Checking my clearance numbers
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Checking my clearance numbers

  1. #1
    Senior Member Johnny2bad's Avatar
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    Default Checking my clearance numbers

    Hi,

    I have a good (fresh) 454 that has been sitting for many years.... wow, like just shy of 30. Time flies when you're having fun.

    It was in a hooligan street truck, PO had to go to prison for a bit and I bought it hearing it run and it was strong.

    Never used it so I just started to disassemble, clean and inspect the rotating mass.

    From what I've seen so far with the heads and pan off it's a basic 72-78 2 bolt main block. 3999289

    Stock bore, flat tops with valve relief cutouts. No specs but it has a lumpy cam from hearing it run years ago.

    Cylinder walls still have cross hatch. At this point I am assuming stock rods.

    Gonna be topped with a 2x4 tunnel ram in a v-drive drag boat and raced with an occasional river/lake cruise.

    Try to keep revs <6500 but you know how that goes. Just out to have fun, not rule the world.

    I usually run non oxy pump gas in stuff like this, may mix some AV gas if needed.

    Also have rev and timing control ignition for this project. Prolly use 10-40 earl.

    Would like to make sure the clearance specs are within marine tolerance. if not, make them so.

    After searching and reading way too many threads on BBC bearing clearance for boats .....here's what I got.

    Please correct me if I'm wrong.

    Piston wall to skirt_______.007

    Mains__________________.003

    Rods___________________.025

    Thanks for any input or comments. This is a great site.
    Johnny
    Posted from my Etch A Sketch

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  3. #2
    LP-25.com Infomaniac's Avatar
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    I would be OK with those numbers. I would look exactly where the piston manufacturer recommends measuring the piston. Add approx .0015 from their street car clearance if they do not recommend a clearance for marine use.
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    Senior Member Johnny2bad's Avatar
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    Thanks.

    Does that .0015 apply to both cast and forged pistons?
    Johnny
    Posted from my Etch A Sketch

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    Some guy obnoxious001's Avatar
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    Quote Originally Posted by Johnny2bad View Post
    Thanks.

    Does that .0015 apply to both cast and forged pistons?
    Best to actually call the piston maker. If they are stockers at .007" you are probably pretty loose. I personally don't go .0015" on a mild NA engine, usually just .001" over. Different piston designs and materials require different clearances. Some of the newer pistons with shorter skirts are suggesting less extra clearance on marine engines.

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    Senior Member Johnny2bad's Avatar
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    Quote Originally Posted by obnoxious001 View Post
    Best to actually call the piston maker. If they are stockers at .007" you are probably pretty loose. I personally don't go .0015" on a mild NA engine, usually just .001" over. Different piston designs and materials require different clearances. Some of the newer pistons with shorter skirts are suggesting less extra clearance on marine engines.
    Got it.

    Hope I can find out who and what the slugs are if I find some markings.

    Thanks
    Johnny
    Posted from my Etch A Sketch

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    Some guy obnoxious001's Avatar
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    Quote Originally Posted by Johnny2bad View Post
    Got it.

    Hope I can find out who and what the slugs are if I find some markings.

    Thanks
    Stock bore probably means stock, cast pistons. Are there two opposing valve reliefs?

    Did you measure the bore in several places to check taper and roundness?

  9. #7
    Senior Member Johnny2bad's Avatar
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    Quote Originally Posted by obnoxious001 View Post
    Stock bore probably means stock, cast pistons. Are there two opposing valve reliefs?
    Yup, reliefs at 1 and 7 o'clock. I kinda thought they might be stock.

    Looked up in'er the best I could standing on my head and they looked like cast.

    Quote Originally Posted by obnoxious001 View Post

    Did you measure the bore in several places to check taper and roundness?
    Haven't measured anything yet as it's on a low wheeled cart with the tranny still on and heads and pan off.

    Next up is to get it on an engine stand but it's -10 here on freakin MARCH 3 and I'm busy getting diesels started.

    Fek this winter.
    Johnny
    Posted from my Etch A Sketch

  10. #8
    Senior Member californiadreamin's Avatar
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    Quote Originally Posted by Johnny2bad View Post
    Hi,

    I have a good (fresh) 454 that has been sitting for many years.... wow, like just shy of 30. Time flies when you're having fun.

    It was in a hooligan street truck, PO had to go to prison for a bit and I bought it hearing it run and it was strong.

    Never used it so I just started to disassemble, clean and inspect the rotating mass.

    From what I've seen so far with the heads and pan off it's a basic 72-78 2 bolt main block. 3999289

    Stock bore, flat tops with valve relief cutouts. No specs but it has a lumpy cam from hearing it run years ago.

    Cylinder walls still have cross hatch. At this point I am assuming stock rods.

    Gonna be topped with a 2x4 tunnel ram in a v-drive drag boat and raced with an occasional river/lake cruise.

    Try to keep revs <6500 but you know how that goes. Just out to have fun, not rule the world.

    I usually run non oxy pump gas in stuff like this, may mix some AV gas if needed.

    Also have rev and timing control ignition for this project. Prolly use 10-40 earl.

    Would like to make sure the clearance specs are within marine tolerance. if not, make them so.

    After searching and reading way too many threads on BBC bearing clearance for boats .....here's what I got.

    Please correct me if I'm wrong.

    Piston wall to skirt_______.007

    Mains__________________.003

    Rods___________________.025

    Thanks for any input or comments. This is a great site.
    .025" seems just a hair loose
    Last edited by californiadreamin; 03-10-2014 at 10:06 PM.

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