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  1. #1
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    5.7 rebuild with twins - need advice

    Prelude: Bought a project 05 magnum from a guy last year and motor was in pieces between 1-4 years. Put it all together and put some hard miles on it before I spun a bearing. Need some advice before I go down a hole I can't climb back out of. This would be my first performance engine build.

    Goal: Have a car that's wickedly fun to daily drive but also not fearing that at any momentit's gonna spit rods or pistons. I have a friend who has a scat pack charger (mostly stock) that i'd love to see in my rearview mirror.

    Known issues so far: Block needs to be bored, Crank is f'ed up and lifters need to be replaced.

    An old neighbor is a well known engine builder in my area but he's more old school. Has multiple clients with 2000hp big blocks and I've seen funny cars at his place. He's willing to help me out but admitted that he has done tons of rebuilds on the police hemi's but has not done any high hp builds on them. I was wanting to go with twin turbos but his advice was sit on it and that he can get motors to naturally put out more hp's then guys with turbos. My fear is the price tag that will come with that. He knows the owner of scat crankshafts and is going to put together a list for me in the next few weeks. In the meantime, can I get some feedback from you guys?

    Rotating assembly: Does anybody have anything against scat forged parts?
    Displacement: Going boosted, is there any reason not to go with a 392 stroker?
    Heads: Will factory 5.7 heads with a port and polish be sufficient?
    Cam and lifters: Recommendations? From what I'm reading, mds delete is a must.
    Fuel Upgrades: Whats the limits on the factory fuel system? Are injectors the only thing needed?
    Tuner: Who can be recommended?
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  2. #2
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    What’s your goal?
    Old school guys do not like turbos cause they were not made for “power” back in the day. No way can he touch the hp that you’ll get with the turbos without being 5X the cost.
    I would stick to near stock displacement. Compression ratio will depend on fuel available.
    Honestly, short blocks from our venders are hard to touch on the price.


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  3. #3
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    392 strokers tend to outperform the stock 6.4ls by a slight amount.
    Being that it’s a pre-vvt motor, there are some nasty cams out there that make great power on strokers.

    It depends on your end goals but I would take a step back and realize that, yes, a 500-700rwhp monster of a motor would be great to have but everything around it is going to need to be replaced/built in order to make it a consistent daily.

    If it were me with limited funds, I would build a 392 stroker at a lower compression, get a radical custom cam and some solid heads. The lower compression will make a little less power now but you can throw turbos at it later if you want and yes a 392 at a reasonably low compression is entirely safe for turbos at a reasonable psi later.

    As I was doing the stroker, I would look into a rear end conversion (Getrag LSD) and possible driveshaft swap. Assuming your trans has no issues.

    Spread your money around the car and make it safer, longer, rather than throwing it all at the motor and breaking something else after.

    It always comes down to $$$ though.


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  4. #4
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    Quote Originally Posted by DBL.DWN View Post
    What’s your goal?
    Something that I can tinker on at nights, have fun without eating a hole in my savings. I also enjoy doing the work myself and learning as I go. I've done rebuilds but always with factory parts and gotten a lot of miles out of the motors but still have lots to learn.

    Quote Originally Posted by Newoldchallenger View Post
    If it were me with limited funds, I would build a 392 stroker at a lower compression, get a radical custom cam and some solid heads. The lower compression will make a little less power now but you can throw turbos at it later if you want and yes a 392 at a reasonably low compression is entirely safe for turbos at a reasonable psi later.
    Can you recommend a head and what compression would you aim for in this scenerio?

    Quote Originally Posted by Newoldchallenger View Post
    As I was doing the stroker, I would look into a rear end conversion (Getrag LSD) and possible driveshaft swap. Assuming your trans has no issues.
    I've been looking into the getrag. I had a diesel in my teenage years and fried drivetrain components is something I'm very familar with unfortunately.
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  5. #5
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    My go to head builders are High Horse Performance or Modern Muscle Xtreme. You can call either and they can direct your build to exactly what you want.
    Depends how many psi you are planning to push and how you want the car to feel under the curve and the quality of the tune. Anywhere between 8.5-10:1 is decent boost compression on a built motor.
    Lower compression=more sluggish under the curve but more boost can be thrown at it.
    Higher compression=faster under the curve but less boost capable.


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  6. #6
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    I understand tuning has a lot to do with keeping a motor together. I'm reading that 5-7psi is the most you want to go on a stock bottom end before asking for issues.

    Both hemi's I've rebuilt had shattered ringlands on stock motors. I'm assuming thats the weakest link? Has anybody ran just forged pistons? What would the max recommended psi be?
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  7. #7
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    You have to remove the rods to do the pistons....just put forged rods in when you do it, then you won't have to redo the rods later after one bends or breaks.

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  8. #8
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    ^x2

    Do it right once.


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  9. #9
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    Ran by the engine builders place and he’s telling me if I’m boosting it, get the forged crank.
    3AEA5A01-CDFF-4C72-A1FC-DBBF48351B0B.jpg
    Last edited by Unpopular; 09-12-2019 at 03:40 AM.
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  10. #10
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    You can buy a fully forged short block for what you're going to spend on crank, rods, pistons and labor to install them all.

    HEMI Engine Builders - 5.7L Short Block

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