BBC Rectangular Ports VS Oval Ports
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BBC Rectangular Ports VS Oval Ports

  1. #1
    Gone in a Flash! Speed of Heat's Avatar
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    Default BBC Rectangular Ports VS Oval Ports

    I'm starting to collect parts for a N/A BBC 496 build for my 21'"daycruiser. This is a family ski/cruise deal, so reliability is important. I'm planning on all forged parts in the short block, ARP hardware etc. C/R around 10-1. Pump gas only. Max rpm 6000 rpm. Probably cruise at 4000 rpm. I'm shooting for lots of torque +600lbs and hp in the high 500s. I was originally thinking of going with AFR 310/315 rectangular port heads with the cnc chamber option. I plan on a roller cam around [email protected] duration cam with lift that will have a stable profile. (hopefully hyd), Air-Gap dual plane and 850/950 carb. I'm now wondering if it might be better to use a set of larger oval ports rather than the rec. ports to preserve the mid range. I don't want this to be a PIG at the mid range just to get bigger numbers at the top end. Any thoughts on this? Any one else have a combo that has worked out real good?
    Remember that the Ark was built by amateurs and the Titanic was built by professionals.

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    Jet or V Drive?

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    Resident Ford Nut Sleeper CP's Avatar
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    FYI: This might give you some info it's a 502 not 496 but close enough;

    http://www.performanceboats.com//showthread.php?t=451

    I'm not sure of the outcome of the rec heads you mentioned with an rpm air gap manifold and an 4150 carb. The Air Gap's are great pieces, but I think they start to reach their limit above 460" and anything close to 500" really like to breath (IE: Dominator carb)

    Just my .02

    Are you running header's?

    Sleeper CP
    Last edited by Sleeper CP; 05-04-2008 at 09:49 AM.

    "Dark Sarcasm"
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    Senior Member hotbo's Avatar
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    well if its a jet you really have no need for midrangethey cant tell what that is.

    on a 496 i wouldnt put oval port heads and a air gap intake.
    this info is for a jet if you a outdrive just scratch some of it.

    the afr heads are nice.good idea.might shop around and get a better price on them or some brodix out of the box heads are great pieces also.

    tall single plain,dart or brodix imo.atleast a 850 really like sleeper said dominator would be the best but you can get a 4150 style that flows 1000 cfm.

    cam sounds really small ,remember the more c.i.you have it will make a cam act smaller.hope this helps and good luck on the build,travis

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    Sorry, I forgot that important small piece of info--YES, its a V-DRIVE I am also planning to use Keith Eickart Thunder and Lightning cast headers-These are the set-up that RACEY and Brummett use on their builds.
    Last edited by Speed of Heat; 05-04-2008 at 04:07 PM. Reason: spelling and addition
    Remember that the Ark was built by amateurs and the Titanic was built by professionals.

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    Bump- anyone else want to add their 2 cents, all opinions welcome!
    Remember that the Ark was built by amateurs and the Titanic was built by professionals.

  9. #7
    cfm
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    Holley 850/950
    Vic Jr or Dart Rect
    AFR 305's (cnc chamber a plus)
    Correct Hyd roller
    9:1-10:1
    496-502cid

    Will make 600ft/lbs and change
    600-620hp by 5700rpm

    Example:
    Friend/associate of mine just got his 502 off of dyno with full accessories and full wet exhaust - yup, using the same KE exhaust, AFR's.
    517ft/lbs at 2500rpm
    560ft/lbs at 3000rpm
    613ft/lbs at 4700rpm
    592hp at 5600 rpm

    Remember, full wet exhaust, mufflers even ! Power steering pump, alternator, water pump ! Pump gas. As real world as it gets.

    Less than 10:1.

    If you want more details give me a PM.

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    Quote Originally Posted by Speed of Heat View Post
    I'm starting to collect parts for a N/A BBC 496 build for my 21'"daycruiser. This is a family ski/cruise deal, so reliability is important. I'm planning on all forged parts in the short block, ARP hardware etc. C/R around 10-1. Pump gas only. Max rpm 6000 rpm. Probably cruise at 4000 rpm. I'm shooting for lots of torque +600lbs and hp in the high 500s. I was originally thinking of going with AFR 310/315 rectangular port heads with the cnc chamber option. I plan on a roller cam around [email protected] duration cam with lift that will have a stable profile. (hopefully hyd), Air-Gap dual plane and 850/950 carb. I'm now wondering if it might be better to use a set of larger oval ports rather than the rec. ports to preserve the mid range. I don't want this to be a PIG at the mid range just to get bigger numbers at the top end. Any thoughts on this? Any one else have a combo that has worked out real good?
    With a .250" more of arm you won't need to worry about midrange, you'll be in good shape powerwise. For what you wanting the rectangles will work just fine. I would do a bowl blend on them. I would suggest a Victor Jr intake over the air gap. Your not going to loose any low end power with the CID you have. I would go roller to get more power under the curve.
    Chris Straub
    Straub Technologies

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

  11. #9
    Senior Member Xtreme 1's Avatar
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    In my opinion. For what thats worth... considering I just did a 489 last season, keep your compression as low as possible to make your desired or needed power. Remember you can't always get 91 + on the lake, water contaminated fuel etc. It gives you a little room in timing this little monster. Detenation has killed more engines due to lack of experience,no brains,alcohol, or the boat next to you that your trying to whoop and dont listen to what your engine is telling you. Dont get too crazy on the head size, meaning runner volume you most likely not going to spin this thing high enough to need them and definetly call 1-423-854-0007 and let Chris Straub set up your cam specs by the way go solid roller for that little extra there not that bad...

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