5.7 Hemi install question

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    Author Topic: 5.7 Hemi install question  (Read 4631 times)

    Offline MEH

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    5.7 Hemi install question
    « on: July 26, 2013 - 11:26:28 PM »
    I have installed a 2004 5.7 Hemi and 545RFE tranny in my 1974 Cuda. I have the car running. I have a separate switch for power to the computer. Has anyone been able to figure out how to wiring the computer into the car harness to have a constant power supply to the computer when the ignition is turned to either the start or on position. I assume this could be accomplished with relays. Please let me know if anyone has had success with this!!! Also has anyone used a newer style power brake booster and master cylinder in their resto rod??
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    Offline Chryco Psycho

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    • 70 Challenger R/T SE 70 tube Chassis Cuda now sold
    Re: 5.7 Hemi install question
    « Reply #1 on: July 27, 2013 - 07:08:30 AM »
    you could also tap into the brown dtart & blue run wires & use a simple diode to prevent backfeed . but a relay system would work as well . you have the wiring for the ballast near the wipwer motor or under dash at the column , MSD just uses a pig tal to connect both together with no issues if it works for the MSD it should work for the computer as well
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    Offline thedodgeboys

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    Re: 5.7 Hemi install question
    « Reply #2 on: July 27, 2013 - 07:49:05 AM »
    This may help, it what I did for my 70
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    Go Fast & Have Fun...
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    Offline PlumCrazyChris

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    Re: 5.7 Hemi install question
    « Reply #3 on: July 31, 2013 - 06:45:36 PM »
    I just got my started and am having the same issue.  You have to turn the key "on", then push a button to get it to crank and start.  There has to be a solution to this. 

    Thanks a nice post dodgeboy, but I don't follow it. 

    I'm just tapping into the wires for the computer.  I thought I could just jump the crank wire to the run wire, but I guess there is a microsecond break in power, and it won't start.  I thought I could run a relay, but it wasn't working either.  I'll have to see if I can figure this out. 

    My friends daughter is coming home from college (an electrical engineer major) and I'll see if she can come up with a simple way to wire it. 

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    PlumCrazyChris
    Mopar Muscle Cars of Austin
    Round Rock Tx
    70 Challenger 5.7, A518, A/C
    70 Challenger 340 convertible (Gone to Sweden)
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    Offline 1970GranCoupeConvert

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    Re: 5.7 Hemi install question
    « Reply #4 on: July 31, 2013 - 11:13:31 PM »
    MEH,

    Can you PLEASE provide some details and pictures of your installation?

    How does the 545 fit into the trans tunnel?

    Did you have to do any cutting of the tunnel or trimming of the transmission?

    How did you get the shift linkage to work?  (Slapstick or aftermarket)?

    Did you get the original speedo to work or some digital thing?

    Are you running a K frame or aftermarket?

    What radiator did you choose?

    What donor car did you get the engine and transmission from?

    Who do you recommend for the parts (you can reply off line if you like)?

    Are you running stock Chrysler accessories and brackets or aftermarket?

    THANKS VERY MUCH for whatever advice/help you can provide because like you I am about to take the plunge and I am trying to research as much as possible.

    THANKS AGAIN!!!
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    1970 Plymouth Barracuda Gran Coupe Convertible
    First Car (purchased in October 1985)
    Drove it throughout high school and early college (still do)
    Full Frame off (K frame off) Rotisserie Restoration completed in 1991
    Originally (and still is) a Rally Red, Black top with Charcoal/Silver Interior
    340 CID with Holley Pro-Jection 4Di
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    Rally Rims (color matched)

    Offline MEH

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    Re: 5.7 Hemi install question
    « Reply #5 on: September 03, 2013 - 09:50:34 AM »
    Hey everybody sorry for the late replies, been outa town working. My car is a 74 cuda, I installed a 2004 5.7 Hemi and 545rfe tranny from a 1500 truck. I bought a wirirng harness from autohotwire. Gas tank is from Roc Valley. TTI engine mounts and headers. radiator is stock as is the K member It looks like a 4 speed hump will work for the clearance needed for the new tranny. I still have to hook up the shifter cable to the tranny. I have started it but have not driven it yet.  Hope this helps.  I am hoping to work on it this weekend to reslove the computer power issue.
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    Offline Katfish

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    Re: 5.7 Hemi install question
    « Reply #6 on: September 03, 2013 - 10:59:05 AM »
    Watching, this swap is in my future plans.
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    Offline ShelbyDogg

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    Re: 5.7 Hemi install question
    « Reply #7 on: October 16, 2013 - 12:09:08 AM »

    Here are my photobucket pics of the circuits I drew and use for my fuel injected e-bodies.





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    Rob

    3 E-bodies, Megasquirt-1v3.0, Edelbrock Pro-Flo-1, Holley C950, FAST EZ-EFI; say no to carbs...yes to throttle bodies

    My Pace Car restoration thread:
    http://www.cuda-challenger.com/cc/index.php?topic=44869.0

    Offline johns cuda shop

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    Re: 5.7 Hemi install question
    « Reply #8 on: October 19, 2013 - 07:25:39 AM »
    Nice diagram . I guess the diode across the coil contacts on the relay protects the circuit ( EFI computer) from voltage spikes..
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    71 Cuda Gen III Aluminum 426 Hemi T56 6 speed 4.10 8.75 Modified & Lowered RMS coilover suspension Wilwood discs

    Offline ShelbyDogg

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    Re: 5.7 Hemi install question
    « Reply #9 on: October 19, 2013 - 09:54:04 AM »
    Quote from: johns cuda shop on October 19, 2013 - 07:25:39 AM
    I guess the diode across the coil contacts on the relay protects the circuit ( EFI computer) from voltage spikes..

    To the others that don't know about this spike;
    Put your fingers across a relay coil and hook it to a battery for a second then release it. You will feel a small shock. You don't want this little "spike" in your wiring.

    The collapsing field and generated spike is how your ignition coil works. I even wire diodes across my power window relays.
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    Rob

    3 E-bodies, Megasquirt-1v3.0, Edelbrock Pro-Flo-1, Holley C950, FAST EZ-EFI; say no to carbs...yes to throttle bodies

    My Pace Car restoration thread:
    http://www.cuda-challenger.com/cc/index.php?topic=44869.0

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