Torque Monster !

Big Block A body Tech

  1. mbaird

    mbaird mbaird FABO Gold Member

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    I know this subject has been raised before but it never gets really deep ....

    I have a 78 Dodge C-Class with a 440.
    What I have fantasized about is doing a stroker motor and an O.D trany for it.

    How would you build it ?

    What crank ? 4.15 or 4.25 ...
    What Rods ? How does rod ratio play into torque and reliability ?
    Bore ? I am thinking as little as possible to maintain wall thickness ..
    Heads ... Stock MH heads with extra cooling passages or Aluminum ?
    Pistons ? raised pistons domes to create quench using stock open chambers? Forged or Hypertechs ?
    Rings ?
    Coatings for heat dissipation ?
    Exhaust ... headers or factory truck center dumps ? 3” dual.
    Cam profile ?

    Lets have a deep analysis of this .

    DONT MENTION DIESELS. I KNOW THEY MAKE TORQUE .

    @Wyrmrider I read your posts on Speedtalk and liked your input on a similar subject but that thread died quickly.
     
  2. 273

    273 Well-Known Member

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    Torque in a NA engine is gonna greatly dependent on displacement. Most well built street strip level builds is gonna be 1.15:1 to 1.25:1 lbs ft per cubic inch. Which puts you between 575 to 675 depending on displacement.

    But what really matters is hp, a engine that makes peak torque of 625 lbs ft at 3000 rpm vs one at 6000 rpm, the one making it at 6000 rpm is gonna have about twice the hp.

    Besides budget 1st is I’d decide how much power You want to make, and with street level cam and cr will be around 1.8 hp per cfm of head flow with 10.5:1 cr and a 285 is cam. And start to narrow down parts selection from there.

    The larger the cid the lower the powerband will happen, needing less gear and stall. For a good street engine you’d probably want to keep displacement around 1:1 to 1:2 hp per cid if it’s more street strip or full race you can go higher. If you go under 1:1 it’s gonna be more like a truck engines powerband.

    so 500 cid would be good between 500 to 600 hp and 575 to 625 lbs ft. Which is gonna need a head that flows between 270 - 340 cfm to hit those numbers.
     
    Last edited: Jan 23, 2020
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    • AJ/FormS

      AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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      How heavy is that "C",
      what gears is it currently running?
      and what exactly are you trying to achieve?
       
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      • fishmens67

        fishmens67 Well-Known Member

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        :popcorn:
         
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        • mbaird

          mbaird mbaird FABO Gold Member

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          Its a 23 ft with an 11,300 gvw IIRC...
          gears are 4.10s in a Dana 70

          This discussion is not necessarily about what I need or can afford. But rather how the engine could be built to maximize the power potential for the application without sacrificing longevity.
           
        • 273

          273 Well-Known Member

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          There’s ton of stroker motors built over the last couple of decades, haven’t heard to many complaints of excessive wearing.

          For a street car I’d try to go with kits that keep the piston pin out of the rings, and if there’s a couple of rod length choices I’d go with the longest as long it was priced around the same as the other choices.

          If rod ratio and bore and stroke ratio bothers you I’d stick with 3.75 in both B and RB builds or otherwise not much can be done about it.
           
          Last edited: Jan 24, 2020
        • RustyRatRod

          RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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          For the street? The more reading I do, the more I like a short rod on the street. So if I were to build something like that, I would utilize the 6.358 rod. I also like the 4.15 crank as it's not as "out there" as the 4.250. Just one old man's opinion.
           
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          • rumblefish360

            rumblefish360 So close, yet so far away FABO Gold Member

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            Disagree with the head flow numbers for projected HP out put —- BUT —- always afford the best cylinder head you can for the given goal and engine size to meet the potential your looking for.

            This does not mean afford Predator heads for a 11 second ride.

