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Heads

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    Smokin Whitie hondo jim's Avatar
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    Default Heads

    Head size to cubic in.
    I have a set of 325 dart heads how big of a cubic in.motor can I build.
    I have been told I can run up to 522 cubic in.

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    steelcomp was here
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    It depends on how many rpm you want to turn, and how much power you want to make. The heads should be flowed for actual numbers to work with.
    If God is your co-pilot, change seats!
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    Quote Originally Posted by steelcomp View Post
    It depends on how many rpm you want to turn, and how much power you want to make. The heads should be flowed for actual numbers to work with.
    Want to run from 75-8000 having the heads opened up to max .You can make more power with smaller ci with these heads you think

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    steelcomp was here
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    Quote Originally Posted by hondo jim View Post
    Want to run from 75-8000 having the heads opened up to max .You can make more power with smaller ci with these heads you think
    If you;re having them opened up to max, then they won't be 325's any more.
    You can make more power with bigger heads if that's what's needed. Sounds like you have the cart a little before the horse, starting with the heads, but that's OK. Get them done, measure the port volume, flow them and then you'll know where you stand.
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    Quote Originally Posted by steelcomp View Post
    If you;re having them opened up to max, then they won't be 325's any more.
    You can make more power with bigger heads if that's what's needed. Sounds like you have the cart a little before the horse, starting with the heads, but that's OK. Get them done, measure the port volume, flow them and then you'll know where you stand.
    Yea just put out a gang of money on these heads.Now going blown and doing a new short block.I hear the heads are ok for a 540 or larger.I know its about a combination.

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    Quote Originally Posted by hondo jim View Post
    Yea just put out a gang of money on these heads.Now going blown and doing a new short block.I hear the heads are ok for a 540 or larger.I know its about a combination.
    do you think 18 ci would make a diff.

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    What is the application? What are you looking to do?

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    Quote Originally Posted by Fiat48 View Post
    What is the application? What are you looking to do?
    Blown 540 with 325 heads 871 or 522 with325 heads 871

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    Hydro, flat, jet...what rpm...speed you want.....what are you looking for?

    The limiting factor of the internal combustion engine is the cylinder head. That said....you have a blower...so less head may get you by. Why I ask what boat you have, etc.

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    steelcomp was here
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    Quote Originally Posted by hondo jim View Post
    do you think 18 ci would make a diff.
    You're still not giving us enough info. Without some kind of reference to the head's size and flow, there's no way to tell. On that note, a blower covers a multitude of sins...what size blower are you running? Carbs or hat? Gas or fuel?
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    steelcomp was here
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    Quote Originally Posted by hondo jim View Post
    Blown 540 with 325 heads 871 or 522 with325 heads 871
    IMO it makes no difference from a standpoint of cubic inches. I think you'll have to turn the 871 considerabley to get much boost on either one.
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    Quote Originally Posted by Fiat48 View Post
    Hydro, flat, jet...what rpm...speed you want.....what are you looking for?

    The limiting factor of the internal combustion engine is the cylinder head. That said....you have a blower...so less head may get you by. Why I ask what boat you have, etc.
    Heavy 76 hondo runner,75 to 8000 rpm want to run 8.0 130 hows that for a round number.

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    I see no problem doing that depending on how good and free your boat is. I would do the 522 or less inches to better match the heads you have. Actually I would do 509. The blower will make up for it.

    The larger the motor is (air pump) the quicker it uses up the cylinder head. 7500 rpm with ablower in a flatbottom is a real realistic approach and so is 130 mph area IF the boat is a good boat..good bottom.

    Here's an example:
    Local here has a 541 with a 345 cc Canfield head...all good parts, etc. 6/71 blower, gas and carbs. At 4% OD he can run 9 seconds at Red Bluff. About 14% over to do it at Phoenix. But....117 is all the speed the boat does. I can e.t. the thing 8.80's....mph is just not there. Never will be because his boat is a ...well...POS.
    By the way...he runs a 25 gear 7800 rpm. 11 1/4 x 16 prop.
    Last edited by Fiat48; 01-20-2008 at 08:03 PM.

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    Quote Originally Posted by Fiat48 View Post
    I see no problem doing that depending on how good and free your boat is. I would do the 522 or less inches to better match the heads you have. Actually I would do 509. The blower will make up for it.

    The larger the motor is (air pump) the quicker it uses up the cylinder head. 7500 rpm with ablower in a flatbottom is a real realistic approach and so is 130 mph area IF the boat is a good boat..good bottom.

    Here's an example:
    Local here has a 541 with a 345 cc Canfield head...all good parts, etc. 6/71 blower, gas and carbs. At 4% OD he can run 9 seconds at Red Bluff. About 14% over to do it at Phoenix. But....117 is all the speed the boat does. I can e.t. the thing 8.80's....mph is just not there. Never will be because his boat is a ...well...POS.
    By the way...he runs a 25 gear 7800 rpm. 11 1/4 x 16 prop.
    Thank you for the info fellas

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