Porting question, or 2
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Porting question, or 2

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    Senior Member H20MOFO's Avatar
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    Default Porting question, or 2

    O.k so I have a set of heads that will support up to 509 cid. I'm building a 557 bbc. My Q? is to port or not to port?? My local guy says his expert can gain about 15%.(porting my heads) Edit I just read my own post and it sounded stupid even to me. I dunno what am I leaving on the table? I'm at altitude does that make it better or worse???(if I don't port)
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    There are a ton of variables that are involved in your question. BUT it really depends on what the heads did before they were ported.

    As a very generic comparsion, stock BB heads will most likely show a much larger increase % than AFR CNC heads will. so just saying that 15% is possible without knowing your current heads is beyond a guess.

    What makes you think that your heads will only support a 509?

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    Senior Member H20MOFO's Avatar
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    5325 You gonna help?? 557 bbc brodix bb 2 plus heads cc'd at 116, cam to be determined by chris straub. 9 to 1 comp. tt bassett headers I'm sure you deal with those all the time.
    Last edited by H20MOFO; 09-02-2008 at 08:53 PM. Reason: forgot bb,
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    steelcomp was here
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    Quote Originally Posted by H20MOFO View Post
    5325 You gonna help?? 557 bbc brodix bb 2 plus heads cc'd at 116, cam to be determined by chris straub. 9 to 1 comp. tt bassett headers I'm sure you deal with those all the time.
    What happened to your 496 with the ported ovals?
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    Senior Member H20MOFO's Avatar
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    I change my mind alot. It ended up being 557, now ny carb is too small,heads ,ect,ect,
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    Quote Originally Posted by H20MOFO View Post
    5325 You gonna help?? 557 bbc brodix bb 2 plus heads cc'd at 116, cam to be determined by chris straub. 9 to 1 comp. tt bassett headers I'm sure you deal with those all the time.
    Those are decent flowing heads that would probably handle 700 HP with no issues. I know Brodix says 509 max, but I think they would handle your motor. 15% is gonna be an outside max number with these heads, with Del West valves which seem to flow very well, and just about every porting trick out there. Lots of care has to be taken to work the seat area, plus guide area, and go easy on the short side radius. No sharp anything there. Combustion Chamber should be worked to help unshroud the valves. When its all said and done you should be able to get high 700-low 800's on gas. You said you are at altitude, so I'm guessing on the max power, as we build mostly at sea level. We have used these heads on an alcohol motor and seen above 900 Horse with all the porting that I said being done.

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    steelcomp was here
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    Good advice?15% would put you at over 390cfm. They aren't going to be 312cc's any more, either, are they. Why buy a set of heads for 2100.00 and put another thou (minimum for the amount of porting it would take to get 15%) when you can buy something already more than adequate for much less? You can get a 320cc CNC ported Canfield for 2500.00 assembled that'll do everything you need it to do. A set of Dart 325's as cast with roller set up goes for about 2450.00. The BB2plus IMO is too small for what you want to do. You'd have to spend $$ to get it to work or run one whopper of a cam.
    JMO
    Last edited by scott foxwell; 09-02-2008 at 10:08 PM.
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    What you want to be very careful of is "how" the air flows. I have seen heads with huge ports that have no velocity, and on the flow bench make less flow than ones with smaller ports that have been done correctly. We use a lot of Canfields with really good numbers. AFR's are excellent, but bring a big checkbook.

    Its like everything else on a boat. How fast do you want to go, how much do you want to spend.

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    jetboataholic HawaiianJet's Avatar
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    Quote Originally Posted by H20MOFO View Post
    I change my mind alot. It ended up being 557, now ny carb is too small,heads ,ect,ect,
    Uh oh, you've been watching 468bahner for too long!!!

    HJ

    ***FOR SALE*** 1978 19' Full Stringer Hawaiian Molokai Jet Boat w/ Berkeley 12JC-AB and Chevy 440 Tall Deck ***FOR SALE***

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    Oh yeah, Forgot to mention that the hull is a special mixture of speedcote, herculiner and rain-x, all blended together- good for another 8 mph top end.

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    Senior Member H20MOFO's Avatar
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    Your funny HJ, thanks Steel, yeh I'm a dumb azz I kept on telling my self 496, cause that's about all my chit is good for . So what did I buy a 557. Too late now.
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    cfm
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    CID's and rpm are big determinent on head size used. You mentioned cid's - what rpm are you planning on turning ?

    1) Call Brodix and see if they can, and how much $$$, to have your heads CNC ported as they offer new BB-2 Plus heads with this done. See http://www.brodix.com/heads/bb2.html

    2) Call known good head porters (not just 'some guy') and go over all the details (parts already in them too) with them. They'll tell you what would be better - x amount of porting or different heads, the $$$ of course, and etc,etc. Don't just say here you go. Have a good conversation with them laying everything out on the table. Ask, if they don't mention it, if a different head would be better.

    b) Don't jump the gun and say okay to whom you talk to first. Get other oponions. Unless of course, you already have a go to guy you fully trust and have a concrete relationship with.

    Then decide between 1 and 2 or nothing.

    Hope I typed my thoughts okay. SOmetimes hard to get thoughts thru the keyboard. Doh !

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    cfm
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    BTW: since new build, why 9:1 compression ? Is only 89 octane available near you ? Just going to 10:1 will make huge difference in how it runs.

    You mentioned 'at altitude.' How high ? If real high more compression will be your friend.

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    we have the bb2 plus sts cnc ported on a 505 bbc and when we got them wow they sure were perttyi think the cnc -2 would handle your 557 just fine.i mean your probably not gonna turn 7 grand with a 9-1 motor.good luck and i hope it works good for you.

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    Senior Member H20MOFO's Avatar
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    Thanks Guys. ummm as far as why 9 to 1 that's what I bought(used rotating assy). plus I hope to add a procharger or turbo or??? If my cylinders won't hone out,(has some surface rust) then I'll prolly go higher with the new slugs. From what I understand brodix will not cnc a used set og heads. Before I bought this I called my local motor guy, and I think his exact word were for $300-500 he could increase there flow 10-15%. I'd be happy in the 700-800 range(for now). Maybe throw a little spray at it down the road. Btw it going in a jet spinning an ab impeller. as far as r's I dunno 6k ish??? Maybe I should get a aa impeller and build more of a lower r deal.
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