What mods for my 904 when using the BPE 408?

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  1. Mopar Vince

    Mopar Vince FABO Gold Member FABO Gold Member

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    I will be replacing the tired, smokey, original 273 in my 1967 Barracuda #projectvertfish with a fresh BPE 408.
    Since it wont ship until mid October 2020, I have some time to freshen up, build up, and modify my 904 TF transmission to hopefully handle the 500-ish HP.
    What mods can you recommend and what torque converter should I get?
    Thanks in advance.

    20200323_115106.jpg
     
  2. Johnny Mac

    Johnny Mac www.blueprintengines.com FABO Vendor

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    Hey buddy, tagged you in our trans package post. Or, if you are going local rebuild, and sourcing your converter elsewhere, I have an ATI in mine. There are lots of good converter companies out there. Used Hughes in the past. I hear good things about PTC also. Usually get what ya pay for in a converter.
     
  3. rumblefish360

    rumblefish360 So close, yet so far away FABO Gold Member

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    What flex plate should be used? Neutral or weighted?
    Thanks
     
  4. Phreakish

    Phreakish Well-Known Member

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    • Johnny Mac

      Johnny Mac www.blueprintengines.com FABO Vendor

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      Assuming the converter is neutral, as most aftermarket ones are, then Yes, you use an LA 360 balanced flexplate.

      The Balancer (which we sell for under $90, and include on most dressed engines) uses the magnum weight for our engines)
      Mopar Small Block Harmonic Balancer | 273 | 318 | 340 | 360 | 408 |

      if its purchases on its own, it comes with various weights for all SB balances.
       
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      • kursplat

        kursplat FABO Gold Member FABO Gold Member

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        call Cope Racing and talk to John. i'm loving my new MRVB with the 273. planning to order the 408 from JM early next year. what gears are you running?
        also, don't know if your planning to stay full auto or not, but if not... -
         
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        • rumblefish360

          rumblefish360 So close, yet so far away FABO Gold Member

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          OK cool, so, IF I don’t have a flexplate, I use a B&M 360 flexplate designer for neutral balance converters.
          Correct? And a front harmonic balancer like yours or one for the listed years on the Blue Print site.
           
        • Johnny Mac

          Johnny Mac www.blueprintengines.com FABO Vendor

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          You got it!!!!

          Both of our current 408 engines need the magnum weighted damper. thats as of today. the 4085 and 4082 based PN's

          For the flexplate 95% of the time, you order one for a LA360 balanced engine. BECAUSE most aftermarket torque converter are neutral. so the imbalance is made up at the flexplate.

          Chrysler in their infinite wisdom from the factory, used NON weighted flexplates, and put the weight on the converter. not many aftermarket companies weight the converter. but i have seen it.

          so the only reason to buy a neutral flexplate for our 408, is if your converter was built with the weight on it. which is rare....or stock....and stock doesn't jive well with a cam anyways.
           
          Last edited: Oct 22, 2020
        • Mopar Vince

          Mopar Vince FABO Gold Member FABO Gold Member

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          • rumblefish360

            rumblefish360 So close, yet so far away FABO Gold Member

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            @Mopar Vince It is in my opinion that the 904 will serve you well without issues while allowing more HP & Tq. to the wheels since it takes less lower to turn. The lighter weight is also a plus.
             
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            • kursplat

              kursplat FABO Gold Member FABO Gold Member

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              and a little more room to hook things up is nice too. what gears in the rear?
               
            • Mopar Vince

              Mopar Vince FABO Gold Member FABO Gold Member

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              It has the super rare, a-body 8.75 with a 3.23 sure grip center section. It originally had a 7.25 peg-leg. I was lucky enough to pick one up for just $550 from a local Mopar guy. He even threw in a just right rear disc kit with it and a set of large bolt pattern Yukon axles.

              20200202_153139.jpg
               
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              • Krooser

                Krooser Reform School Graduate

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                A 904 will suit you well.
                 
              • oldkimmer

                oldkimmer FABO Gold Member FABO Gold Member

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                Am I reading this right? A Magnum weighted dampner and a LA weighted flexplate. Kim. @Johnny Mac
                 
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                • Mopar Vince

                  Mopar Vince FABO Gold Member FABO Gold Member

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                • Johnny Mac

                  Johnny Mac www.blueprintengines.com FABO Vendor

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                  For all.
                  Trans i recommend(same 30 month warranty as the engine)
                  MOPAR SB 727 PACKAGE | 3 SPEED AUTO KIT FOR SB MOPAR | 2200-2600 STALL CONVERTER

                  Damper I recommend (magnum weight)
                  Mopar Small Block Harmonic Balancer | 273 | 318 | 340 | 360 | 408 |

                  And a LA 360 flexplate, assuming you have an aftermarket, non weighted, converter.

                  We DO sell complete engine/trans packages
                  And we can work together on options

                  BLUEPRINT ENGINES BUILDER SERIES Mopar 408CI Stroker Crate Engine and 727 Auto Transmission | Small Block Chrysler | Roller Cam | Polished Front Accessory Drive
                   
                • Johnny Mac

                  Johnny Mac www.blueprintengines.com FABO Vendor

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                  Correct, the assemblies balance best with the la 360 flexplate, and mag 360 damper.

                  Most of our aluminum headed engines ship with with damper pre installed.
                   
                • oldkimmer

                  oldkimmer FABO Gold Member FABO Gold Member

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                  So is this a magnum or LA engine? Or do they all balance like that? Kim
                   
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                  • 66fyssh

                    66fyssh Don't Stop Believin' FABO Gold Member

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                    Agree Kim, I'm confused.
                     
                  • Johnny Mac

                    Johnny Mac www.blueprintengines.com FABO Vendor

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                    @oldkimmer @66fyssh
                    Its a Magnum block. It can easily bolt in place of any LA engine.

                    A. It uses a Magnum weighted damper
                    B. It uses an LA 360 flexplate / flywheel.

                    Its an aftermarket rotating assembly, it requires less weight to balance than a stock 360, so the nose gets the slightly smaller, Magnum weight when we spin it up and balance it.

                    Any confusion is kind of a mute point as the aluminum headed engines come with the proper damper already on them, and we sell the damper outright also.
                     
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                    • oldkimmer

                      oldkimmer FABO Gold Member FABO Gold Member

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                      I would then think it would be a good idea to include the dampner and flex plate so there would be no balance issues for no one. Just my observation. Kim
                       
                    • Johnny Mac

                      Johnny Mac www.blueprintengines.com FABO Vendor

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                      Damper is included on most configurations. Shouldn't be any issues for those that read the included documentation, or look at our website.
                       
                    • oldkimmer

                      oldkimmer FABO Gold Member FABO Gold Member

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                      Thanks
                       
                    • 12many

                      12many If I Only Had The Cash.......

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                      One thing not often mentioned about flex plates is the fact that the B&M flex plate (or other race HD style) is a much thicker and more rigid type vs. the oem style that actually flexes. It’s less forgiving/ doesn’t really flex compared to the oem. If the block has ever been line bored you might run into a scenario where the crank is on a different centerline than the trans input shaft and pump hub bushing etc and the converter being on a less flexing plate could wear the bushing in the pump, possibly more so than using oem. Just something to consider when deciding going with an oem or more race oriented piece that would require checking things and possibly using offset dowels on the block.
                       
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