Thread: Fast Fred's OMC Mod 50 secrets Thread #2

  1. #151
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    How do you connect up the second pump? Is it in series with the first?
    Where do you get your pulse from, existing spot teed off to both pumps or a seperate spot?
    Thanks

  2. #152
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    Default Interesting

    Maybe if I try two pumps I can pick up some more speed. Worth a shot anyways.

    Given there are a gazillion blocks out there to mess around with, I have tried a lot of different porting measures. Some worked, some not. I have not burned a lot of pistons, but I have burned a couple. Most of my burnt pistons result from failure in water pumps or to large a brass fitting that broke off. Smaller fitting with adequate diamenter is the way to go. The big blocky fittings will break sooner.

    Most of the serious racers know basic porting and tall or short and how it reacts on race courses of different sizes.

    I guess some new homework was just assigned to me this fall.

  3. #153
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    Does anyone know when they were making the first v6 how much work was done on working out which cylinders worked best for the 2 pumps?

  4. #154
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    Default RIB issue

    Fred

    Can you help me with a RIB issue?
    What do you do to fix the problem of a rib that I think someone has cleaned with a solvent that has made the plastersizer in the hypalon go sticky?

    Thanks
    Powerabout

  5. #155
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    Default Tandem or twin pumps?

    Most of my engines run the pumps in series. OMC actually produces a suction and pusher pump combination that is used on V-4's V-6's and the 30and 35 HP triples. Recently, I've run two conventional pusher pumps in parallel to a closed loop. Either way, make sure you're delivering a minimum 3.5 PSI at 5000+. It's best to put a guage at the cockpit and observe what's happening down the straight.

    Warning: With a single pump, installing bigger jets only serve to empty the carb bowls more quickly, burning a piston as you back off for the turn!

    The second pump is run from a hole drilled and tapped in the #2 intake runner about the same position as the #3. This is best done with the CCase off the engine. You will blow chips into the engine. As the casting wall is thin, Use high strength Loctite to seal/lock the fitting in place.

  6. #156
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    was number 2 just convient or was it calcuated for the series pump set up?

  7. #157
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    Default Equal length

    #2 was chosen for two reasons. 1) Shortest possible equal length pulse tubing can be used. Remember the tube increases CC volume. Keep them short as possible. 2) Use of a #1 pulse tube makes it almost impossible to install an electric starter. I prefer E-start.

  8. #158
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    Has anyone ever compared output of a VRO pump vs the older style diapham pump? Which has better pressure and volume, or are they about the same?

  9. #159
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    The Vro pump will pump way more fuel but as one of the posters here has tested them on his V4 and found they can't cope once the engine gets to about 7k I think he said.
    Understandable when you look at the size of the components

  10. #160
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    Question late style flywheels

    Hi Fred

    Do you know if the 92 70 new style flywheel is lighter and or can be modded?
    Is it diecast so we must leave it alone? They look sand cast ish?
    SST 60's didnt use I wonder why?

    Thanks
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