So does my 84 460 have an adjustable vacuum advance. I put a new cam in my truck and think it is pulling more vacuum then before as when it's cold it idles rough as it always has as my choke is not hooked up the as it warms it hits a spot where it idles really nice and reves up really nice then as it warms up even more it will die and will not start back up. Tonight I unplugged the vacuum line and plugged it and the truck started back up for a few seconds before it dies again. As before where it would not restart at all. Thank you for any help.

 

Is that a performance cam? Vacuum at idle is quite a bit less compared with a stock cam, not more.

 

Why not properly connect the choke?

Are you sure you do not have a vacuum leak from R&R'ing the intake when you did the cam?
Sometimes the engine warms up and leaks appear from 'nowhere'.

Were you able to properly break-in the cam?

 

The cam is a mild rv cam. I was able to brake in the cam right. I originally thought it was a vacuum leak and after tightening the intake down some more it sealed up and started better. When it stops raining I was gonna use starting fluid to find out if it has a vacuum leak. I was gonna check by the big vacuum line on the back of the intake as well as the major joints. When I replaced the cam I remembered I used a hot pressure washer on it. Is there something that could been messed up by that

 

Your truck has 'hot fuel handling'???

It would fit the symptoms of firing up and soon dying.

The inertia switch sends power through the fuel pump relay.
The oil pressure switch sends power to close the relay.

But! When you are cranking the engine over power is sent directly to the tank selector relay through a pink/black wire.

So, the carb would fill with fuel and when you let off the key the fuel would stop.

Check the wire going to the oil pressure switch at the back center of the engine.
(I think it is red and orange, but not sure of an '84)

There should always be power in run to one side of the switch.
When oil pressure builds the switch closes and sends power to close the fuel pump relay.

The inertia switch should have fused power.
If no power going TO the inertia switch, check the fuse.
Check the reset button.
Power then goes to the fuel pump relay.
(I think this is a yellow wire, again not sure '84)

The fuel pump relay should close with the engine running.
Sending power to the second (tank selector) relay.

The pink/black wire should be spliced in between the two relays.

Maybe it is as simple as too much water in the socket causing the pump relay not to close.

If it starts while cranking the selector relay is good.

Things definitely point to a slipped or otherwise bad sealing intake gasket.

Do you have a vacuum gauge?

 

So my truck did have the hot fuel set up. When I first go it it was not working right a buddy had a holly blue that he sold to me for cheap. I wired it directly to a twelve volt keyed wire. I know the carb is getting fuel. I do not have a vacuum gauge.

 

And you only have one tank?
The selector relay still needs power to switch, no?

Otherwise, I would say your ignition module is toast.

 

I do only run one tank. I will look into the ignition module as well as use the ether to try and find the vacuum leak.