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Thread: My Kilo Motor

  1. #1
    Team Member 850cc racer's Avatar
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    Default My Kilo Motor

    Hey guys so im going to have a crack at the kilo record over here in aus for 1250cc mono. its currently set with a boat the same as mine but with a 920cc on it at 83mph i think it is.

    Im wanting to have a go at it but with a 814cc.

    I have a hustler 75hp, Phil's mod 50 pistons and the matching rods, im going to use my straight in 5pedal front with the 1inch carbs on it.

    what im needing to know is what should i do it it, it'll be fingerported, but im thinking it'll need to be spinning well into the 7's
    i also know this motor will only be good for a kilo run not normal circuit racing..

    my current motor does 75mph, its 814 fingerported with a single throat front, 2-1 gear ratio and 12x23 @6500rpm.

    i have 2.4-1, 2-1, and like a 1.85-1 gearboxes for it and many props. 12x23 12x25 13x23 13x27 and so on.

    all help is muchly appreciated!

    850

  2. #2
    Team Member 850cc racer's Avatar
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    Hey guys i had a pm from a member advising me that my boats only doing 60.7 by a formula from some website.. this is not a "slanging" reply or anything like that just wanted to let people know the speed is definitely true and not made up!! a website formula isnt real time situations.

    help with the internals of this kilo motor is muchly appreciated.

    thanks.

  3. #3
    2010 SRG 3 CYL CHAMPION 88workcar's Avatar
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    If it is going to be a one time deal, put some serious compression on it and put it on racing fuel. I think that 1" carbs are rather small for that engine, but I definitly am not an expert on that engine. Good luck keep us posted.

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    I would have thought the tallest ratio and engine as high as you can get it.
    ( get a tow onto the plane..it that legal?)

    Just a thought but..
    6500 sounds a bit low when a sst60 should be doing 7 to 7500 ( according to the manual ) with shorter rods more cubes and 3 x 1 1/2 carbs and an average exhaust and you can go to town on your exhaust.

    How much did you raise the porting to suit the long rods?
    Have a play here and you can see how much retarded the port openings become when the rod gets longer
    http://www.torqsoft.net/piston-position.html
    Or if you have the head off a stock rod engine with same porting, check the timing and compare it

    Anyone got a M31 port timing map?
    Where's Fred when you need him?

    Pitch x rpm
    -----------
    ratio x 1056

    = theoretical mph

    I think the rough part is always the prop pitch when most blades have progressive pitch and cup what do you actually use ? I think there is some trick with lipstick..you will need to ask Ron H

    Small stuff....use ATF in the gearbox
    make a sleeve up so you can remove reverse gear...
    Use race fuel not Av gas ..Longer rod is more prone to detonate than a shorter
    I have heard of people taking the wp impeller out if you run a LWP.....never tried that one.

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    Quote Originally Posted by 850cc racer View Post
    Hey guys i had a pm from a member advising me that my boats only doing 60.7 by a formula from some website.. this is not a "slanging" reply or anything like that just wanted to let people know the speed is definitely true and not made up!! a website formula isnt real time situations.

    help with the internals of this kilo motor is muchly appreciated.

    thanks.
    With the specs you gave, 1st post I find potential speed to be 70.79mph. Im not trying to cast doubt tho just to say there are variables on the boat beyond arithmetic while #s are cut & dry. The 1.85 :1 ratio with the 12 x 23 prop @ 6500Rs could potentially go 76.4. I dont know much about the powerhead except to say it will need to produce power at much more rpm. for that 83mph+ mark. At 2:1, 23P youll need a minimum of 7700 Rs to reach 83.8 & thats before subtracting slip/resistance that can vari from about 90% [very efficient] or less.
    What I do to get these #s is Pitch times RPM divided by 12, times 60 divided by 5280, times Ratio. [.5 in this case]= Potential Speed. To get ratio I divide the low # of gear teeth by the high #. for instance Yamato 14/15s = .933:1 using .933 to multiply. Best of Luck with that run for the record.

  6. #6
    2010 SRG 3 CYL CHAMPION 88workcar's Avatar
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    In the defence of 850, last evening I tested 2 22p props, at this time my engine will only turn up to 6900rpms. With one prop I ran 60.9mph and with the other I ran 69.9mph. And with my reg prop 26p cleaver at 6600 rpm I run 77mph.
    I think that either his pitch or gearing is not a good number. Or even the tach may be off. 850, is your current speed GPS? The picture sure looks like 75mph.
    And I agree go with the tall gear and prop to it.

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    Quote Originally Posted by 88workcar View Post
    In the defence of 850, last evening I tested 2 22p props, at this time my engine will only turn up to 6900rpms. With one prop I ran 60.9mph and with the other I ran 69.9mph. And with my reg prop 26p cleaver at 6600 rpm I run 77mph.
    I think that either his pitch or gearing is not a good number. Or even the tach may be off. 850, is your current speed GPS? The picture sure looks like 75mph.
    And I agree go with the tall gear and prop to it.
    Im guessing that too, Most guys are using gps nowadays so one of values is off. The boat couldnt possibly trim better if its hangin where the pic shows it. This will be about prop every bit as much as motor or ratio.

  8. #8
    Team Member 850cc racer's Avatar
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    Hey guys yeh it was with two different gps's that we have checked the speed of it.

    im going to have a look at the torqsoft website for sure thanks for that one.

    on the exhaust side of it.. cos ill run a tuner in the midsection ive been told i should dry that out so ill exit all water from the head?
    also i should port match the exhaust?

    does all this sound right? i understand i can block the water return in the sandwich plate..
    how do i port match though?

    thanks guys for all your replys

    850

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    Default The record is...

    Here's the record
    OUTBOARD MONO HULL CLASS SPEED RECORDS (Kilometres per Hour) AS AT 2 AUGUST 2009
    1250cc
    MONO HULL
    STEVE'S JEM
    S Medaris
    131.58 KPH
    Dargle NSW
    8.8.93


    http://www.ausapba.com.au/download_index.htm
    download rule book
    last few pages

    Will they let the 49er into the 800cc class as the UIM used to do?

  10. #10
    Team Member 850cc racer's Avatar
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    Hey Powerabout thats the one. seems i have to do 84mph which will be including the +2%

    i started to play with the exhaust ports this afternoon and copied them from the 814cc thats already done.
    im going to send it away tomorrow to have the fingerports put in it.
    i have the mod 50 map Fred sent me some time ago so they'll be copied from that

    anyone have any suggestions on what head, igntion, fuel, jets should be?

    as i mentioned im going to use the straight in front with the 1inch carbs

    thanks
    850

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