advance springs

Slant 6 Engines

  1. volaredon

    volaredon Well-Known Member

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    what advance springs work on a /6? I have a distributor that I want to go thru for my fresh engine. I forget the tag number. It's the common one they used on the Super 6 engines, late 70s. not sure what the advance curve, etc is now but Im sure it's as made by the Mopar factory back in the day.

    UPDATE; PN is 3874876

    Plans are to dismantle, put any metal parts in the ultrasonic and make sure they are clean as can be, lube up the advance weights, and reassemble with new parts listed below, that I already have on hand.
    I'm looking for some of the "lightweight" springs that were being sold a while back by a guy on the forums.
    will the Moroso or Mr Gasket ones work on our engines? hopefully I don't have to have a pile of /6 core distributors to rob them from.
    I have an iron gear, new NOS electronic pickup, and new advance can already, for this dist core that I have.
     
    Last edited: Jun 26, 2021
  2. Early a body

    Early a body Well-Known Member

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    use one of the mr gasket advance springs, replace the larger heavier spring. if you replace both the timing will possibly bounce at idle and advance too quick. i have them in a slant 6 with a little hotter cam and 4 barrel. one spring is all you need.

    For even more fun, purchase the advance plate sold by 4 seconds flat.com and then you can increase your initial timing to 10 or so and get better throttle response from a stop.
     
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    • volaredon

      volaredon Well-Known Member

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      So you're saying to remove both springs and only put it back together with a spring only on 1 side? That don't sound right
       
    • krazykuda

      krazykuda Well-Known Member FABO Gold Member How-To Section Editor

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      • Early a body

        Early a body Well-Known Member

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        no no , sorry for confusion. you need both springs. Just remove the heavier spring from the distrib and replace with one from the mr gasket kit( both springs in the mr gasket kit are the same) Doing so will allow the advance to come in quicker. And like I said you will have more of a noticeable off the line quickness if you adjust the initial timing higher. I have mine at 10 degrees. But not past 32 degrees total timing on a slant six.
         
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        • toolmanmike

          toolmanmike Moderator Staff Member FABO Gold Member

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          This^^^^^^^^^^^^^^^^^^^^^
           
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          • halifaxhops

            halifaxhops It's going to get stupid around here! FABO Gold Member

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            You really have to figure out what are in the distributor now and adjust the curve as needed The Mr. G and MP springs come in seriously fast and allso make sure when it is apart the upper shaft is straight.
             
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            • kesteb

              kesteb Well-Known Member

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              If you have a real F-Body SuperSix distributor it should have the 9R governor. This will limit advance to 18* total. This will allow you to sit initial to 12* BTDC. I believe the guy on .org is still selling his spring kit. His kit includes a crude chart on how the springs works.

              Now it is trial and error to figure out what works for your combination. I suggest a dial-back timing light and a chart to map how the spring set works for your combination.
               
            • halifaxhops

              halifaxhops It's going to get stupid around here! FABO Gold Member

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              Agreed. Dont 100% trust a dial back unless it is digital. Try to use a timing tape. Those style lights are known to be wrong/off.
               
            • volaredon

              volaredon Well-Known Member

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              I have an NOS distributor in the engine that is in the truck right now. Found it on ebay a year ago. Came to me in a genuine Mopar parts box with an old "from that day" parts logo tag on it.

              I only have like 100 miles on it since I did the lean burn ectomy on it, and completely redid the underhood wiring harness due to past owner butchery.
              I want to put that one in my new motor when I swap it out. But I want to rework it first, to better suit my engine as built, and considering that it's in a truck. I also have a good used core here to rebuild, And for that core I have the new parts I listed in an above post. The distributor gear I have here is a Echlin DG404, old stock, cast iron.... now a days, all that can be had (even by that same PN and from Napa) is nylon. I'd like to find at least 2 more cast iron ones.one for the NOS distributor, one for for my core, and one for the slant in my kid's truck.
              In past years I've had problems of the nylon ones breaking. Not often but I've had a few.
              Both my nos one and my core that I want to rebuild are Mopar PN 3874876. Which I think is the super six unit.
              I haven't done anything with the nos one except to drop it into my engine and run it,
              though guys on the /6 .org site had said it "should" have a vac advance can with "11.5" on the arm, but they gave me a part number for a STANDARD brand advance can with an "8.5" on the arm since I am using this engine in a truck instead of a light A body.sound right? Or not?
              What difference would an advance can with "11.5" on the arm change vs one marked "8.5"?

              I have 2 of the recommended advance cans here/one for the nos distributor and one for the spare I am building up. But have not yet put them in.
              Regarding advance cans: on the ones that are adjustable, what does playing with the Allen head screw in the vac nipple actually change?
              Is it the range where vac advance starts and stops, (by amount of vacuum applied, I'd guess), or is it the total amount of vac advance that can will provide, or something else?
               
              Last edited: Jun 26, 2021
            • volaredon

              volaredon Well-Known Member

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              Also, given my combo isn't stock, how will that alter how I'm gonna want to set it up?
              This is going onto an 85 d150 long bed, with a 727 and 3.21 rear gear. Projected usage is mostly a daily driver, with occasional usage as the truck that it is including towing a light popup a few times a year. Elevation from sea level/ whatever Chicago is. I think we're around 500 ft above sea level.

