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  1. #1
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    intake manifold mods crossflow

    I was contemplating(as I was looking at a manifold)opening up that little groove that the primer system uses. Would that allow the respective cylinders to pull extra fuel from the other carb barrel? I was thinking about opening it up to 3/8" wide and maybe 1/4 to 3/8 deep. Am I wasting my time? Or will it actually do something beneficial?

    Or would I need to make it wider?

    what about bad side effects?

    Its just me studying something and going..........hmmmmmm.

  2. #2
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    the intakes on the v6 merc's are sometimes "cross drilled" to achieve a similar effect to what you're talking about. it helps mid range punch but negatively effects idle quality and makes tuning more difficult. maybe racer will be along shortly. he will know for sure what would happen in your application...
    Josh Peterson

  3. #3
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    I appreciate the input Nitro Rat

  4. Likes nitro_rat liked this post
  5. #4
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    it wouldnt be the first mod I would make to as xflow, imho its a top end improvement only.

  6. #5
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    Its not the first, at all. Its a list of little things. I will have the engine apart to clean up the intake tract, clean up the ports, work on the adapter's square edges and more. It looks pretty simple when I have a milling drill press at my disposal at work. I am trying to make it the most efficient air pump that I can without losing anything on the bottom. If I can boost midrange I want it. You get the idea. I am literally looking at every piece on the engine and evaluating if it is help or hindrance to my goal of being efficient.

  7. #6
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    Quote Originally Posted by keefallan View Post
    Its not the first, at all. Its a list of little things. I will have the engine apart to clean up the intake tract, clean up the ports, work on the adapter's square edges and more. It looks pretty simple when I have a milling drill press at my disposal at work. I am trying to make it the most efficient air pump that I can without losing anything on the bottom. If I can boost midrange I want it. You get the idea. I am literally looking at every piece on the engine and evaluating if it is help or hindrance to my goal of being efficient.
    what are you starting with 140, 1 5/16 or 1 3/8 carbs and a light boat so you are over 50mph?

  8. #7
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    Hull, I am still hunting for...........yes I would be over 50 mph in any boat I'd own and my 175 has 1-3/8 carbs. My previous small bore 235 pushed my tank of a work boat(kencraft) 53-54 during a test with a horrible prop etc. I hung it on a Ranger(heavy boat) I restored at the time and it pushed it to 70. That was a bone stock 235 that I built from parts I had and a brand new block I found from a parts dealer just sitting in a box. Basically this is the same engine as that one with bigger bores. But I am tweaking it a little..........like I posted.

    Sorry I failed to mention the engine size at first. I figured that all the omc guys have seen all my posts lately and know what size the motor is.

  9. #8
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    I am going to move this to my last thread so that there is only one build out thread for the motor.......... so post the comments on the "175 building" thread. I still want to know about this intake manifold clearancing............can someone please advise about that? I did look at the manifold more today and am tempted to open that notch all the way across at the present depth it is now. It reminds me of a dual plane manifold on a car......the relief cut all the way across instead of just that 1/8 cut for the choke.

    All right done posting in this one.

  10. #9
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    To b honest. I can think of 2 people that u need to talk to that "racer" or James Perry. Perry dont get on here much no mo but can PM u his # , the guy is a genius at these motas and making power all way thru power band

  11. #10
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    don't cut the manifold the tunning , after gets nuts ………….jmo

  12. #11
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    Can you elaborate?

  13. #12
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    I think he is saying the signal confuses the carb at low speed

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