Low signal vacuum can availability?

[hunt2elk]

I have my newly rebuilt 451 running pretty good, but am fighting with dieseling/run on when the key is turned off. Running a Firecore distributor set at 18 initial and 34 total, 46 all in with the vac can hooked to ported. I want to try stabbing it on manifold, but am having an issue with only 7.5" idle vacuum. It cruises at 2500-3000 rpm at 16-17". With the screw turned in all the way to weaken the spring, it will just start to activate at 7" or so. I need a can that will be pulled in at 5 or 6 inches. The Firecore distributors are supposed to use the stock Mopar/Mallery style cans. I can't find anything that would work in this situation. Any ideas?
I just went through this on my 493. That motor makes 15" of vacuum at idle though. I have a MSD dist on that car and was able to buy a can that works perfect. It adds 10 degrees at idle, allowing me to shut down my idle speed screw enough to eliminate the dieseling.

 

[Geoff 2]

You are on the right path. Not sure what Mopar Adj VA units limits are; maybe try Hughes or Mancini.

 

[F4R/T]

I’d try Ray @HALIFAXHOPS

 

[HALIFAXHOPS]

Most are adjustable for when they start to operate by rate. Not how far they advance funny just hit this on FABO. it does is adjust the rate of advance by how much it advances by vacuum not total amount of advance. To make it easy say the arm has 10 stamped on it that is the max amount of distributor degrees you can achieve. Say you want that at 51nhg then crank the screw clockwise most of the way. You want it to come in at 10 inhg counter clockwise the screw untill the result is achieved. now to lock it out USUALLY just turn it all the way counte clockwise and it wil compress the rate spring al the way down in effect locking it out. Hope it helps.
This shows how

 

[hunt2elk]

Most are adjustable for when they start to operate by rate. Not how far they advance funny just hit this on FABO. it does is adjust the rate of advance by how much it advances by vacuum not total amount of advance. To make it easy say the arm has 10 stamped on it that is the max amount of distributor degrees you can achieve. Say you want that at 51nhg then crank the screw clockwise most of the way. You want it to come in at 10 inhg counter clockwise the screw untill the result is achieved. now to lock it out USUALLY just turn it all the way counte clockwise and it wil compress the rate spring al the way down in effect locking it out. Hope it helps.
This shows

Here is what the can looks like. Would you have one that moves the arm at a lower vacuum signal. I'm not concerned with how much it moves as I can limit the travel with a shim of some sort.

 

[HALIFAXHOPS]

Just adjust that one read above. They ALL HAVE TO BE SET!!!!!! You might have to try a few different stamped amounts to get it that low. I never had to set them there at all. I always run ported only like a mopar should usually have.

 

[hunt2elk]

Just adjust that one read above. They ALL HAVE TO BE SET!!!!!!

Yes, I know that. My issue is that this motor has low idle vacuum, so I need a can that with spring pressure that starts moving earlier than the normal stock can does. In a perfect world, I want one that is fully deployed around 5".

 

[HALIFAXHOPS]

Pulle in arm at 5inhg? As in say ten dist degrees?

 

[HALIFAXHOPS]

Not sure if they make one that way I have hearsd of people using stock vacuum amplifiers to do it on some GM. Why not a idle solenoid?

 

[HALIFAXHOPS]

Mopar had a set up think 70-73 stupid as hell. Had a sol on the vac advance to retard the timing 5 degrees and to a solenoid on the carb. Turn the ignition off I get the solenoid on the carb closes the primary ventury to definately stop dieseling, but also retard the timing 5 degrees. Why there is no spark with the key off and has nothing to do with dieseling. Super expensive now. EPA thing.

 

[hunt2elk]

Pulle in arm at 5inhg? As in say ten dist degrees?

Yes and yes.

 

[Geoff 2]

Below is the chart for the Accel adj VA units for GM dists. Not sure if Accel made one for Chrys.

 

[HALIFAXHOPS]

I have to ask this is there any vacuum at all even a lb at the ported vac at idle?

 

[hunt2elk]

I have to ask this is there any vacuum at all even a lb at the ported vac at idle?

No, nothing at all.

 

[HALIFAXHOPS]

Have a minute to call me?

 

[hunt2elk]

Below is the chart for the Accel adj VA units for GM dists. Not sure if Accel made one for Chrys.

View attachment 1485061

I'm fairly certain that is the can I bought for my other car. It fits Chevy and MSD distributors. They don't make one for Chrysler however.

 

[Geoff 2]

Yes, & if I remember correctly, there is a 'surprise' in store for those using the Accel or Crane adj units.
There is a spacer inside the spring that limits spring adjustment, the thing locks up. In the past, I have prised the can open & removed the spacer.
Now, I can buy a new HEI with adj MVA unit for under $100; no spacer in the VA unit.