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Building NA 7.3 bottom for factory turbo truck

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Beerthirty, Jan 30, 2019.

  1. Beerthirty

    Beerthirty Registered User

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    Haven't built one before.
    Would like advice on engine kits, whether I need a PS rod for 6-8 psi factory style turbo and things near/related to.
    Just want put something decent/stout together for my father who tows a 5th wheel, rock, dirt etc up the mountain at 4ft elev.

    Mahl pistons vs others?
    Head gasket?
    If I use PS rods, which balancer and flywheel should I buy and send out with the rotating assembly for balance?
    Heads, some better than others?
    Porting ,I have a flow bench
    ...but should I bother?
    Something about 1/8 vs 1/4 oil feed to the turbo or injecter..?

    I'm new to these...so while I've read some things, I'd really appreciate some help from more experienced 7.3 builders. Thank you in advance.
     
  2. Randy Bush

    Randy Bush Full Access Member

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    What do you have for a core engine now?
     
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  3. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Since it appears that you're going to be using a N/A block and bottom end, I'll go with that. You won't have any issues with a completely stock bottom end with a goal of 6-8 PSI. You wouldn't even have to install head studs, but they are a good idea right now if there's even a small chance that you'll up the boost in the future. Think of them as insurance. The bottom ends of these engines are well built and can handle a lot of abuse. I am a believer in head porting. Thewespaul says that he sees lower egt's after porting heads. The biggest thing is to install a pyrometer with the probe in the "proper" location. The best location is within about 8" from the heads. There is a place on the driver's side exhaust manifold that most people use. This is for the most accurate EGT readings. With that low of boost, an intercooler would still be nice, but certainly isn't required. As for the oil port, don't worry about it being 1/8" NPT. The aftermarket turbos all are fed from this size of oil port. If you're going to use the same oil port as the Factory Turbo does, you can just get an adapter to go from 1/8" NPT to 1/4" NPT to use the factory fitting.
     
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  4. austin92

    austin92 Full Access Member

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    I wouldn’t worry about rods at that psi. Stock na will hold twice what you plan to run.


    Sent from my iPhone using Tapatalk
     
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  5. Oledirtypearl86

    Oledirtypearl86 Full Access Member

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    @Beerthirty a na block an hold that boost and like idibronco said the bottom ends of these motors are built for example I have a 86 6.9 with a hypermax turbo and I run 14psi pulling. 9k pound camptrailer in the mountains all summer long and the truck is reliable I hope you keep us all posted on the build
     
  6. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    To break it all down:

    Stock 6.9 head bolts- 7-10 max

    Stock 7.3 head bolts- 12 psi reliable, 15-20 max.

    Stock na bottom end- had failures at ~350hp but been pushed to mid 400s

    Stock factory turbo bottom end- haven’t found the limit of yet.
     
  7. austin92

    austin92 Full Access Member

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    If you do, please take pictures lol


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  8. Beerthirty

    Beerthirty Registered User

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    I picked up a crank, rods and block from a 89 truck. I have a turbo motor in the truck '93, makes what sounds like a rod knock on one cylinder...I wondered if anything else could cause that, bed Injector? Not a diesel mechanic.
    I figured I would buy a full kit, pistons, cam lifters etc and go grab some heads off another engine along with the covers. I figured I'd then take all the turbo crap off put it on the new motor then add a larger pipe and all that.
     
  9. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Before you invest all the money into a rebuild, make sure it’s a rod knock and not a fuel knock.
    With the engine running you can loosen one injector line at a time and see if the knock goes away.

    I sell rebuild kits and upgraded downpipes along with a lot of other goodies for these engines btw ;Sweet
     
  10. Randy Bush

    Randy Bush Full Access Member

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    If I had a turbo engine I would rebuild that unless it is trashed before a NA one. IMO a much better lasting engine.
     
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  11. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Exactly. I've seen literally hundreds of these engines and it's very rare for one of them to have a rod knocking or a spun bearing for that matter. I won't say that it can't/doesn't happen, but the few times that it does, it's usually from lack of maintenance (being run low on oil).
     
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  12. Kevo1288

    Kevo1288 Full Access Member

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    This is an awesome thread because I’ve been searching and searching for a 7.3 to regasket/rebuild so that I don’t need much downtime on my truck .... as long as you don’t plan on going crazy and just doing the simple bolt ons and ip advance etc an n/a would be fine.
     
  13. Beerthirty

    Beerthirty Registered User

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    How about a turbo replacement cam?

    Should I just use the stock na cam?

    Are they different to begin with?
     
  14. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Thewespaul told me that he always runs stock cams. Now, for my personal experience, I know that the butt dyno isn't very accurate, but I installed a Typ4 cam into a 6.9 that I stupidly put extremely high mileage heads on. I ported the heads, and it was N/A. That thing really ran good for a few miles before it dropped a valve. I guess that it kind of depends on what you're trying to do. I do have to admit that if the idiot machinist that I took my heads to wouldn't have shaved WAY too much off of the heads, then I would have installed that cam in the 7.3 that's in my truck right now. This just occurred to me. If you're talking about using a cam from a Factory Turbo engine, I'm not sure that there's much (if any at all) difference between the two. Typ4 mat have an idea. I hope somebody could answer this. I'm curious to know the answer.
     
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  15. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Specs never changes for any of the cams for the 6.9 7.3 or 7.3t from all the material I’ve read. Someone said awhile back there was a high altitude cam but I don’t buy it, if there was ever a change in cam specs there would be literature on it, just look at how much literature there is on the idit variant.

    You don’t need a cam to run that engine with a turbo, in fact you really don’t need to do a thing to that engine to run that amount of boost reliably. If you were running double that then you might start looking at head studs, but that’s about it.
     
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