Vacuum advance w/ solenoid

[tak419]

What exactly did the vacuum advance cans do that had the electric solenoid ? I read they retarded the timing under certain conditions. I have a distributor that has on one it and plugged it in and it advanced it some so I'm confused. Also read the 2 wire ones were wired into the idle solenoid, so where we're the single wire vacuum solenoids wired to ?

 

[wagonman]

Had a 70 Charger 383 HP with the one you are talking about. The wire went to the idle stop screw, there was a plastic bushing that insulated the wire so it only got ground when the throttle was closed. This was on the OEM Holley 600 the car came with. Pretty crude way to retard timing at idle only but it worked.

 

[tak419]

Found what I needed. The single wire distributor solenoid is spliced into the wire going to the starter so when you crank the engine the solenoid is also energized and advances the timing 6.5*. The 2 wire solenoid is energized the complete time the throttle is in the idle mode/ throttle lever resting on the idle solenoid on carb. As soon as throttle is lifted, the contact broke and timing goes back to unadvanced position.

 

[HALIFAXHOPS]

hm No it is for the HP B/RB motors for anti dieseling. It goes on and advances usually 5 degrees and stays there until the motor is turned off and then it retards 5 degrees along with shutting of the carb solenoid. Piece of crap system if you ask me. Think about it when you shut down there is no spark so why the advance retard. Expensive item to replace. Deal with them all the time. Diagram is for the two wire the one wire is basically wired the same.

 

[tak419]

hm No it is for the HP B/RB motors for anti dieseling. It goes on and advances usually 5 degrees and stays there until the motor is turned off and then it retards 5 degrees along with shutting of the carb solenoid. Piece of crap system if you ask me. Think about it when you shut down there is no spark so why the advance retard. Expensive item to replace. Deal with them all the time. Diagram is for the two wire the one wire is basically wired the same.
View attachment 757907

The 72 FSM shows the one wire and it is wired in to the lead going to the starter, so it is only on when cranking the engine. I agree, seems like a dumb system.

 

[HALIFAXHOPS]

Really? That is stupid advancing when hot starting is not usually not a good thing. I deal with 100 point guys on occasion and that whole system can get really expensive. NOS advances go from 150-350 depending on the application then the solenoids are 250-500 with the bracket and there are four different ones. And really hard to find used or NOS. I have a bunch of the advances used and a few nos. and out of say ten maybe you can make three. The box that goes on the two wire blow out. And the vac side is either blown out or the solenoid does not work, even the nos ones. I hate the dam things.

 

[tak419]

Yeah I was trying to figure the whole thing out cause I read it was a timing retard and that's what the manual says. I have a 71 and 72 manual. So my understanding according to the 71 manual, and by the way the box on the side of the 2 wire is suppose to keep the coil in the can from buying out lol. The 2 wire advances the timing anytime the key is on and the throttle idle solenoid is energized. When you give the car gas and lift the throttle lever off the idle solenoid, the ground is broke and the vacuum solenoid loses power and goes to normal timing. I guess it is called a retard solenoid because it keeps the timing advanced at idle. The one wire advances it only upon starting g the car because it's tied in with the starter wire. You're right, 5* on hot soak seems *** backwards but that's how it works. The factory also calls for 5-6* initial timing so may not be an issue. Set it to real world 12*+, lol good luck.

 

[72RoadrunnerGTX]

To be clear, the ’70-71, two wire, distributor vacuum advance/electrical retard unit, is designed to retard the timing about 5 degrees at curb idle. This is to reduce tail pipe emissions levels. There is no functional relationship to the idle stop solenoids other than an insulated cap on the idle solenoid plunger to activate (ground) the retard solenoid when the curb idle adjustment screw is resting on it.

The ’72 single wire distributor vacuum advance/electrical advance, as discussed, is designed to advance timing about 7.5 degrees while cranking only.

 

[HALIFAXHOPS]

To be clear, the ’70-71, two wire, distributor vacuum advance/electrical retard unit, is designed to retard the timing about 5 degrees at curb idle. This is to reduce tail pipe emissions levels. There is no functional relationship to the idle stop solenoids other than an insulated cap on the idle solenoid plunger to activate (ground) the retard solenoid when the curb idle adjustment screw is resting on it.

The ’72 single wire distributor vacuum advance/electrical advance, as discussed, is designed to advance timing about 7.5 degrees while cranking only.

Interesting. Is it in the FSM?

 

[72RoadrunnerGTX]

Page 9A-5, both '70 & 71 Plymouth FSMs. Page 8-47, '72 Plymouth FSM.

 

[HALIFAXHOPS]

I am not getting it? Looks to me it advances above 5.5. That I get not the retard

 

[tak419]

I had to read it twice to understand. On the 2 wire, the solenoid holds the timing retarded 5.5*. The service manual is saying when you disconnected the solenoid power the timing should go back to normal which would be and increase in timing and the higher rpms.

 

[HALIFAXHOPS]

Got it now makes sense since when powered it pushes the arm in which would be advanced and I am positive of that. Still a stupid design IMO They are usually bad.

 

[HALIFAXHOPS]

I now have to go look at my buddies six pack set up which is bone stock and see what it does. Confusing for sure.

 

[HALIFAXHOPS]

I had to read it twice to understand. On the 2 wire, the solenoid holds the timing retarded 5.5*. The service manual is saying when you disconnected the solenoid power the timing should go back to normal which would be and increase in timing and the higher rpms.

Just not making sense because the test cards have it as a 5 decreas in advance when powered. I know for a fact it does that when powered. he vac advance arm is out . Problem is there is no real description on this system. Wonder if there is a FSB on it?

 

[HALIFAXHOPS]

Found this in 1970 service highlights book I have

 

[tak419]

That was some good info . I wonder why they went to a single wire solenoid that advanced the timing just under starting conditions.

 

[HALIFAXHOPS]

I don't get it I would think it would kick back.

 

[mopar jack]

The electric vacuum solenoid was an attempt to reduce NOx emissions. At Idle the timing retards to 2- 2 1/2 degrees which raises combustion temp and lowering NOx. When applying the throttle the timing jumps up seven degrees added to the initial timing. In California back in the 70s and 80s we had smog testing and these cars would not make any power off the line when the solenoid failed. I bought a couple of big block cars that ran very poorly, couldn't bust a tire loose. I found the electric solenoid had failed so I set 10 dregees initial and those big blocks came to life.

 

[72RoadrunnerGTX]

The retard spec for that solenoid is 5 and half degrees (Service Procedures, page 9A-5, ’70 FSM). For ’70-71, the retard solenoid was a federal application, not just California spec cars. There were other add-on systems specifically targeting NOX for California spec cars that restricted vacuum advance under certain conditions, starting in ‘71.