Short Deck, Long Stroke Hemi

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by pulltab, Dec 8, 2017.

  1. pulltab

    pulltab Member

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    Old tractor puller here. For years we ran blown BBC's with a 4.5 bore x 4.5 stroke in a 10.2" block with good durability & power at 7500 to 8500 rpm .
    With quite a few 10.2" deck height Brad & TFX blocks out there for sale, what is everyone's though about running a 4.446 bore x 4.5 (or 4.375) stroke, Brad 5 heads, 14-71 HH, running a 7500 to 9000 rpm band, for durability & power. Looking for good torque more than high rpm HP.
     
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  2. youngtuner

    youngtuner Member

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    Problem I can see with that big of a stroke is you end up with a really short rod, that means there is a ton of side load on the piston at the bottom dewel area when the crank is switching directions.. If you could make it work I think it would be very hard on skirts and rings.
    I know there was a slight issue with the 4.150 stroke and the 4.471 bore with -.500 short combo. I know it has been worked out. but food for thought it there was an issue there could only be worse at 4.500
     
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  3. nitrowannabe

    nitrowannabe Member

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    You might have a problem with the fatheads small chamber. With a 14-71 you can hydraulic the engine because of the amount of fuel you need under a heavy load.Then the dirt gets loose and you have way to much fuel. A current combination with the hemi is 4.5 stroke, 4.310 bore and fuel heads. Mini rods and 2wd drive truck are successful with this combination . Call or text and I can put you in touch with another puller in North Carolina...301-758-8408.
     
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  4. Kamikaze85

    Kamikaze85 Member

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    A couple of buddies of mine run the latest Veney heads with a 4.44 bore and a 4.5 stroke - That thing is a BEAST.
    But as said, the Fat Heads might not like the big stroke - I hope to find out one day though, but would probably stay at 4.375 stroke to take the top off the side load and use the tallest deck block I could get my hands on.
    I know some of the top mini guys around here are running 4.25 stroke in a Fat Head engine with great success.
     
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  5. youngtuner

    youngtuner Member

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    We did a motor for a mini rod guy with a 14-71 with 4.467 bore and a 4.150 stroke short deck and BAE5 thing works killer. I know a lot of the big stroke veney stuff with the newer head (trying to be closer to a fathead than a hemi) tend to use .100 tall blocks and then add another .500 spacer on top of the deck before sleeves so they can get the correct rod ratio.
     
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  6. pulltab

    pulltab Member

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    When I built BBC's with a 4.5 stroke, I always used a 6.6 " or longer rod and never had an issue with skirt side loading, and yes the wrist pin was well up in the oil ring but was never a problem with pin buttons.
     
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