84 F-250 - 351W/5.8L - 2B Carb - Duraspark II

The original single vac distributors pin holding the gear (dont know what its called) to the shaft that triggers the magnetic pickup broke so I replaced the whole distributor

The parts store gave me a dual vac and I put it in leaving the plug in the 2nd Vacuum hole and hooked up the vac line like the original was.. I have not been able to get the truck to run right since..
For one thing the Vacuum advance advances it so far that it wont run (has vacuum at idle, and it didnt before when i tuned it up) so I plugged it and left it off.. It pops and jerks and has no power and has random backfiring especially decelerating.. I havent been able to get it running right no matter what i try.

Yesterday I took the belt off of the really noisy Air Pump and the truck runs better but still pops and jerks, I think maybe it was freezing up or something bogging the motor down and amplifying the misfire problem but that made me wonder about the vacuum at idle suddenly happening too.

My questions are..
*Can the dual vac replace the single vac distributor as is,
**If not can the vacuum canister be replaced from 2 to 1 vac and work right or replace entire distributor again
***Why would vacuum suddenly start (i didnt change the hoses around)
****Is the air pump really necessary
*****Anything that could help

I hope this makes sense...

 

Tell the parts store to give you the right distributor, then make sure it is installed correctly. It sounds like the replacement is totally wrong.

As far as using it, the outboard hose is the vacuum advance, the inboard one is the retard. As for the vacuum suddenly starting, the old advance may have been bad.
Air pump, it depends on where you live and what the laws are.

 

Definitely the WRONG distributor.
Have them make it right.

How rich is it running?
Sounds to me like you've blown the powervalve in your 2150, if the timing is remotely correct.
If not, you will blow it soon if you keep running it that way.

 

Timing is correct.. Been over and over that one...

It runs pretty rich, ya can smell it pretty good but it isnt flooding out to the point where it wouldnt start or run, I couldnt find any Air/Fuel mixture screws on it though, when i set the timing i just corrected the idle with the idle screw and that was it.. Oh, i dont know when that vacuum thing is supposed to actuate to the linkage but it isnt doing it at idle, it works when i put vacuum to it but i dont know if it works when it is supposed to..

Replace distributor with right one.. check.. kinda saw that one coming..

The powervalve is probobly something i should let a carb shop look at for me..
I dont know if it is hard to do, but if it is just a tick over kindergarden level carb repair, I'll be in trouble fast...

The laws in Oregon say I do need pass DEQ Air quality check every two years and the smog pump is needed in order to do that... BUT for the other 729 days between DEQ checks do I really need the air pump for the truck vacuum and stuff to function... Point is, I dont wanna buy one until i have to, either that is now, to make the vacuum stuff work right, or in a couple years to satisfy DEQ.

 

The air pump should not affect the vacuum, however, you probably need to check that everything is connected correctly according to the emission label. You are dealing with nearly 30 year old vacuum lines. Depending on where the truck was originally delivered, you may have a CA spec truck.

 

Replacing the power valve is easy. You just remove the carb from the truck (it's on the bottom side, has a cover over it with four screws), take the cover off, unscrew the old valve, screw in the new one, and put the cover back on with a new gasket.

Mixture screws are on the bottom front of the carb. When you go to replace the power valve you'll see them.

 

"Carb shop", really?
Do they still exist???

The A.I.R. pump is only used to provide additional oxygen to the Thermactor ports on my engine.
It may also be connected to the Catalytic Converter on your truck (if it came with one)

You should be able to see if the Powervalve is dumping additional fuel into the throat at idle.
But it is a bit of a 'chicken & the egg' problem.
Too rich, and vacuum will suffer.
To little vacuum, and the Powervalve will open.
But, if the timing is off, and it backfires through the carb, it will blow the diaphragm for sure.

 

thanks.. i watched a video on youtube about changing the powervalve.. I think i can handle it.. I have replaced some of the vaccum lines..
Heres one for you guys.. In the 3/8" hose between the crankcase cover and the pcv valve was a metal valve or something that was leaking, i couldnt find anyone who knew what it was and one guy at a parts store said it was something someone put on that didnt go there so i took it off.. Does anybody know what that might have been?

 

The Positive Crankase Ventilation valve usually fits in to the grommet in the valve cover.
Then, a hose or tube connects to manifold vacuum at the intake or the base flange of the carburetor.

The 'thing' could have been a oil separator.
Sometimes if there is a lot of blowby in the engine or it is used at very high rpm it becomes necessary.

Who knows? Could you post a pic?

 

Replaced Distributor.. Having problems finding a power valve, but thats a whole new thread

 

How sloppy is the timing chain?

 

I havent really investigated that although it has crossed my mind that it possibly jumped time.. It was running great before the pickup gear thing on the distributor came loose and hasnt been the same since, so i kinda hoped it would be an easy fix, like maybe the distributor caused the timing to be off causing a backfire that caused the power valve to blow out..

after i locate a powervalve and get it in i will go on from there.. O'Reilly's and AutoZone and Carquest so far hasnt had one Oreilly's has it on thier computor but none in stock or to be ordered the other two dont even know what I am talking about.. Gonna try Baxter's and Kneckt's tomorrow..

Its tough because its my only vehicle so I wanna have it down as short a time as possible..

 

I think my seat ate it.. I will dig it out and get a pic of it because i am very interested in what it is.. So far nobody that has seen it has any idea...

 

I dont know that the power valve is blown, but it is a possibility if the truck is running pig rich.
Valve timing being off is another option, and would explain poor vacuum.
Try removing the distributor cap and turning the engine over with a breaker bar.
Watch the rotor.
Then reverse direction and see how far you have to turn the crank back, to make the rotor change direction.

Usually I just look with my timing light.
Revving the engine and letting it return to idle.
The timing marks should advance and retard smoothly.
If it's blurry or jumps around you have an issue.