Thread: Johnson "70mod"

  1. #171
    Team Member hupiveneilija's Avatar
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    Quote Originally Posted by filthy phill View Post






    are you saying that you get 7,000 rpm plus using small carbs ?
    Yes, with 1.21/1.37. Aint that funny!

    👌
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  2. #172
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    Want to see that caliper on the throat!

  3. #173
    Team Member LittleCharger's Avatar
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    Quote Originally Posted by hupiveneilija View Post
    Yes, with 1.21/1.37. Aint that funny!

    ��
    you must have a bad tach

  4. #174
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    Yes,im so glad it stops everytime 7100 so cant be afraid of revving it too much!😂😂

    Do have meter to 8k but have to calibrate it somehow. There is tiny hole behind it, just need to know exact rpm so can adjust it.

  5. #175
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    do you think I only have the small 60hp carbs ? ha ha now that is funny

    I have 3 sets of black top 56 cu in oval port carbs,
    2 sets are the small 60hp originals that came on both my 1995 60hp motors,( model BE60TLEOC )
    and 1 set I got after searching for a long time to get the 70hp black top carbs.

    I will take some new pics of both the 60 hp small carbs and 70hp big carbs over the next couple of weeks.
    I will not be taking the big ones off until ive had a few runs with the boat over the next couple of weeks.
    I started it up today, first time since about September and even running on stale fuel it idles fine and I let it run for about 40 minutes. even in 32 degree heat.

    https://www.youtube.com/watch?v=KiN8772sGXc

    https://www.youtube.com/watch?v=zdqbicMmv0c

  6. #176
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    Quote Originally Posted by filthy phill View Post
    do you think I only have the small 60hp carbs ?


    No I dont but would like to see how You measure them, so that i can measure mine right.

  7. #177
    Team Member hupiveneilija's Avatar
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    Request for the audience.
    On the left Stock 329835-1 head milled -3mm. That leaves 2,6mm material thicknes in the thermostat opening. I think someone somewhere wrote that 0.1in is aprox the limit where these heads start warping more easily.
    So this is what goes to the engine next. If its not enough then take more off of it.

    Had long conversation with the guy who did small chamber head. He was suprised that it streches so up on rpms, especially cause it was made for stock rev range. Although he made it so that it dont cut revving like a knife but let the motor spin up.
    For the next summer he will make a specific head for my use considering all other mods i make, durations and so on.

    So we will see how it goes.
    Attached Images Attached Images  

  8. #178
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    wow 3mm is a lot to have taken off, that is 118 thou !!!!!

    you might just about be lucky with this much taken off .
    I think normally people only take off a max of 80 thou, some racers have gone to extreme of 100 thou ?

    you need to put the chamfer back as it acts as a transition area between the squish-band and the combustion chamber itself.
    the angle of chamfer needs to be like the original.
    with this much off the head you should have extremely high compression.

    hope that works good for you and does not get distorted..

  9. #179
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    Rather than referring to the amount that is taken off, all should be referenced to the standard SST60 head which has a combustion chamber depth of 0.450 in and allowable limits of +or- 0.010. When I use to race the modified 56ci had two heads that measured 0.400 and 0.380. These had compression over 200 psi but trying to remember 20 years ago is a bit difficult. I think it was around 220 psi. While the .400 head was fine the .380 started to crack and warp.

    Stephen
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  10. #180
    Team Member LittleCharger's Avatar
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    I think based on what you have removed pocket depth is probably around 0.500, stocks heads vary so you could be on either side of this hence the reason Stephen refers to the pocket depth end result. I would suspect that Stephen's motor was decked to at least the sst60 specs as well.

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