            Also a cylinder head that flows said amount in
            theory, trying to meeting the goal, and doesn’t have the valve lift to take advantage of the heads capability is just wasting parts, time and money. Might as well get that ported Predator head to power the station wagon on a cross country trip without towing a trailer.
            (Don’t forget the 2bbl. BBD for mileage now!!!!)
             
          • rumblefish360

            rumblefish360 So close, yet so far away FABO Gold Member

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            Stock MH heads? Did you mean MW?
            Power goals?
            Basic usage? Regular motor home duties?
            Your question is very general. But I get the idea, I think.

            What would I do? Hummm

            If it were to be a hot rod?
            (LMAO- day dreaming ahead....)
            Hyper slugs not exceeding a 11-1 ratio
            TF heads, single plane, 850 cfm 2 inch headers (min.)
            4.15 crank, stock size after market rods (Scat)
            Coatings? Yes, where? Well, everywhere.
            Now back to the program at hand!

            Cam profile and specs depends on a hoard of info not supplied.

            The OD trans... Auto or manual, how many speeds and what is the final drive ratio? This changes the cams timing events and duration ...... a lot.

            In building a stroker for this motor home long distance travel duty, I wouldn’t really do more than a stockish like build. Just increase the compression, (Hyper slugs) use heat coatings on the piston crown, head chamber and the back side of the exhaust valves. 2 inch headers into a 3 inch dual exhaust. I don’t know what intake height you can get away with.

            I like this idea and topic.

             
          • 273

            273 Well-Known Member

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            I was basing it on an average street build with 10.5:1 cr and and a 285 ish cam with enough lift to work decently with what ever head was chosen. Probably .550 to .650.

            So what would be the correct head flow ?
             
          • roccodart440

            roccodart440 Well-Known Member

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            I'd be looking at a 440 source kit and pick one that accommodates a factory pickup.

            Honestly, you can easily make over 500ft/lbs with a 440 at 3500rpm or less and well over 400 ft/lbs at 2500rpm. This can be done with a SR style OOTB head and an over the counter mild cam.
             
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            • rumblefish360

              rumblefish360 So close, yet so far away FABO Gold Member

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              A loaded question without a clear answer to be given what ever paremeter your thinking of. The spread of 270 cfm to 340 cfm is extremely wide (70 cfm!) making it a super general blanket statement.
              Personally, for a motor home, I would not stroke the 440. But, this is an interesting topic and thoughts.
              The mention of stock heads is up there. I'm not sure if he was meaning Max Wedge heads.
               
            • mbaird

              mbaird mbaird FABO Gold Member

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              Again... this is a theoretical exercise. I am not really going to dump $15k into an old MH engine. We all have an idea of how to build a drag motor. Building a monster engine that has to pull a big load for long periods without overheating or wearing out in short order is a different science.
              Besides It would be cool to have a sleeper vintage Mopar MH !

              4.25 seems to be the max stroke with out oiling mods. What I am not sure about is the rod length effect/issues as related to dwell time , heat dissipation , piston pin height , piston skirt wear etc ....
              Heads for a torque monster don’t need to flow like a drag engine IMO... but a set of modern alloy heads has closed chambers for quench and dissipate heat better . Which means you could up the compression a bit to 9.5 range and still use mid grade fuel.
               
            • mbaird

              mbaird mbaird FABO Gold Member

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              If @Wyrmrider would chime in he could add a lot to the conversation. He has built a few engines for such an application and posted some tidbits about them on Speedtalk.com
               
            • rumblefish360

              rumblefish360 So close, yet so far away FABO Gold Member

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              It should be interesting.
               
            • 273

              273 Well-Known Member

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              I was meaning 270 to 340 cfm for 500 to 600 hp, so 270 would be about 500 hp and 340 would be about 600 hp, and in between cfm would be in between hp, with around 10.5:1 cr and a 285 ish cam. Wasn’t given the OP a blueprint to follow just what ruffly if you do this you get that.

