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Thread: My Kilo Motor

  1. #211
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    Quote Originally Posted by pdt View Post
    Yes the triple I have is restricted as far as doing anything with the exhaust housing for sure.
    its not like the older type that could come off and be given a different exhaust manifold.

    the 120 psi really does surprise me, if mine was 120 I would dump it....I have 148..149 ..148.
    somewhere on here iwas told I need to get to atleast 165 psi and that maybe getting rid of the small reliefs could give me 10psi to help me raise it up a touch.

    im finding it all very confusing , but great reading

    The only way you can get to 150 PSI+ is with low porting and a factory head milled .120" or so. A custom head with tiny pockets is needed to make up for high porting. The reason is compression is not generated until the exhaust port closes. So, the higher the porting, the lower the top end compression reading.

    To confuse matters further, physics and architecture conflict in every engine. Consider that less swept volume (tall porting) combined with tiny combustion chambers means less air/fuel mixture available for combustion. Less air/fuel mix limits available power production.

    Get it now?

  2. #212
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    what we need is a 3 cyl with bolt on exhaust and its made from the 45 stuff so longer rods and more stroke

  3. #213
    pdt
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    The only way you can get to 150 PSI+ is with low porting and a factory head milled .120" or so
    do you mean can only get 150+ psi on a worked on engine, or do mean 150 + is not possible on an engine like mine, the later 56ci oval ?

    and 100 avgas over here is mental price if you can even get it without a civil aviation licence to get to the pumps at air field.

  4. #214
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    Default Compression vs octane

    Quote Originally Posted by pdt View Post
    The only way you can get to 150 PSI+ is with low porting and a factory head milled .120" or so
    do you mean can only get 150+ psi on a worked on engine, or do mean 150 + is not possible on an engine like mine, the later 56ci oval ?

    and 100 avgas over here is mental price if you can even get it without a civil aviation licence to get to the pumps at air field.

    Port shape with or without bridges doesn't matter; upper timing edge and combustion chamber volume determine effective compression ratio. Regardless of ratio, you need to tune for the best available octane. E85 or other alcohol modified fuels are good for octane and cooling. The downside is it must be flushed from carbs every time you're done.

    PS 100LL here is about $6 US/Gallon.

    Tim

  5. #215
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    The engine you ask for is readily available at BRP dealers........ The Etec 90.

  6. #216
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    Default compression question

    Quote Originally Posted by Fast Fred View Post
    you can mill the exhaust on the 56er and fix it. set it up like a Mod50, it's been done.

    150psi or 28cc head chamber is about the limit of pump gas.

    time to go fix some boats
    I'm not trying to change the conversation, but I am wondering what any opinion would be on what I have. My yamato 80 is 145psi exactly on both cylinders. Compression gauges can be a bit different though by a pound or so as Rick Montoya told me. But as far as pump gas goes, My 6NHR Champion Hotrod is reading 161psi on the top and 165psi on the bottom. It is an old 20cid racer. is this something I need to look at, as far as running pump gas? It is all completely stock with a carter carb. It doesn't look like it was used for alchohol at all. Any comment about this would be appreciated so I don't damage a piston or two. THANKS!

  7. #217
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    if it was handed to me to fire it up, i'd check the mix,see what the factory wanted,and use LL100at the factory mix to fire it in the test tank, once i had her bumpin, i'd check temp then the timin setup, see if it swings or stiff arm, after a check for excessive timin , all being good to there i'd make a Pull, see if she is lazy in the curve, if felt that she was i'd cut the LL100 to 50% and 50% regular gas then, make Pull. i may only cut in 25% reg gas, i'd have to see and feel it to know for sure.... gots to run...

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  8. #218
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    Hey Fast, funny thing happen to me last year, I threw some 87 oc. by accident in my 75 Stinger with 150 lbs. comp. She actually ran faster.

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