Chevy Connecting Rod Stroker

Discussion in 'Fox 5.0 Mustang Tech' started by mercurycapri, May 31, 2013.


  1. mercurycapri

    mercurycapri Member

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    I'm in the process of rebuilding my 302. I'm going to stroke to a 331 but was wondering if I can use a chevy 5.7 rod instead of the 5.4 rod.
     
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  2. 88LX5.Oh

    88LX5.Oh Advanced Member

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    What I want to know is how this misconception got around that rod length makes different cubic inches.
    Only 2 things that dictate cubic inches are bore and stroke. You could put a longer rod in a stock 302 and guess what? The stroke is still 3 inches and the bore would still be 4 inches.
     
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  3. 65ShelbyClone

    65ShelbyClone Founding Member

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    All it takes is a little arithmetic.

    Deck height - half the stroke - rod length = compression height at zero deck.

    8.2" - (3.25" ÷ 2) - 5.7" = CH
    8.2 - 1.625 - 5.7 = 0.875" of space for the ring pack between the pin center and quench pad. In other words, not going to happen. 5.485" is the realistic maximum rod length for a 331 if using a 1.090" CH piston meant for a 347.

    Why do you want to use such a long rod? The 3.25" stroke and a 5.4" rod still nets a decent 1.66 rod:stroke ratio.

    No one said anything about rod length affecting displacement. :shrug: 331 stroker kits use a 3.25" stroke crank and 5.4" rods. He wants to know if he can use a 5.7" rod instead.
     
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  4. 88LX5.Oh

    88LX5.Oh Advanced Member

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    Yeah I probably should have thought into it more, because like you said, he didn't say he wanted to use the 5.7 rod to make it into a 331. But any time people in my area mention connecting rods they think it's some awesome trick to gain more cubic inches by going with a longer rod. My bad OP lol
     
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  5. 65ShelbyClone

    65ShelbyClone Founding Member

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    True, it is a common point of confusion among people just getting started with engines. I'll be the first to admit that the math and mechanics are not intuitive for most people and it gets even less intuitive the higher you get.

    Like how a "centrifugal" force pulling outward from the axis of rotation doesn't exist in proper physics. ;) Plotting piston motion relative to crankcase rotation actually requires calculus if you want to take the rod length into consideration.
     
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