              I missed that this was a motor home :) did see a video where someone put I think turbo LS engine in one.


              As for a motor home I guess I’d go with a 4.15 stroke and keep everything fairly stock. Possibly could add a very mild hydraulic roller. If we’re just throwing money at it.
               
            • rumblefish360

              rumblefish360 So close, yet so far away FABO Gold Member

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              Well, yeah, more head flow more power but I just wouldn’t do it at a massive port size. AndyF is doing/did a 470 build for his Duster that you should check out. It is really cool.

              For a motor home, IF I could fit a turbo need there, and I have zero idea what could be done, that would be a plausible route. A roof super charger would be better IMO if it could fit nicely. That’s torque on demand!
              Boom baby! Boom!

              The idea of a stroker with stock port heads equals a stock engine wasting cubic inches IMO. Hey m not saying there won’t be an improvement, but a wasteful one that doesn’t equal the increased size or effort.
              All of that he ranked in this Theoretical exercise!
              And that’s why I say, this is a very interesting topic.

               
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              • 273

                273 Well-Known Member

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                Yes you don’t need high flow heads for a motor home, I missed that part, Stock heads will flow enough to make the power you need.

                Stroking isn’t necessary about torque it’s about moving peak power closer to the operating range this case crusin rpm.


                If say your crusin at 1500 rpm the only way to increase hp at that rpm in a NA engine is to increase torque since the rpm is fixed and the main way to gain torque is displacement.

                The other way to do it would be to add more gear with stock stroke 440 to cruse at the same hp, either way is gonna add friction “wear” and burn more gas, lower rpm has the advantage of producing less noise.
                 
                Last edited: Jan 24, 2020
              • AJ/FormS

                AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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                hiway tractors (semis) have big engines and turbos. Heavy equipment also.
                Supercharging, of any kind would allow a lower cruise rpm, dual but Staged turbos could cover both ends.
                Just a thought.
                 
              • rumblefish360

                rumblefish360 So close, yet so far away FABO Gold Member

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                A bit complex for the average Joe?
                 
              • 273

                273 Well-Known Member

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              • mbaird

                mbaird mbaird FABO Gold Member

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                The thing about turbos and gas motors is heat. Pulling a long grade or driving a winding steep forest service road in the mountains could wreak havoc on the engine. Forgotto mention I live in the mountains .... Although some boost could help overcome the losses from 8000 ft + elevations !
                 
              • rumblefish360

                rumblefish360 So close, yet so far away FABO Gold Member

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                You could always keep the boost low. No need to twist it up real high. A few pounds does wonders. We just have to work on keeping it cool.
                 
              • 273

                273 Well-Known Member

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                The thing is what are you looking for more pulling power at crusin speed or fuel mileage ??

                It’s hard to gain both one gonna sacrifice the other.

                Say your crusin rpm is 2000 rpm and the 440 say is making 80 hp and consuming 255 cfm of air and fuel.

                To make 80 hp the 440 would have to make 210 lbs ft at 2000 rpm also. Now say you stroked it to 500 cid it would basically make 80 hp and 233 lbs ft at 1760 rpm and also consume 255 cfm of air and fuel. So you would spend a lot of money to drop 240 rpm and probably have similar power, gas mileage and wear and tear. You could spin either engine higher for more power at the cost of mpg or do the opposite.

                Adding a OD to the 440 would probably be the best bet unless the 440 is having a hard time pulling it now. Might have to add deeper gears depending on how low the rpm drops.

                As for torque power and mpg would be better off making the 440 more efficient and gain all 3.
                Which is hard and expensive and even with the miles you put on a motor home hard to recoup. But CR, thermal efficiency, lower intake and exhaust restrictions etc.. should be where to look.
                 
                Last edited: Jan 24, 2020
              • rumblefish360

                rumblefish360 So close, yet so far away FABO Gold Member

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                If you drive a supercharged engine like it wasn’t there, you’d get more mileage.
                 
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