Engine Questions? Need help for a newbie
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Engine Questions? Need help for a newbie

  1. #1

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    Default Engine Questions? Need help for a newbie

    I have a fresh BBC 454 that is going in a 21 tahiti I already have the motor and I am pciking up the boat tommorow and I am wondering what is the best cam and intake manifold to run.

    the motor is 10.-1 comp
    I plan on running OT Headers and running them dry
    I don't want them to limit my cam selection I want a nice lope in the cam.

    and I am new to jets and wasn't sure where I should be looking to make the most power? do I want a cam and intake for lowend or should I be looking for something that makes power from 2200-6500 I was told by a friend that jetboats have to have certian cams but I doubt his word because he has never owned one... and as far as how the boat is going to use I am in florida and just plan on running up and down the river. no drag racing but I love speed so I want to make sure my topend is good.


    I was looking at running a air gap style intake manifold and cam is undecided. I also plan on roller rockers.

    thanks in advance for your help

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  3. #2
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    Depends upon the impeller size you are running in the pump. Any way you look at it you want something making power from 2500rpm and up.

  4. #3
    Resident Ford Nut Sleeper CP's Avatar
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    Do you plan on running a soild flat tappet, hydr. roller or something else ? Your RPM air gap will work great to 5,000-5,300 a single plane will out-perform it from 5,200-6,500 plus. How high do you want to rev it?

    Sleeper CP
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  6. #4
    Senior Member HKROB's Avatar
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    What heads are u running.

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    I just picked up the boat today and I am happy, it turns out the boat is not a 21' it is a 1973 18' tahiti which I wanted a smaller lighter boat but there isn't many choices in florida.


    As far as heads go I am 99% sure they are the rectangle port heads, motor numbers show it is a truck block but I belive it was originaly in a jet boat when it started life.

    the whole motor was rebuilt it has
    4 bolt mains
    rectangle port heads
    new rods but stock
    10.1-1 compression
    and as far as cam I belive I am going to go flat tappet cam
    I am looking to go with some roller rockers
    I am looking at the holley single plain intake manifold or the brodix they both look very similar.

    and what should this motor spin without issues. 5500-6000?
    and should I do arp rod bolts and main studs?

    Sorry for the dumb questions but I am new to jets and big blocks. I spend all my time working on my toyota 22r 84 pickup


    and now that I found out the boat is a 18' I want to see what this thing will do for top speed so I will do what it takes to get there hoping for mid 70's

  8. #6
    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    well Haulin, from the guy who has every wrong part imaginable (according to some), but still runs a dead reliable 8:1 500HP @5400RPM 454:

    rectangle port heads
    I prefer Large Ovals unless you plan to spin OVER 6,000RPM. The bigger port hurts flow velocity at moderate RPM.
    Had my Large Ovals ported,
    new rods but stock
    Plenty but I wanted ARP bolts (3/8" wave locs). The 3/8" knurled GM's are the VERY weak link.
    10.1-1 compression
    good, could even be 1/2 pt higher with care IMO.
    and as far as cam I belive I am going to go flat tappet cam
    Running a hydraulic flat of all the horrid things. Custom grind, and runs HARD.
    I am looking to go with some roller rockers
    I run Comp Cams Hy-Tech Stainless rolelr rockers, because of a personal dislike of aluminum rockers, period. Love my HT's. Picked up a used set, had them overhauled by Comp, new for 2/3 the price.
    I am looking at the holley single plain intake manifold or the brodix they both look very similar.
    I'm running your Performer RPM Air Gap dual plane, to 5400RPM without nitrous (500HP). 5,900 on the big gas jets.
    Again, IMO, if you keep those heads, a big single plane manifold will not help the 4-5,000RPM port velocity cylinder filling.

    and what should this motor spin without issues. 5500-6000?
    6,000 certainly. I get mighty close to it with a factory original 1978 CAST crankshaft.
    and should I do arp rod bolts and main studs?
    IMO, again, Yes. I did.

    The rest is all your decisions
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  9. #7
    northern member Canuc's Avatar
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    Quote Originally Posted by HaulinTail View Post
    I have a fresh BBC 454 that is going in a 21 tahiti I already have the motor and I am pciking up the boat tommorow and I am wondering what is the best cam and intake manifold to run.

    the motor is 10.-1 comp
    I plan on running OT Headers and running them dry
    I don't want them to limit my cam selection I want a nice lope in the cam.

    and I am new to jets and wasn't sure where I should be looking to make the most power? do I want a cam and intake for lowend or should I be looking for something that makes power from 2200-6500 I was told by a friend that jetboats have to have certian cams but I doubt his word because he has never owned one... and as far as how the boat is going to use I am in florida and just plan on running up and down the river. no drag racing but I love speed so I want to make sure my topend is good.


    I was looking at running a air gap style intake manifold and cam is undecided. I also plan on roller rockers.

    thanks in advance for your help
    with what your asking for and dry pipes i'd run a single pattern cam like a comp 294s . and be sure to run a single plane intake with a 800-850dp carb. with a b-c impeller you should pull around 6000 + ??? , dual planes are for milder prop boats that need the pull right off idle or jet's that are running a big impeller and not wanting to rev much over 5000 your jet with a b-c won't start puting any load on your motor till after 4000 . my .02 hope that helps

  10. #8

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    with the impellers is there a break down with the rpm range and impeller trim?

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    and would it be better to run dry pipes or should I look into water injected...

  12. #10
    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Quote Originally Posted by HaulinTail View Post
    and would it be better to run dry pipes or should I look into water injected...
    From the people who have tested the difference on their boats, no difference, so it's your call on heat and noise.

    I run thru-transom jacketeds.
    "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."
    H.L. Mencken

    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

  13. #11

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    I was looking at running TT but I would need to cut the holes and I can pick up a good used set of OT headers alot cheaper and seems like they would flow alot better then log TT manifolds.

  14. #12
    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Quote Originally Posted by HaulinTail View Post
    I was looking at running TT but I would need to cut the holes and I can pick up a good used set of OT headers alot cheaper and seems like they would flow alot better then log TT manifolds.
    They will, than LOG MANIFOLDS.

    I run TT headers, not so much improvement against these. TT JACKETED headers to go under an engine cover are damn pricey tho.

    I gained 50HP putting my headers on replacing my logs/snails. No other changes.
    "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."
    H.L. Mencken

    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

  15. #13

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    50 HP is a big difference I am going to try to find some OT headers for cheap but if I spend over $500 I am just goint to save up and buy some new TT rewarder's

  16. #14
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    If you want to run a hydraulic flat tappet call sherry @ clay smith and order part#H-300-8BHL the specs are .244 @ .050 straight across .570 lift straight across ground on a 108 lobe center works very well and is easy on parts

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