              Most of it will be as a stock super six, biggest change will be a reground #819 cam from Oregon cams. I did shave the block and head a total of 0.100"
              But even with all that metal removed from the block and head, given that the head gasket I have is triple the thickness of the original steel shim head gasket, (the Aussie one) net change will be 0.060" tighter than original. Which sounds like alot, but according to calculations, when measured out, head cc'd and piston in the hole dimension figured in, I'll only be a tenth of a point or 2, of compression ratio, over advertised stock CR for the '74 slant 6, that it is. If the edges of the combustion chamber diameter shrinks a little where I can use a more conventional fel pro,etc head gasket at 0.040" (still 2x the thickness of the steel shim gasket that was original) I'm gonna be about 8.8-8.9:1.
              So given that, what amount of initial, mechanical, and vacuum advance and at what rpms should I be shooting for?
               
            • volaredon

              volaredon Well-Known Member

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              @RustyRatRod @halifaxhops @halfafish
              @68 barracuda thoughts on this?I have a digital dial back style timing light here already as was suggested above.
              I haven't looked lately / but if I remember right,
              "Halfafish" was in on the distributor rebuild article on the other site.
               
              Last edited: Jun 26, 2021
            • volaredon

              volaredon Well-Known Member

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              your link doesn't take anyone to where you intended though I found them. On this limiter plate, all I saw listed was for V8 engines. Would the /6 and V8s take the same plate? I thought the /6 dist body was slightly smaller dia.
               
            • halfafish

              halfafish Damn those rabbits, and their holes! FABO Gold Member

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              True, I am listed on the distributor rebuild article on slantsix.org but I don't deserve any credit as I didn't write anything for the article. I took the photos, recorded the information on how to do the rebuild, transcribed the recordings, and put the article together. The author of the article and the guy that knows how to do this is dusteridiot. I was just the goon with the camera and voice recorder who put it all into a workable format.
               
            • RustyRatRod

              RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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              If you really want to mess around with it, get the FBO limiter plate kit with the sprAngs from Don Gould. A lot of times in the past, I've had good luck with one light sprAng and one medium SprAng. Two lights are too light and can sometimes have some mechanical advance at idle. Two mediums are sometimes too heavy and don't allow total timing until 3K or more and that's a little late.....unless you have some compression.
               
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              • volaredon

                volaredon Well-Known Member

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                Don Gould? Huh?
                 
              • Bugman

                Bugman Well-Known Member

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                [/QUOTE]
                There used to be 3 different vacuum advance cans. One marked 11 gave 22 degrees of advance,this one came stock in 3874876 distributor. So 3874876 with 12 degree base timing and 10 degrees centrifugal advance at 2000 rpm with 22 degree vacuum can ,result would be 44 degrees. Swap can to one marked 8.5 -17 degrees result 39 degrees. Can marked 7 -14 found in trucks,result 36 degrees
                 
              • kesteb

                kesteb Well-Known Member

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                The timing requirements for a lightly loaded as compared to heavily loaded d100 will be different. I would talk to dusteridiot on .org for advice.

                If you really want to micro tune the ignition, I would suggest investigating a EDIS/MegaJolt setup. The same thing can be done with a Micosquirt and LSX coils. This would give you a fully programmable crank triggered ignition.
                 
              • Early a body

                Early a body Well-Known Member

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                Yes its the same for both engines. I have one in my slant 6 I put one of my dad's many slant 6s to convince him cause he is very old school and he was impressed on how easy it is to install too.
                 
              • Bewy

                Bewy Well-Known Member

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                6 crank degrees difference between the 8.5 & 11.5* cans. If 6* more advance with the 11.5 unit is going to cause a problem, it will probably manifest itself as surging at light cruise speeds. The factory has to be conservative with settings so the engine may well tolerate the extra timing, with a little extra fuel economy as a bonus.
                 
              • volaredon

                volaredon Well-Known Member

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                not looking to get that crazy. 90% of the time I'd say "lightly loaded". maybe 95%.
                want to stay mechanical, carb'd. yeah, I know you can get crazy adding electronics into the mess, but not interested. Electrical/electronics isn't my cup of tea.
                Working on much newer vehicles at work, I get hung up too often as is, when all this electronic wizardry goes nuts. This truck is all about K.I.S.S. (keep it simple, stupid) trying to stay as far away as possible from "check engine" lights, a ton of sensors, codes, and such. All while making it "the best it can be for what it is". add in the "hey, look what I did" thing.

                there is a certain umm, I dunno what to call it, satisfying feeling in mechanical controlled repeatability without bad grounds, smoked sensors, corroded wires, don't need a scanner or other computer type device to figure out what's wrong with a truck. and mechanical settings can be changed easier (for me anyways) than electronic ones.
                Plus I'd rather be closer to being able to fix any problem that might show up "with a screwdriver" than a scanner, laptop, a pile of schematics, etc.
                 
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