Re: {Chrysler 300} vacuum advance / discussion , 300J

[John Grady <jkg@xxxxxxxxxxxxxxxxx>]

thank you Carl , great suggestion . Bought one , will let you know how it works out 
Spendy —But Would spend  more than the the 120  $ in time messing with old one … 

> On Feb 6, 2026, at 6:14 PM, Carl Bilter <cbilter@xxxxxxxxx> wrote:
> 
> Van's Auto has a reproduction 62-69 big block dual point vacuum advance canister that might work.  Might not be exactly correct advance, but better than non-functional.
> 
> Carl B.
> 
> https://vansauto.com/product/back-lenses-66-67-charger/
> 
> 
> ------ Original Message ------
> From "John Grady" <jkg@xxxxxxxxxxxxxxxxx>
> To "club chrysler" <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
> Date 2/6/2026 11:48:53 AM
> Subject {Chrysler 300} vacuum advance / discussion , 300J
> 
>> So , rebuilding a J distributor , vacuum can arm is stamped 8 (on arm) i recall from somewhere that those numbers are 1/2 the max vac advance you get out of  that can . so 16 degrees ,
>> The can leaks vacuum . Most of them do over 25 years old or so
>> I had same issue a few  years back with a 37 packard 6 . NOS no good will soon crack too . Took apart , kind of rubberized canvas
>> Both J and packard are unobtanium.
>> Can was crimped all around , tried that way in, on packard   mixed review ; problem is not the edge (grind off ,  can use 2/56 screws) but attaching the arm to the center.
>> I see rebuild services, but want 200 up ..  not sure what you get either
>> Thinking about this , the force that a diaphragm can make has nothing to do with the material ( if flexible enough , i had silicone rubber sheets ) —   it only has to do with area of it and max of 14 psi vacuum . … so the  curve or rate of advance is therefore set by spring and sometimes  shim washers under    the spring ( not first rodeo with these )
>> The total amount is set by a projection on the arm stamping that hits the can mount after certain inward travel , fortunately all that is outside and at  “full out extension” sitting on bench , you can measure, projection to can  and add shim to stop / match say the 8 .
>> So it would seem if you get a new can , that physically   fits our distributor , you can stop it at 8 ok , ( it is usually more than that ) and by transferring J spring / shims on it , you should have a J advance  set up ?
>> Looked at this with packard and a few Mopar 300 distributors ( A block /392) a few years back , bought a mid  60’s  very common 318 dodge vacuum unit , widely used for ten years seemed close enough  , but had not thought of stop idea at that time , moved more than 8
>> So thinking some late 60’s b block advance, before pollution stuff  , might be a good source for a can for B block 300 .
>> Complicating this  is our cars have the cast iron dual point , For B block, a rare bird , not sure if mechanically the same fit as lower end aluminum body single point as far as vacuum can .
>> On A block i was able to rebend the arm offset and drill new pivot hole , as height of offset was different,
>> All seemed to work ok   on that one and also on packard , but ended up with a 1950 nos , tried and it fit the 37 - on that one . It was a six , degrees will change per mm moved maybe , maybe not ,( pondered that, how far is pivot from center?  )  but easiest  way out  on that . Did not leak
>> Wonder what others think or do on this ? check yours , mity vac , if not working gas mileage drops way down  .. worth 4-5 mpg on 392 ..
>> 
>> .
>> 
>> 
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