Hi everyone,

I'm new to this forum, but have gotten a lot of useful information from it so far. Here's a little back story on the car:

73 Valiant
/6 225 Auto
Sat for at least 3 years
Replaced:

• Holley 1920 carb
  Coil & condenser
  Ballast resistor
  Plugs & wires
  Battery
  Ignition control module
  Dist cap, rotor, vacuum advance diaphragm, reluctor wheel, pick up assembly
  PCV valve
  Thermostat
  Fuel pump
  Fuel line mod(thanks slantsixdan for a great write-up)
  Metal fuel filter
  A handful of other things that I can't recall off the top of my head

The car starts strong but idles very rough(jumps around between 1200-2000 rpms) and dies under load in gear. I replaced what appears to be 90% of the vacuum lines, but the small hose coming from the intake manifold and the one connected to the heater hose valve are not connected to anything. Also, the control valve, mounted on the firewall, and the OSAC valve are both dry-rotted and disconnected. I read the OSAC is supposed to be bridged between the vacuum advance and the carb, but not necessary. Can the control valve be replaced by a universal one? My main question is: where to hook up the intake manifold and heater hose valve hoses?

I plan on adjusting the valves and correcting the timing & air/fuel mixture, but the vacuum leak is obvious and I need to get it idling steady, at least.

Thanks in advance. This car is a pain, but I'm happy to be learning a lot about older models.

* I will upload images this evening.

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73 Plymouth Valiant

Here are images:

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73 Plymouth Valiant

Leave the OSAC valve alone and disconnected. Conect a vacuum hose directly from the carburetor's spark advance port to the distributor vacuum advance. What is it that you are saying "used to be" where there is now a circular blockoff plate next to the OSAC valve? This location usually has a blockoff plate on '73s (including my own).

You must cap off or connect that open nipple on the manifold vacuum tap or the engine will run poorly because cylinder #6 will be running way too lean.

Your photo "Vacuum port on vacuum (amplifier?)" actually points to the vacuum outlet port on the vacuum reservoir, which is for the heat/air conditioning system. This needs to be connected to the correct one of the "two dry-rotted hoses from here" vacuum hoses entering the firewall through the rubber grommet near the heater hoses. The other one of those hoses gets connected to the heater control valve. Determine which is which by experimentation; if you get it wrong the heat/air conditioning system won't change modes from floor to panel to dash top when you operate the lever with the engine running.

I don't see any mention or photo of what you've done with the car's EGR system, so I can't advise in more detail on that yet.

Tune-up parts and technique suggestions in this thread. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

The small vacuum port on the intake manifold was used to control the doors in the HVAC system under your dash. I see someone has cut and capped the lines for the AC evaporator under the dash. This renders the AC non functioning, but you still need the vacuum hose to be hooked up for the heater and vent doors to operate under the dash.

Here are the vacuum hose routing diagrama for a 74 Valiant A/C system:



The four diagrams show the flow of vacuum at different HVAC settings.

The large round black object you labelled "Vacuum port on vacuum (amplifier?)" is the vacuum reservoir depicted at the left of each diagram. The large port on it hooks up to the fitting on the intake manifold or some other strong source of vacuum. The smaller port (currently uncapped) goes into the firewall and provides vacuum for the rest of the HVAC hoses.

Starting from the vacuum reservoir, you are going to need to determine what hoses and parts are present and what hoses and parts are missing. Fortunately, the original hoses were color coded with a stripe on them, so you should be able to clean a section of hose off and see what color the stripe was and where it went.

If you don't have a factory service manual, you should get one. It will be invaluable for this project.

I am not sure what the round object on the firewall next to the OSAC valve was. Until you get the HVAC hoses all hooked up, you should cap the open fitting on the intake manifold. It make a big vacuum leak and might be why the motor is idling rough.

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Casually looking for a Clifford hyperpak intake for cheap.

i need one of those intake manifold vacuum "tap's." i have a 1985 Dodge D150 and two of the five "posts" are broken off, creating quite the vacuum leak... where might i find one? and do i need five openings? i dont have cruise control, so that removes the need for one. but i wouldn't mind running the ac/heater. any help would be appreciated!

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Thanks for your time!