now when I adjust those do I just adjust one screw for optimum vacuum then make other 3 to match? Or do I have to adjust all 4 simultaneously?

 

They are to be done one at a time. Again make sure the dist vac is disconnected and the line capped. And be sure the engine is warm (at or near operating temp).

Start at one of the primaries and adjust it till max manifold vacuum is achieved then on to the next primary then do the secondaries. If the base idle speed changes (increases) after setting the idle mix adust it back down and then re-verify that the idle mix is correct and still set for maximum manifold vac in the same pattern as the initial adjustment.
Once done go back to the first primary you adjusted and verify it is still set to achieve maximum vacuum if not readjust and follow up with the others. And adjust idle as needed after each adjustment round.
You may have to do it few times get it set.

Then verify that you have little or no vacuum on the ported vacuum for the dist. If you do base idle setting is too high and the primary throttle plates are uncovering the ported vacuum port in the venturi.
So as you can see it can take a bit of time and is sort of like chasing your tail. But eventually, you will get it dialled in.



If you have any issues with still getting high vacuum on the dist ported after doing this let know and we will resolve that.

 

I just looked at your build thread and saw the pcv valve and breather cap. I assume that pcv pipe is connected to the intake manifold.

Nice lookin' truck.

May I suggest the following, as I think your focus is too broad at the moment.

1. Connect the pcv stuff and swap the dizzy vacuum advance from ported to full manifold, as already discussed.

This will in effect advance your timing quite a bit, and should allow a smoother idle.

2. Turn the carb idle speed screw whichever way is needed to get to 800rpms.

3. Assuming it will idle now, read the vacuum gauge. Post up the needle behaviour and vacuum level, or google how to read vacuum gauge readings.

4. This will tell you what needs to be addressed next.

5. Thereafter, you can dial in the idle timing, timing curve, vacuum advance, and carb.

The 1 1/4 carb screw settings will be fine as a starting point.

 

This was the what oil fill cap I had on originally

Plugged rear port in intake manifold. Will open it back up for tranny modulator

This was that original intake T deal. I’m doing away with it and running 1 hose direct to carb for pcv. Unless I must have this?

Plugged front intake manifold port. Going to keep it closed up for good

Pcv valve. Which I’ll run hose from here to front big port on carb

Plugged port for distributor. All ports on carb are plugged off as of now. Will fire her again this evening with more results

 

The oil filler cap, with a pipe connected to the air filter case, will be perfect.

The PCV pipe should not be T'd, so having its own dedicated pipe is also perfect.

The ported vacuum port on the carb, shown in the pic with the yellow cap, is above the lower full manifold vacuum port, and both ports are the same size.

Connect the dizzy to that lower smaller port, full manifold vacuum, for this evening.

I hope that makes sense.

It would look neater in the future if you use the rear intake manifold port for the PCV pipe. Just saying.

 

But don't use any of those rear ports if they are taking their signal from one single intake running only. A PCV system must use a common plenum area ONLY and never be hooked to a single running. Has the big potential for messing with that one cylinder's mixture.
It's ok to run a brake booster, transmission modulator or whatever other device needs vacuum. But not a full-flowing PCV system.

Paul

 

Some 428's used the dual feed PVC set up for reasons I can't explain. it was factory correct you had it right. . just plug it off and run to the carb as you said.

 

At idle at 800

2500 rpm

seems to be idling fine with all ports closed off and gauge on bottom port of carb



At idle

 

What kind of cam do you have in it ? you should be able to do a little better than that.

 

thats part of the problem. It was built 12 years ago. Guy has since died. Have no idea of where the paperwork went for it. It’s a crap shoot to be honest

 

Adjusted idle mix screws by the way of the vacuum gauge


This is the lowest rpm I can get with idle screw. So I may need to change timing?

This is at an idle after adjusting idle mixture screws. 900-950 rpm

Here’s 2500 rpm

 

Does it sound like it has a performance cam ? it's not a big dal either way but you're never going to get good vacuum if your cam won't let you.

 

Here is where dizzy is supposed to be hooked idling at 800 rpm



I can hit little over 20 on gauge at 3500 rpm

 

More advance will raise it , assuming your mechanical advance curve will allow it. that's why it needs to be checked.

 

Looks like you might have a rather a lumpy cam in it.

The Curb idle on most 428's from the factory was between 675 and 725 even the CJ drag pack fell in this range. They were at 6° base timing. So you could try backing down the base to say 8° or so.

Your cam may need manifold vac instead of ported also. Hard to tell without a cam card.