How big C.I. BBC
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How big C.I. BBC

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    Senior Member carreradude's Avatar
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    Default How big C.I. BBC

    Some day when I win the lotto, or rob a bank, I would like to build a large cube BBC. My Q is how far till you trade size for longevity. It will be an N/A pump gas deal with a T/R on top. Is a 632 gonna have crazy rod angles? This will be a jet boat app. And some guesses on HP it will have? I know cam selection will have a lot to do with power output. Maybe target 5800 rpm on a AA? This will just be a lake or river cruiser with the occasional flooring of the loud peddle. Thanks for any input!!

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    If you keep the stroke to no more then 4.375" and do the rest with bore this will enhance the longevity of the engine due to the fact the piston speed and windage issues will not require exotic parts to build longevity. IMO anything over this stroke in a BBC needs to be a drysump in a boat, especially if she is going to be run quite a bit.
    Chris Straub
    Straub Technologies

    3HP is an A$$ Whooping!!! JW

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    New here Beer:30's Avatar
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    Keep an eye on BoostPower's new proprietary CNC block. 800 cubes.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    Distinguished Member David 519's Avatar
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    With standard bore spacing and a tall deck, 632 is about it. Lots of people say the long stroke/"bad" rod angle don't work but you sure see a lot of them in asphalt drag racing. I've never run over a 4.5" stroke, so I can't say from personal experience. Now a days, there are a lot of options on bore spacing, deck height and heads, the only real limit seems to be one's check book. Not hard to use up most of $100k on a new 5" BS based big inch motor. At the same time, when is it no longer a "BBC"!!
    I've done a few 4.5" stroke motors and they work well. However, based on my experience for my use (lower $$, conventional head lake/bracket boat), I'm a big fan of a 565 (4.25 stroke x4.6" bore, preferably tall deck). Seems the best all around compromise for mostly off the shelf parts to run pretty good. Again, $$ and application defintely drive a lot of ones decision...

    Oh snap, I misread the OP and made my reply too general. For a max RPM of 5800, I wouldn't hesitate to use a 4.5" stroke (598 with a 4.6" bore). Not to disagree with Chris but it's only another 1/16" per side more stroke and will generally be easier to build from off the shelf parts (cheaper). My current motor is a pump gas 580" deal in a flat. We spin it a bit higher (7200 or so) and use it similar to you. After a season of beating on it in a lake application, it still looks like new inside. Plumbed it for NOS this winter and plan on racing it a few time next season...
    Last edited by David 519; 01-29-2012 at 10:34 AM.
    Quote Originally Posted by gn7 View Post
    ....... David 519 is 100% correct........

    Quote Originally Posted by fuelinmyveins82 View Post
    .....I think people forget that racing is supposed to fun. Losing shouldn't be discouraging it should motivate you work on your pile to make it faster.....

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