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Thread: 302 Yamato to 500 CC MOD

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    Administrator Ron Hill's Avatar
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    Default 302 Yamato to 500 CC MOD

    I have 5 302's and are looking for a sixth. At the APBA Annual Meeting in Reno I saw several pictures of 500 CC MOD Hydros. I thought they looked more than cool. I was wondering what it takes to make a 302 Yamato into a 500CC MOD.

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    Add an exhaust pipe, mod the gearcase and water pick up in most any way you like, short centersection is always nice and fuel pump and tank removal makes it look like a race motor

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    Team Member DeanFHobart's Avatar
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    Quote Originally Posted by Ron Hill View Post
    I have 5 302's and are looking for a sixth. At the APBA Annual Meeting in Reno I saw several pictures of 500 CC MOD Hydros. I thought they looked more than cool. I was wondering what it takes to make a 302 Yamato into a 500CC MOD.
    Ron,

    I'm doing two myself. Cool.....................
    Dean Hobart
    Thanks GheenoeRacer thanked for this post

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    Tim Weber
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    Cliff Johnson out of Indiana has a very nice mod kit.

    He has all the pieces and parts and it works pretty darn well out of the box. I think you can buy the kit through APBA?

    His number is 317-258-2776.

    Tim

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    G&M Racing mercguy's Avatar
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    Quote Originally Posted by Ron Hill View Post
    I have 5 302's and are looking for a sixth. At the APBA Annual Meeting in Reno I saw several pictures of 500 CC MOD Hydros. I thought they looked more than cool. I was wondering what it takes to make a 302 Yamato into a 500CC MOD.
    ...

    here ya go Ron...

    http://www.shop.apba.org/Yamato-Modi...Kit-modkit.htm
    Daren Goehring
    63-R
    DSH, 500ccmh, 750ccmh


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    Quote Originally Posted by Tim Weber View Post
    Cliff Johnson out of Indiana has a very nice mod kit.

    He has all the pieces and parts and it works pretty darn well out of the box. I think you can buy the kit through APBA?

    His number is 317-258-2776.

    Tim
    I second this. Eric Vanover uses Cliff's kits, and he has proven it works. From what I have seen of it, it is a very simple install. It also does not take anything away from the stock engine if you wanted to run stock with it again, you can simply unbolt it.

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    Team Member mmgabe's Avatar
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    do you bore the cylinders to get your 500cc?

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    Default 500cc

    Quote Originally Posted by mmgabe View Post
    do you bore the cylinders to get your 500cc?
    No, it wouldn't be possible. The 302 is actually a 396-400cc engine. It can only be taken .050 over and that wouldn't get it nowhere near close. The reason it does 500cc category is just technicality. It can actually run with 30cid mark30H mod mercs. Those mark30H's are 500cc actually and the Yamato, though smaller and only two cylinders, will take them all day any day and outlast them.

    The best thing to do to start in mod with a Yamato is gear-case shape refinement. Just reduce the drag, jack it up and prop it right and it will run. All the other stuff is very good for balance in turning, but more optional than gear-case work is for speed. The gear-case is an area that is a "must" to get right if you go mod. As for exhaust, the expansion chambers are real nice to have but they are for quietness while utilizing a custom shortened mid section as a rule. Open megaphones aren't allowed in APBA with Yamato's but according to some who race outside U.S.A with open pipes, the megaphone system is still just as fast. Quincy proved long ago that the "two into one" megaphones were better than separate mega pipes as well. If you have a stock 302, the "Two into one" megaphone is there in the tower housing as is. Good blueprinting of the Yamato powerhead, gear-case reshaping, and propeller set-up is the most important part for running MOD and you can win with just that, if the boat and handling thereof is good. To go back to stock, just invest in an extra un-modified gearcase and switch it out. Its cheaper and a lot easier. Takes about five minutes to do.

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    Team Member JohnsonM50's Avatar
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    I just drove a new 500 mh for the 1st time at LH pa. It is potentially a great ride but there's bugs to work out of mine. It's got a 102 w/ a slide pipe & is pretty fast. Now I just have to ramp up my driver game & work with the boat.

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    Default mod 500

    Quote Originally Posted by JohnsonM50 View Post
    I just drove a new 500 mh for the 1st time at LH pa. It is potentially a great ride but there's bugs to work out of mine. It's got a 102 w/ a slide pipe & is pretty fast. Now I just have to ramp up my driver game & work with the boat.
    What kind of speed and RPM did it do? If it is a single (2 into one) chamber, what is the length from the start of the lead pipe to where the deflector cone and stinger pipe connect as well as stinger length? Im curious about how those are able to work in sync with the action of the piston speed to port timing and tuned chamber length, because the chamber theories were always based on "one chamber for one cylinder" but not two working alternately. Two at the same time though (like the 350 pro opposed piston engines) would work two into one as they are working at equal action. I would like to do some calculations with info on the yamato mod single pipes so I can learn more and maybe figure them out. Thanks!

    About megaphones, they do work with alternate firing cylinders "two into one", but that's a whole different thing if I'm correct....

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