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books for building a 4-71

Discussion in 'The Hokey Ass Message Board' started by RADustin, Nov 21, 2011.

  1. RADustin
    Joined: Aug 16, 2011
    Posts: 192

    RADustin
    Member
    from Louisiana

    this guy said this is a "stock front cover"

    [​IMG]

    so can I put the 6 bolt flange cover off the "back", or in the diesel world, the "front" and put it on the end with the gears, orientied so that the 6 bolt opening is on the drivers side?
     
  2. RADustin
    Joined: Aug 16, 2011
    Posts: 192

    RADustin
    Member
    from Louisiana

    the gears would be towards the front of the engine when I mount it up right?
     
  3. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,955

    gas pumper
    Member

    In theory, yes. But. The GM cover did not take any stress. When you hang the snout on there it's a lot of force from having all the drive forces pulling that snout down. That aluminum cover isn't real thick and beefy. I really don't know if it ever is a problem. Maybe it's nothing to worry about. --probably the old timers ran the GM cover with the drive snout bolted on.

    Your six hole cover only supported the governor assembly which maybe weighed 5 lbs and was "L" shaped and was also attached to the cylinder head. So the factory didn't figure on a lot of forces on these covers.

    Yup, gears to the front
     
  4. RADustin
    Joined: Aug 16, 2011
    Posts: 192

    RADustin
    Member
    from Louisiana

    so I guess I could take that 6 bolt cover and move it from the end it is on to the other end making the now "top" side the "bottom" side on the other end. This would keep the 6 bolt flange on the rotor that spins clockwise.

    then I can get a new "rear" plate that has the beefed up bearing flanges.
     
  5. RADustin
    Joined: Aug 16, 2011
    Posts: 192

    RADustin
    Member
    from Louisiana

    this is assuming the double rollers are under the end that accepts the hose and not the one with 6 bolt flange.
     
  6. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,955

    gas pumper
    Member

    Simple answer, Yes. :)
    As long as the oil drains don't hang out in space. I pretty sure it will work. see how it looks.

    Different housing in the back cause now you want a sealed up cover and lube the bearings with a grease fitting. At least that's what everybody else does. For street, the strenght of the GM would be OK, but than you still need to cover the bearings. So the new covers take care of that.
     
  7. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,955

    gas pumper
    Member

    Roller bearings are always on the end away from the gears. Ball bearings are double row on the gear drive end.

    Rollers on the end they are so the rotors and shafts can expand and not bind the bearings.
     
  8. RADustin
    Joined: Aug 16, 2011
    Posts: 192

    RADustin
    Member
    from Louisiana

    Once I get time to rip it apart I think everything will make much more sense.


    Thanks for helping me out! really appreciate it.
     
  9. RADustin
    Joined: Aug 16, 2011
    Posts: 192

    RADustin
    Member
    from Louisiana

    what about when I prune the flanges off? should I use steel bolts or fit some kind of aluminum stud in there?

    I was thinking when I drill and tap the bottom flange on the blower....to not drill all the way through and bottom tap the holes. Then use steel studs to mount it on the manifold. Sound right?
     
  10. you can run the stock "6 bolt" cover on the front of your street blower.

    I lent a stock cover to a bud this summer for his blown alky motor, cuz his BDS cover was leaking. It made it all season, 'til the last race. The motor was a little cold, sneezed a bit, and the stress popped the front cover. Ended his day.
     
  11. RidgeRunner
    Joined: Feb 9, 2007
    Posts: 892

    RidgeRunner
    Member
    from Western MA

    Do they still reverse them? (I was led to believe it was due to the blower going from 'scavenging hot exhaust' to pressurizing intake...
    Please expand on this?[/QUOTE]

    To the best of my knowledge GM has always used the term "scavenging" for whatever reason. In reality the blowers are on the intake side and keep the airbox/intake ports pressurized to keep the exhaust going in the right direction out by the exhaust valves/ports.

    Ed
     
  12. RidgeRunner
    Joined: Feb 9, 2007
    Posts: 892

    RidgeRunner
    Member
    from Western MA

    In theory: 4 71 cu in cylinders = 284 cu in. The GM/Detroit's are 2 stroke and require an intake charge every revolution to the 4 stroke Cad's every 2 so the blower should feed twice the displacement designed for, 284 x 2 = 568 cu in given the same drive ratio.

    One kicker is more volume capability or operating pressure doesn't always mean more actual flow through the entire system. Restrictions anywhere along the line [intake or exhaust port limits, headers, pipes, etc] can increase the pressure readings when the flow volume tops out....

    I agree that in some cases an easier spinning 671 can be a much better match than a hard spinning 471, could take less power to drive and build less intake charge heat. Compromises, compromises......

    Ed
     

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