Pros and cons on stroke and bore combos?
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Pros and cons on stroke and bore combos?

  1. #1
    Senior Member Boat 405's Avatar
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    Default Pros and cons on stroke and bore combos?

    This is a bit of general question but I thought I would ask when looking at different combinations. Which are more favorable than others.

    Some of the combos I was thinking were as follows.

    9.8 deck
    4.6 bore
    4.25 stroke (565) or 4.375 stroke (582)

    Just thought I would start a new thread about different combinations that seems to work better than others, maybe it is more of a preference? I know that when buying cranks it doesn't cost much to go a little bigger stroke. But where is the trade off considering different combos have different frequencies and harmonics at operating rpm between 6000 and 7000.

    Hopefully I can get some answers good or bad to peoples experiences.

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    Resident Ford Nut Sleeper CP's Avatar
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    If your starting from scratch go with the 10.32 deck block and anything from a 4.25,4.375 or 4.5" stroke will work just fine

    The choice of BB Fords head's has never been better, so a 900-1,000 hp N/A engine is no problem

    Sleeper CP
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    Senior Member AzMandella's Avatar
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    I've been the big inch(stroke wise)that is. Not masive but a 514. Next time I'm going to go with a 429 stroke with a 4.5 bore. Not sure of the total inches but I'm going to go big inches,short strok and shoot for 8,000 RPM's

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    Talking about Chevy's. No offense.

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    Cantard 71hallett's Avatar
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    One thing that comes into play is your desired rpm. At what rpm are you seeking your power? A 4.385 stroke is not goint to like 8000 rpm on a 9.8 deck. 6000 rpm goal and your gona pull stumps.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Hey Widow, you stuck on the 9.8 deck height?

    My opinion for a jet running 6-7k is A 598 (4.6X4.5) with a 6.535 rod.

    Not a "big" price differance these days. A little more $ for the 4.5 crank/pistons and the heads to properly feed it but not huge.

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    Quote Originally Posted by Warp Speed View Post
    Hey Widow, you stuck on the 9.8 deck height?

    My opinion for a jet running 6-7k is A 598 (4.6X4.5) with a 6.535 rod.

    Not a "big" price differance these days. A little more $ for the 4.5 crank/pistons and the heads to properly feed it but not huge.
    No, not stuck on a 9.8 deck just thinking of ways to keep weight down. taller deck = more weight. Plus I don't know what kind of differences i'll be getting into with a tall deck. Honestly I don't know much about a tall deck.

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    Weight should always be a concern, just not sure how much you are giving up between the two. It would be nice to know the weight differance betwen a standard and a tall deck, then it would be easier to make the desicion. Can we remove the weight somewere else (or just deal with it for the added cubes/power) or is it too much to consider?
    If it was me, with that brand new GS hull you have, I would run it the way it is for another year and $ave up for my all alluminum 10.4+ deck spread port 632!!!

    Anybody know the weight dif between an iron std/tall deck??

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    Quote Originally Posted by widowmaker View Post
    Talking about Chevy's. No offense.

    Non taken,

    I know, I didn't have anything better to do at 10:45 last night

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    Really Big Member SilverEagle's Avatar
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    I don't know about GM castings, but a Merlin III weighs about 270 lbs. The difference between a 9.8" deck and a 10.2" deck is only about 5 - 10 lbs. One of the big differences, at least with the World Products blocks is the crank clearance: 4.375" for a 9.8 and 4.750 for a 10.2.

    The real weight savings comes with aluminum parts - especially the block. For salt water applications, you give some of your weight savings back because of the weight of the required fresh water cooling system.
    What, me worry?Ó¿Ò

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    Quote Originally Posted by Sleeper CP View Post
    Non taken,

    I know, I didn't have anything better to do at 10:45 last night

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    Default 9.8 - 10.2 or bigger?

    Widowmaker, i have been pondering this exact question, I know that alot of people go with the short deck for the savings of 5-10 lbs but - another question is?
    short deck - 565 10lb weight savings (approx) 4.6x4.25
    tall deck - 565 with as long a rod in as possible.....
    or spend twice the cash and go aluminum, (approx 100lbs savings).

    How much power does a hundred pounds of overall boat weight cost?
    -- for instance, does the 100 extra lbs take 100 more hp to break even? or is it more or less?


    Darin

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    steelcomp was here
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    There will be a HP loss with an aluminum block, so take that into consideration as well, weight loss over HP loss...which gains more?
    I'm a long rod fan...but the short deck 565 seems very popular. More displacement = more power potential, but there are tradeoffs when getting into seriously long strokes/short rods. Where the tradeoff is, is the big question. Endurance/high rpm needs different condiderstions than low rpm/short duration (drag/river/weekend warrior) applications. A lot of it also boils down to personal preference/experience.
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    Cantard 71hallett's Avatar
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    Quote Originally Posted by -XTC- View Post
    Widowmaker, i have been pondering this exact question, I know that alot of people go with the short deck for the savings of 5-10 lbs but - another question is?
    short deck - 565 10lb weight savings (approx) 4.6x4.25
    tall deck - 565 with as long a rod in as possible.....
    or spend twice the cash and go aluminum, (approx 100lbs savings).

    How much power does a hundred pounds of overall boat weight cost?
    -- for instance, does the 100 extra lbs take 100 more hp to break even? or is it more or less?


    Darin
    Around 30hp
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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