Looking For More Rpm's
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Looking For More Rpm's

  1. #1
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    Default Looking For More Rpm's

    Ok here is what I have. 76 21' Omega Open Bow Day Cruiser. I have a jacuzzi wj with B impeller ( equivalent to berkley A from what I understand) It have a Ford 460 .030 over KB 22cc dish cast pistons, Ported D3 heads stock rockers and lifters ( Installing ported D0VE friday with 1.73 comp roller rockers along with a hydraulic place diverter) crane 288 Hydraulic flatty Cam 9( 226 230 duration .522 .530 lift 112 LSA), Dooley 10qt w/ windage, melling m84 std volume, truck rods, holley 850 mech. on top of a stealth intake, msd pro billet mech. set at 10 initial 38 full all in by 3000, summit ignition box, early style timing chain, and hardin logs without the neck down.

    I have seen 4600 rpm and 54-55 mph with this combination. I put a 1" spacer open and even tried 4 hole on this weekend and actually lost 300 rpm (4300 rpm & 47MPH on GPS). Im figuring with the head swap I will gain at least 400-500 rpm( I hope) haha. Aside from the obvious cast pistons is there anywhere you see that I may want to change such as the cam. I know the cam now calls for 9.5:1 which I am well short of. I am really trying my hardest to see 70 and need the rpms to get it done. By the way the pump has a loader and is fresh as well. here is a pic of the boat.

    Click image for larger version. 

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    Last edited by mygarageguys; 07-11-2012 at 01:53 AM.

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  3. #2
    Senior Member GT Jets's Avatar
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    Don't take this the wrong way.....

    Your expectations of 400-500 more RPM are totally unrealistic. IMHO with the cast pistons and low compression ratio I would leave well enough alone..

    Limitations include; the logs are killing the top end, the cast pistons are really not suited for anything over about 4,600 RPM (although there are probably some people on here that have 10,000 RPM 900 HP single carbureted small block Chevy's with cast pistons and never had a problem ), You have not stated where the camshaft is degreed in, oh and BTW, the 400-500 RPM will not buy you 15 MPH, not by a long ways...


    My constructive recommendations, start saving your tooth fairy money now to build a better short block in which to build upon, this should keep you from blowing stuff up.

    Next, put the boat on a diet, lose anything that is not necessary as far as weight, move as much stuff aft as you can, try to keep the COG at or about the harmonic balancer.

    Then the next logical thing to do is to ensure the hull is working as efficiently as possible and inspect the bottom of the hull for the parasitic "hook", not that you will be flipping the hull to remove it, but it would be better to know that it is there now, rather than later.

    It's funny, but sometimes just the tune, things like making sure the throttle opens the butterflies all the way, the plug gap is correct, the cam timing is proper, and jetting is appropriate, there can sometimes be a few MPH just hiding there waiting to be found..

    Most important have fun while being safe...
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

  4. #3
    Senior Member Futs's Avatar
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    Why so much timing? Back that thing down to about 32*

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  6. #4
    Senior Member jetboatperformance's Avatar
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    What do you belive the motor makes for HP and where ? also what altitude ?

  7. #5
    Senior Member 2002CP19's Avatar
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    Quote Originally Posted by mygarageguys View Post
    Ok here is what I have. 76 21' Omega Open Bow Day Cruiser. I have a jacuzzi wj with B impeller ( equivalent to berkley A from what I understand) It have a Ford 460 .030 over KB 22cc dish cast pistons, Ported D3 heads stock rockers and lifters ( Installing ported D0VE friday with 1.73 comp roller rockers along with a hydraulic place diverter) crane 288 Hydraulic flatty Cam 9( 226 230 duration .522 .530 lift 112 LSA), Dooley 10qt w/ windage, melling m84 std volume, truck rods, holley 850 mech. on top of a stealth intake, msd pro billet mech. set at 10 initial 38 full all in by 3000, summit ignition box, early style timing chain, and hardin logs without the neck down.

    I have seen 4600 rpm and 54-55 mph with this combination. I put a 1" spacer open and even tried 4 hole on this weekend and actually lost 300 rpm (4300 rpm & 47MPH on GPS). Im figuring with the head swap I will gain at least 400-500 rpm( I hope) haha. Aside from the obvious cast pistons is there anywhere you see that I may want to change such as the cam. I know the cam now calls for 9.5:1 which I am well short of. I am really trying my hardest to see 70 and need the rpms to get it done. By the way the pump has a loader and is fresh as well. here is a pic of the boat.

    Click image for larger version. 

Name:	IMAG0013.jpg 
Views:	57 
Size:	98.4 KB 
ID:	168609
    You shouldn't have lost with the spacer. How do the plugs look? Is it rich? I think the dove head is good for some compression. Is the cam in there strait up?
    Quote Originally Posted by schick View Post
    Hold it firmly on the ground, a few pelvic thrusts should do the trick. If not repeat till satisfied!

  8. #6
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    I have the cam installed straight up. As for GT Jets answer of saving up and building a stronger block, the current engine is full arp everything. I have a set of trw 2404 but need one more to have complete set. Valve decided to let loose on me and gave the piston a ride of a lifetime. Considering I'm doing the dove swap should I switch cams to say an xm278

  9. #7
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    By the way, I think with this motor I might b seeing 370 with the d3 on

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