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Thread: Stroker ideas

  1. #1
    Canadian Beaver Inspector jkindt's Avatar
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    Stroker ideas

    Anyone know if the webs from a domestic engine could be used to construct a longer stroke fuji crank? Would it take some machining to narrow the webs? What about snowmobile cranks? I have been thinking about a Stroker project using a SLT if I can find one.


  2. #2
    thester71's Avatar
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    Quote Originally Posted by jkindt View Post
    Anyone know if the webs from a domestic engine could be used to construct a longer stroke fuji crank? Would it take some machining to narrow the webs? What about snowmobile cranks? I have been thinking about a Stroker project using a SLT if I can find one.
    typically the stroke of a motor is changed with the rods, not the crank.

  3. #3
    Moderator beerdart's Avatar
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    Quote Originally Posted by thester71 View Post
    typically the stroke of a motor is changed with the rods, not the crank.

    Not true the crank stroke is what determines stroke no matter how long the rods are. Stroke=distance from crank center to rod pin center.

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    Canadian Beaver Inspector jkindt's Avatar
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    The distance between the center of the crank pin and the centerline of the crank is equal to 1/2 the total stroke. The rod length just changes the distance the piston is from the crankpin on its journey up and down. By using a longer stroke with shorter rods, the piston does not extend higher than it would before, but it does drop further into the cylinder.

    Does anyone know how close to the top of the cylinder the piston gets in a stock 780? I know the rods are 120mm from piston pin centerline to crank pin centerline, but I am not sure of some of the other measurements. I guess I may have to pull out the caliper and do some precise measurements. If I have room to toss the piston up an extra 1.5mm I may build a crank with 780 rods on a 785 core to get 68mm of stroke. Then I just got to calculate port height in relation to crank degrees to see how far the porting is changed. I may be able to compensate a little with a 1mm cylinder base gasket which would result in the piston only extending up and extra 0.5mm beyond the stock deck height. In fact...now that I am thinking about this, I may just try it with my 650 jugs and extra case I have sitting here just to see if I can get it to work before I commit to getting 780 jugs, pistons, and modded heads to build the Stroker! I love experimenting!!!

  5. #5
    thester71's Avatar
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    Quote Originally Posted by beerdart View Post
    Not true the crank stroke is what determines stroke no matter how long the rods are. Stroke=distance from crank center to rod pin center.
    My bad I thought rod length determened the stroke. you could not change the stroke by rod lenght?

  6. #6
    Moderator beerdart's Avatar
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    Quote Originally Posted by thester71 View Post
    My bad I thought rod length determened the stroke. you could not change the stroke by rod lenght?

    Piston travel will always be the same weather the rod is 3" or 6" the travel/Stroke will be the same.

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    thester71's Avatar
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    [quote=beerdart;1267628]Piston travel will always be the same weather the rod is 3" or 6" the travel/Stroke will be the same.[/quote

    thanks for the info, I'm still learning

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    bowsniper's Avatar
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    I believe thats why a 327 chevy back in the day was quick revving up the r's. Shorter stroke on the crank thus quicker rpm's.

  9. #9
    Canadian Beaver Inspector jkindt's Avatar
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    And also why guys took the crank out of a Chevy 400 and put it into the 350 to make a 383 Stroker! Less moving mass than the 400 and more displacement (and torque) than the 350. Plus the big valved heads matched up perfectly to the 383 displacement.

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    I'm sure you've seen this already, but these would be the guys that can guide you in the right direction.

    http://www.greenhulk.net/forums/show...light=1010+pro


    Maybe they even have a stroked crank webs laying around the shop already?

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