5.7 Hemi Engine swap on 70 RR (Project)

New Hemi Engine Swap

  1. 5.7 hemi

    5.7 hemi FBBO Gold Member FBBO Gold Member

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    Running a dead head system? The Gen 3’s need 58psi.
     
  2. Mark Robinson

    Mark Robinson Well-Known Member

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    Tachometer issues;
    Got my fuel issues solved and car is running good. I haven't had much time to work on the RR in a while but tinker when I can. One problem I've run into is my "tic toc" tach. not working and need some help deciding what to do before I throw parts at it. I bought a digital conversion board from "Real Time Engineering", https://www.rt-eng.com/index.php/RTE_67-74_Tach_kit.html This replaces the old analog board (which was fried) to a digital board. It wasn't a piece of cake to install but not bad. Problem is my tach. isn't working. I took the dash panel out again and check everything - seem to be good but tach only flutters when engine is running.
    I went back to my engine installation manual and they talk about providing a tach loop with the crate motor wiring harness - which is what I hooked into. The manual also says "The tachometer loop is provided for the user to add an aftermarket tachometer that is made for multiple ignition coils. It does not supply a standard tachometer signal". Bingo. So I call Realtime and told them my problem and ask for suggestions - "Our board was designed to work with the following;
    1. Points
    2. Electronic Mopar Ignition
    3. MSD electronic ignition using the "tach" output from the MSD box (This is a 12V square wave)
    4. Pertronix electronic ignition module.
    We have no knowledge of the multiple coils type tach signal."
    Ok, so the board is providing a "12V square wave" and the tach loop is providing a multi coil signal.

    tach1.JPG

    Their has to be some conversion and someone on this forum must of run into this.
    I found some stuff on Summit;
    https://www.summitracing.com/parts/msd-8920?rrec=true
    https://www.summitracing.com/parts/msd-8918?rrec=true
    https://www.summitracing.com/parts/atm-9117?rrec=true
    https://www.summitracing.com/parts/dak-sgi-8e?rrec=true
     
  3. 5.7 hemi

    5.7 hemi FBBO Gold Member FBBO Gold Member

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    MSD makes a tach adapter for the Gen 3’s. It taps off the #7 coil wire(forget which color) and then you can hook you tach to the wire off the MSD.
     
  4. Mark Robinson

    Mark Robinson Well-Known Member

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    Thanks for your suggestion 5.7. I'am looking at the MSD stuff and there is a bunch. Do you happen to know the number of the tach adapter you have had experience with?
     
  5. 5.7 hemi

    5.7 hemi FBBO Gold Member FBBO Gold Member

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    MSD has 2 of them, I forget which one I used, also my dad had to use 1 for his FAST EZ EFI conversion. I do know one of them is list for the Gen3 Hemi swaps.
     
  6. Mark Robinson

    Mark Robinson Well-Known Member

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    Well the tach. is still an issue and sometimes you need to move on to get away from frustrations. So I moved on to my alternator problem, now on my third alternator (thanks goodness for warranties). The new alternators are controlled by the PCM and as soon as I would plug my field (PCM) wires to the alternator you could smell it smoking. Have the main wire going to the starter which is linked to the starter relay which goes to the battery. The gremblems from the old to the new are coming out on this car. It's really neat to have everything power but the old systems weren't designed to handle the power fans, AC, computers, all driven by a 160 amp alternator. - and everything was running through my amp meter which was designed for about 60 amps. More than my alternator was melting - my bulkhead connects were frying and the wires were melting. Good new is I think it is savable. First I need to bypass the amp meter (wanted to keep the dash original - not happening). There is a blog that tell you how to bypass the amp meter;
    https://www.forbbodiesonly.com/moparforum/threads/bulk-head-connectors.177313/
    http://www.madelectrical.com/electricaltech/amp-gauges2.shtml
    I have it about half done - I think this may solve a lot of problems, especially future ones.
    From one frustration to another, but I love it....
     
  7. Jeff Brundage

    Jeff Brundage FBBO Gold Member FBBO Gold Member

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    I used the Dakota Digital adaptor for my 6.4 hemi swap. You can set it to work on a bunch of different outputs and inputs. SGI-8
     
  8. Jeff Brundage

    Jeff Brundage FBBO Gold Member FBBO Gold Member

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    I know it’s a big expense but git rid of the old wiring harness. If you have melted some wires that you can see, you probably have some melted you can’t see. All that old wiring is going to give you grief once you start driving it. At the very minimum carry a fire extinguisher!
     
  9. Mark Robinson

    Mark Robinson Well-Known Member

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    First, I called Dakota and talked to their tech support. They don't know if their SGI-8 will do the conversion - they need to know what there products does! Still investigating but thanks for your input Jeff. Question, does the wiring harness on your 6.4 provide a tach. loop?
    Second, I think a fire extinguisher is a good idea in any of these cars - the design is bad. But I think getting rid of the amp meter is definitely a good idea. I hate the idea of adding aftermarket gauges, but the stock ones really do suck. I'll take some pictures of my damage and doing the conversion - will update shortly.
     
  10. Mark Robinson

    Mark Robinson Well-Known Member

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    Ok so I bypass the amp meter and followed the directions given previously, some pictures;

    Hard to see but wires starting to burn inside the firewall

    IMG_5686.JPG


    Things were getting toasty - top 4 and bottom 2 are the same circuit. Goes in from the alternator and comes out using fuse-able link to starter relay.
    IMG_5706.JPG

    Drilled out the upper right on the top connector. These two are used for ac and are not going to be used for anything. Could of used the damaged ones but figured they had enough.
    IMG_5707.JPG
    Pretty simple, just used a drill bit and drilled through the firewall. Took out the gauge cluster and eliminated the amp meter by taking off the wires and connecting them together. I used a fuse here - know it's overkill but some added protection.

    IMG_5692.JPG IMG_5693.JPG IMG_5694.JPG IMG_5695.JPG

    I then connected the two wire going through the bulkhead to the damaged wire on the inside of the firewall.

    IMG_5705.JPG

    Finally I connected the black to the alternator and the red to the starter relay using another fused link.

    IMG_5708.JPG

    Now I need to reinstall my gauge cluster, but I think I will attempt to convert my amp meter to a volt meter following a person that has done it on a non rally dash. Just trying not to add gauges to the bottom of the dash. Will let you know how that works.
     
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    • Jeff Brundage

      Jeff Brundage FBBO Gold Member FBBO Gold Member

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      Yes I had a tach output on the harness i got from hotwire
       
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