Can I get a NEW distributor vacuum advance module?

[timk225]

I tested the vacuum advance module when I got my Duster almost 2 years ago, and it seemed okay, but it is an old part with old rubber in it. And the car normally gets around 14 mpg even with highway gears and not being run hard excessively. So for maintenance and troubleshooting, I'd like to get a new or rebuilt vacuum advance module for the Slant 6 distributor. Does anyone know where I can find that?

 

[Demonic]

Rock Auto, amongst others:

More Information for STANDARD MOTOR PRODUCTS VC184

 

[mbaird]

1971 DODGE DART 3.7L 225cid L6 Distributor Vacuum Advance | Shop Now at RockAuto

Check for specific applications.
They vary by amount of advance and vacuum parameters for various car/engines.

 

[timk225]

I checked the rock auto parts list for a 1973 Duster with a 1 bbl 225, and both the manual and automatic versions were stamped 8.5R on the advance arm.

 

[mbaird]

What amount of advance would be right for a '73 Duster 1 bbl Slant 6 with automatic transmission? I see those 3 are stamped 9.5, 6.5, and 9.5 on the arm.

I don’t know slants but the numbers are the amount of distributor advance . Double that to get crankshaft advance .
Do you have a 73 service manual? They have that info . Assuming your engine is stock .

 

[halifaxhops]

I haveNOS, NORS and rebuilt if needed. Most slants are marked 6.5R

 

[volaredon]

I've seen 8.5R and 11R on /6 distributors I've worked on "in the field" I believe there are also some marked 6.5 and 9.5R.
I've bought a handful of them on eBay. All the old tried and true ignition brands are available if you look. I THINK (don't remember for sure) that the ones for a small block are the same
And yes there are several arm markings available.

 

[halifaxhops]

The fsm will tell you what you need. They have been changed so often they cant be trusted as they sit in the dist anymore.

 

[halifaxhops]

I've seen 8.5R and 11R on /6 distributors I've worked on "in the field" I believe there are also some marked 6.5 and 9.5R.
I've bought a handful of them on eBay. All the old tried and true ignition brands are available if you look. I THINK (don't remember for sure) that the ones for a small block are the same
And yes there are several arm markings available.

LA and slant electronic have the same arm. Polints are more straight arm if this helps. These are BB

 

[xLURKxDOGx]

I tested the vacuum advance module when I got my Duster almost 2 years ago, and it seemed okay, but it is an old part with old rubber in it. And the car normally gets around 14 mpg even with highway gears and not being run hard excessively. So for maintenance and troubleshooting, I'd like to get a new or rebuilt vacuum advance module for the Slant 6 distributor. Does anyone know where I can find that?

Try local, I got the correct one for mine from Oreileys A month or so ago.

 

[Mattax]

It's the original distributor for a '73 225
But there's been some changes to the engine.

@timk225
You can but is there any reason to think the vac advance is not working?
A vac gage and or Mightyvac is well worth cost if you don't have yet.

Did you ever measure the timing vs rpm?

For highway mpg, have you tried leaner main jets?

In my experience with a '75 fully smogged 4 door, 16 mpg in mixed driving is typical. With a '68 Barrcauda notchback, the 225 got over 20 mpg on the highway. Not enough local driving with it to have reliable mixed driving mpg.

T

Post in thread 'Optimize the spark curve for a SlantSix.'

Sep 9, 2025

The distributor tag number is 3755042. There's also a 50 and a 2 on the tag. Vacuum advance was ok. I've since changed the carburetor to a 350 Holley 2 bbl, it'll idle slowly now. I have a tach in the car. I'll have to check the timing and see what the numbers I get are.

No I didn't use a piston stop to verify the timing mark is accurate.

• timk225

 

[timk225]

It's the original distributor for a '73 225
But there's been some changes to the engine.

@timk225
You can but is there any reason to think the vac advance is not working?
A vac gage and or Mightyvac is well worth cost if you don't have yet.

Did you ever measure the timing vs rpm?

For highway mpg, have you tried leaner main jets?

In my experience with a '75 fully smogged 4 door, 16 mpg in mixed driving is typical. With a '68 Barrcauda notchback, the 225 got over 20 mpg on the highway. Not enough local driving with it to have reliable mixed driving mpg.

T

Post in thread 'Optimize the spark curve for a SlantSix.'

Sep 9, 2025

The distributor tag number is 3755042. There's also a 50 and a 2 on the tag. Vacuum advance was ok. I've since changed the carburetor to a 350 Holley 2 bbl, it'll idle slowly now. I have a tach in the car. I'll have to check the timing and see what the numbers I get are.

No I didn't use a piston stop to verify the timing mark is accurate.

• timk225

Since I made that above post, I had done a job to change the intake valve stem seals, the old ones were in bad shape, and that seemed to help the spark knock problem some. At that time, I got a piston stop and tried it at several settings, the timing mark on the balancer was within a degree of accurate. If I remember correctly, the 350 Holley I have on the car now has #63 jets in it. Those are what it came with.

 

[volaredon]

If I do intake seals I also do the exhaust side or I don't do any.

 

[Mattax]

Since I made that above post, I had done a job to change the intake valve stem seals, the old ones were in bad shape, and that seemed to help the spark knock problem some. At that time, I got a piston stop and tried it at several settings, the timing mark on the balancer was within a degree of accurate. If I remember correctly, the 350 Holley I have on the car now has #63 jets in it. Those are what it came with.

yes oil and carbon can contribute to knock or pinging.

Post 11 of that thread you wrote that the Holley has a #63 jets.

If you're want to chase milage or performance that is one of the things to experiment with.

However the first thing to do is get base timing correct. Buy or make a timing tape and find a tachometer.
I wouldn't change any parts unless there was a specific reason. A vacuum gage or a mity vac will show if the vacuum has failed.

I posted the factory specs for that distributor, and assuming its working OK, the initial timing will have to be very close to the factory specs. For what your doing, a distributor curve similar to what was used in the 60s before emissions, or later with cats would be best.
However, a work around may be to set the initial at factory spec, which is like TDC at 700 rpm, and then connect the vacuum advance to a manifold vacuum source.

You have the timing light. Get a tach. And if need be a vacuum tee. When the distributor is connected to the manifold vacuum source, the timing should jump up. Then you don't even need a vacuum gage or mity-vac

 

[Jim Kueneman]

Get the NOS one. I have fought with several aftermarket pieces of crap. They would catch and stick when the vacuum released it so all the engine did was backfire as it was WAY to advanced under load.

Jim