacer(or base), or to the actual intake manifold?

The carb I am using is the TFI carb, which I will unplug,( except for electric choke)

IF anyone has PIC, that would be awesome.

 

I don't have experience with your I6, but I am in the process of debugging my DSII vacuum advance and can tell you that in my application it connects to a ported vacuum switch on the top of the thermostat housing.

Ford p/n E1AE-8A564-J2A , or a Standard Automotive Products PVS-20.

This is so I can keep all my 'smog' functioning.

If you were to just do it yourself I would recommend connecting it to "ported, or, timed" vacuum on your carburetor, above the throttle plate so it only sees signal when the butterfly's cracked open.
You wouldn't want it to see full manifold vacuum.

HTH,

 

Jim, I don't I have a port on the thermostat housing, probably just the difference with the I6. So what your saying, is find a port on the carb that creates vacuum only when rpm's are elevated?


I would imaging the intake would create constant vacuum, that only increases with higher RPM's.

Also I am thinking to much vacuum at high RPM's shouldn't be a problem, because the dist diaphram will only advance (technically retard) so much.

 

No, at part throttle.. the centrifugal advance helps take care of higher rpms, you just don't want the two added together leading you into detonation.
No, actually manifold vacuum will drop as the throttle plates are opened, less so if the carb is drastically undersized.
Yes, of course advance (retard) is limited by the 'can'.
That's my problem now. Too much vacuum advance, and at the wrong time.
That's what lead me to look at your post.

The signal at a port just above the butterfly will peak just as the throttle opens, taper off, then come back some as the engine gains revs and pulls more volume through the venturi.

Sorry if I was unclear on that.

This one post on another forum combines articles from Rein-car-nation, 460ford, Ford Muscle and others.
I hope it's ok to post this link here, and is not violating rule #7....
I'm not promoting somewhere else.
http://vb.foureyedpride.com/showpost.php?p=244542&postcount=1

Lots of information on recurving and vacuum advance all in one place.
I hope this helps you understand, and I'm not just confusing you.

Hopefully someone who has done what you are doing will chime in soon.
Have you tried searching the I6 board? I'm sure there's a Guru there that could help you, if you can't find it on your own.

 

The vacuum advance hooks to a port on the carb that has no vacuum at idle, but does have vacuum when the engine rpms are increased. You can try to find a port like this on the electronic carb, but ideally you need to get rid of that carb. It has an electronic mixture control that may not work now that you have changed the distributor. You can try it and see what happens.

The way the timing works; You have your initial timing, and the centrifugal timing which advances the timing based on rpms. The higher the rpms, the more advanced the timing.

What the vacuum advance does is advance the timing based on engine load. It advances the timing over and above the centrifugal. The engine can take a lot of timing when the load is light. When the load is light, the throttle is partially shut, which makes the vacuum high, so the timing is advanced way beyond what you would normally think, way up in the area of 50 degrees BTDC. This gives good efficiency and fuel mileage.

But 50 is way too much if the engine has a load on it. When you start to pull a hill, and push on the pedal, the throttle will open more, the vacuum in the engine will drop, and the vacuum advance diaphragm will relax, retarding the timing back so the engine will not ping.

 

Franklin2,

Excellent post. I don't think I've ever read a more thorough yet concise explanation of engine timing. Well done.