engine rotation

Discussion in 'Gas Engines' started by itselliott, Dec 26, 2015.

  1. itselliott
    Joined: Mar 2006
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    Location: Holland, MI.....home of S-2 Yachts

    itselliott Junior Member

    Reference: 1986 OEM Crusader 270 hp 350 cu in engines
    I am thinking of a distributor upgrade to Delco EST Dizzy:

    http://bpi.ebasicpower.com/shop/index.php?Screen=PROD&Product_Code=UMP9366-3M

    When researching I came across Michigan Motorz listing stating that there is a reverse rotation "specific" dizzy for this application.

    http://www.michiganmotorz.com/delco-voyager-marine-electronic-distributor-p-119.html

    I have 1-R H and 1-L H rotation motor ....but I find myself confused by the 2 different web pages. I already understand that one is a complete kit and the other is not. what confuses me is the "specif rotation" statement and the " one fits both" statement in the 2 listings. Can someone shed some light on this for me?
     
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Electronic distributors advance the timing through electronics instead of weights and springs, so rotation is not important. With mechanical advance, the base plate and weights have to be matched to the engine rotation.
     
  3. itselliott
    Joined: Mar 2006
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    Location: Holland, MI.....home of S-2 Yachts

    itselliott Junior Member

    I got that,...what about the actual rotation of the dist. drive gear? What I am reading is that the cam drives the dizzy in the same direction on both engines.....That said...WHY is there the $300 "up charge " on reverse rotation Dizzy from Michigan Motorz?..there has to be a reason.
     
  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    No idea. Can't see any reason for the extra charge.
     
  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    It all depends on how they do the reverse rotation. There's only two ways, the reverse cam grind (12756348 firing order) or the idler wheel cam gear arrangement, so the cam can turn the right way. It's often just a cross drilled main bearing setup and a gear drive arrangement.

    There a lot of "considerations" to think about, such as installing the pistons 180 degrees out, so the wrist pin offset is correct, plus a bunch of other stuff that make a counter rotation engine unique and durable.
     
  6. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    He says the distributor for the right hand rotation engine has a $300 extra charge.
     
  7. Barry
    Joined: Mar 2002
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    Barry Senior Member

    A couple of reasons. One that they do not make many reverse rotation distributors and the other which we found out the hard way, having had one of the reverse rotation distributors give out on us is that they have to machine a bearing into the bottom of the distributor to take care of the upwards axial load from the shaft and the bearing that rides on the cam gear which gives the shaft rotation.
    In a standard rotation the cam gear pulls the shaft down and the thrust is taken up by the bushing and in the reverse rotation, the shaft is pushed upward. This upward thrust needs to be dealt with.
    Hence the extra cost of machining in and supplying the upper bearing.
    The problem with these bearings which we found out is that over time, with a little moisture, they will rust, and fail

    This is the reason our mechanic gave us when I handed him about $450 for the new reverse rotation distributor
     
  8. powerabout
    Joined: Nov 2007
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    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    chev marine engines have gears driving the cam so it, distributor and oil pump go the same way.
    maybe they supply the firing order decal?
     
  9. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    As I mentioned, there are several considerations, even something as innocuous as the rear main seal is different on a reverse rotation engine (the seal has directional vanes). The part numbers for the crank are different, though some marine builders will just cross drill and make the standard rotation crank work, in a reverse setup. A reverse rotation distributor is called a ball bearing style, because of the thrust issue Barry mentioned, while the standard distributor bears the thrust on the housing bottom.

    To directly answer your question, yes the oil pump, distributor and cam run in the same direction, just the crank runs in reverse.
     

  10. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    I have a Palmer IH392 reverse rotation motor and normal direction motor in the boat.

    The difference, the cam is reverse grind and the distributer drive gear on the cam has teeth angled the other way.
    The distributer is identical except the driven gear teeth are angled the other way so as to match the cam drive gear. So even though the cam shaft turns the other way, it spins the distributor in the normal direction and since oil pump runs off distributer, it also spins the normal direction.
    Both engines use gears for timing, no chains.

    I always liked the way Palmer handled this, the only parts needed to change engine rotation are the cam, and the distributor driven gear and the starter.

    Any other reverse rotation motors done this way?
     
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