What heads, what impeller????
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What heads, what impeller????

  1. #1
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    Default What heads, what impeller????

    i have a 78 Charger 18ft boat, i finally sold both of my Olds motors. now im ready to gather and build a Chevy for it. i have a stock 12JG with a place and im assuming a "A" impeller. im not looking for a million horsepower, i would like to go 70-80 range in short blasts and pull tubes and play around, im planning to rebuild the jet as well.
    So if im looking through ads for a 454, should i get a large oval motor and port it slightly and run a "A" type impellor at lower rpms or should i get rectangle port heads and run more rpms with a smaller impeller? any cost effective ideas? im new to Chevy stuff and i have read up a little bit, but their isnt any substitute for experience...and its much cheaper to learn from you guys...

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    Senior Member H20MOFO's Avatar
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    Fwiw, I don't think you are going to see 70-80 with a set of ovals and a mild build,jmo.
    Last edited by H20MOFO; 09-01-2008 at 03:16 PM.
    Another Hot Boat refugee

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    I could always list it on ebay thats worth 20mph easy...probably do 70+ at half throttle... okay maybe not 70 or 80 but lets say 500hp or more

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Now decide on the RPM you want. If you want muscle to pull toys & Skiis, don't go smaller than a "B", an "A" is better. That means under 6-grand RPM wise with under 700HP on the "A".

    Under 6-grand, with a 454, go large oval and either have factory iron improved, or go aftermarket, and still have some bowl clean-up done.
    My porting work would have only cost about $1400 (including valves) to my iron, but, we found a few issues and settled them to both my and the porter's satisfaction as the best way.
    Cracked seat got 8 exhaust seats replaced
    Leaking guide (above the cracked seat) got all replaced and went downsize to 11/32"
    That forced new retainers, and keepers so went to 10* keepers.
    3 pressure tests instead of 1
    I honestly feel I gained more porting my heads than I would have gained from a box, for the same $$$$.
    I gained 400RPM against my Aggressor "B", no other changes.

    If you go over 500 inches, then consider smaller rectangles, unless you go way over 500CID.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
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    Sit N' Spin Jetaholic's Avatar
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    Quote Originally Posted by H20MOFO View Post
    Fwiw, I don't think you are going to see 70-80 with a set of ovals and a mild build,jmo.
    I beg to differ



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    BTC cardcarrying member sunkisst's Avatar
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    Default I Agree

    Quote Originally Posted by Jetaholic View Post
    I beg to differ
    Mine is 461,.030 over 454,flat top pistons,oval port,open chamber...850 DP Holley...81.1 MPH @4400 RPM...maybe mine is ''the right combo" ,Ill take it!!!Gullwing,12jg,loader,shoe,AA alum,stuffer,droop,ride plate...nothing special...

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    Sit N' Spin Jetaholic's Avatar
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    And mine's hitting 79mph at 5400 with an AB impeller. 461, .030 over 454, dome pistons, 9.5:1, Holley 750dp, RPM Air Gap intake, Aggressor droop w/2* down wedge, no shoe or rideplate.



    Quote Originally Posted by HammerDown
    Kendall L-427 Super Blu...extreme-pressure (ep) lithium complex keeps my thrusting balls happy
    Quote Originally Posted by back2k5 View Post
    Well I am putting in a nice stereo system in the Carrera...maybe Ill put on some rap and turn the scoop sideways

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    I'm not sure weather to shake my head or beat it into the wall. One guy says ovals can't get a 454 in a low pro jet to the 70-80 mark. The other says can't use rec ports under 6,000RPM......................COMMON GUYS!!!!!!!!!

    If you don't know any better don't answer the questions, just ask them

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    Quote Originally Posted by squirt View Post
    I'm not sure weather to shake my head or beat it into the wall. One guy says ovals can't get a 454 in a low pro jet to the 70-80 mark. The other says can't use rec ports under 6,000RPM......................COMMON GUYS!!!!!!!!!

    If you don't know any better don't answer the questions, just ask them
    no sh*t!!

    Quote Originally Posted by H20MOFO
    Fwiw, I don't think you are going to see 70-80 with a set of ovals and a mild build,jmo.
    I've got large ovals with a .510 lift cam running 75+ at 5100 rpms. No shoe, a homemade rideplate, dual plane intake and a vacuum secondary carb.

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    Thanks guys i appreciate what your saying, i kinda was guessing a 454 bored 30-60 over and a healthy cam with large ovals that have been ported and cleaned up, a nice 850ish dp carb and balance the rotating bits, stick with a "A" or so imp depending on rpms and cam choice, sounds like maybe im at least on the right track here. and ill rebuild the pump so its ready to rock...sound pretty good?

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Quote Originally Posted by 78 Charger View Post
    Thanks guys i appreciate what your saying, i kinda was guessing a 454 bored 30-60 over and a healthy cam with large ovals that have been ported and cleaned up, a nice 850ish dp carb and balance the rotating bits, stick with a "A" or so imp depending on rpms and cam choice, sounds like maybe im at least on the right track here. and ill rebuild the pump so its ready to rock...sound pretty good?
    That should give a good solid hard running combination as long as you don't go too long on the duration and send the power RPM out of where you want it.
    Solidify the combination with head flow info and go to one of the cam grinders like cstraub and he'll help you out on that call as well.

    Best of luck to you.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
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    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

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    jetboataholic HawaiianJet's Avatar
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    Quote Originally Posted by 78 Charger View Post
    Thanks guys i appreciate what your saying, i kinda was guessing a 454 bored 30-60 over and a healthy cam with large ovals that have been ported and cleaned up, a nice 850ish dp carb and balance the rotating bits, stick with a "A" or so imp depending on rpms and cam choice, sounds like maybe im at least on the right track here. and ill rebuild the pump so its ready to rock...sound pretty good?
    Build a 496!!!

    HJ

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

    Quote Originally Posted by mako shark mark View Post
    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.

  15. #13
    Senior Member H20MOFO's Avatar
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    I didn't mean to become the poster child for oval ports suck tonite either, for the record I said I doubt you will get to 70's with a mild build and ovals .Flame away.
    Another Hot Boat refugee

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    Senior Member ol guy's Avatar
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    Quote Originally Posted by 78 Charger View Post
    Thanks guys i appreciate what your saying, i kinda was guessing a 454 bored 30-60 over and a healthy cam with large ovals that have been ported and cleaned up, a nice 850ish dp carb and balance the rotating bits, stick with a "A" or so imp depending on rpms and cam choice, sounds like maybe im at least on the right track here. and ill rebuild the pump so its ready to rock...sound pretty good?
    Hey charger, A 78 18ft charger hull is a southwind 7 degree bottom splash and a 454 built right with a pair of 049 ovals the right cam and carb set-up can see 80 IF again IF you spend alittle money on the pump and bottom. An a impellar is all you need stage 2 blue print and a staight bottom, ride plate and shoe. If you feel so inclined I would move the intake back 3 inches while the intake is being cut for the shoe. Done this before and the combo works very well. IMLAO. M

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