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Technical Motor Angle

Discussion in 'Traditional Hot Rods' started by Flathead Dave, Apr 22, 2016.

  1. Flathead Dave
    Joined: Mar 21, 2014
    Posts: 2,852

    Flathead Dave
    ALLIANCE MEMBER
    from So. Cal.

    I have my motor angle set up for zero degrees at the carb and zeroed side to side. My frame is also zeroed out. Is this good on the bubble or should I go down another 1/2 degree on at the rear of my motor?

    Thanks
     

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    Last edited: Apr 22, 2016
  2. you should have the carb mounting pad on the intake leveled side to side and front to back with the car at ride height. If it has any rake to it and you set it up with the frame level and the carb level, the motor will now be tilted down slightly. Could cause the oil to not run back to the sump in the oil pan and can cause carb float problems depending on how severe the angle is. Set the frame at ride height then level the carb.
     
  3. F&J
    Joined: Apr 5, 2007
    Posts: 13,217

    F&J
    Member

    Yes , what he said: you need the frame "rake" at where you want it for looks, then get the carb level.

    Then the pinion shaft angle needs to be same as crankshaft angle...or close as possible.
     
    clem likes this.
  4. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,796

    tfeverfred
    Member

    My target is 3 degrees. Won't know for sure, until things get shifted into position.
     
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  5. Flathead Dave
    Joined: Mar 21, 2014
    Posts: 2,852

    Flathead Dave
    ALLIANCE MEMBER
    from So. Cal.

    I added two new pics at the intake at ride height. I used shims to level from front to rear in one pic. In the second added blurry pic is the non level with out the shims. I am level side to side. I will need to shim the motor mounts to level the motor front to rear. I did not have to level rear to front. Am I good to go?
     

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  6. bonzo-1
    Joined: Oct 13, 2010
    Posts: 328

    bonzo-1
    Member

    set the motor down 3 degrees to the back and the diff pinion 3 degrees up. Dont measure on the carb, measure on a pan rail or anything else that is parallel with the crank
     
  7. F&J
    Joined: Apr 5, 2007
    Posts: 13,217

    F&J
    Member

    QUOTE:"set the motor down 3 degrees to the back and the diff pinion 3 degrees up."

    Where are you guys coming up with a random 3 degrees?

    Some real early cars were nearly zero...meaning those engines had the oil sump and carb flange set to near zero..

    And why would you measure the pan rail, rather than where the carb sits? The carb want's to be level, not the panrail.

    not making any sense here

    Example: if you choose 3 degrees up on pinion, and 3 down on engine, AND if the two are very close to each other, and heights differ a lot , then the U-joint working angle will be wrong(too severe of angle). If they are very far apart, the working angle decreases.


    "3 degrees" is the norm for the "optimum working angle of a needle type cross U-joint".(that keeps the grease flowing under the needles) That 3 has nothing to do with motor angle set to 3. The working angle comes "also" from height difference of pinion and crank, and distances


    Back to the real old cars again: Both the crank and the pinion would be near zero on some old cars, but because the height difference between crank and pinion, you can still get 3 degrees at the U-joints
     
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  8. tfeverfred
    Joined: Nov 11, 2006
    Posts: 15,796

    tfeverfred
    Member

    I get 3 degrees from my last car. My new one may differ. It's an ESTIMATE, in MY case.
     
  9. F&J
    Joined: Apr 5, 2007
    Posts: 13,217

    F&J
    Member

    To the OP;

    set the car chassis to the exact rake (or level , if that is what you want).

    next, move the motor until the carb is level, front to rear.

    next, set the pinion shaft angle the same as the engine crankshaft/trans output shaft angle. (in other words, if the back of engine is tilted down X degrees, the back of the pinion is also "down" the same degrees) Better way to see the angles is, if the "front" of the motor is "up" X degrees, then the "front" of the pinion is "up" the same degrees

    now run a string line or whatever, to be where the imaginary drive shaft center line will be. Now is when you measure the working angle of the U-joints. You are measuring the difference between driveshaft and engine crankshaft centerline. (and pinion). 3 is considered "optimum" as far as enough movement to lube the needles, but not enough severe angle to cause vibration. There are specs on the net for "U-joint angles". Those specs will say how severe of an angle is OK, and how much is not enough of an angle. I believe the "maximum" specs change a bit depending on driveshaft length. (this relates to vibration elimination in their charts)

    They will/should also have a spec on "mismatch" of angles of the two joints, but it's minimal
     
  10. clem
    Joined: Dec 20, 2006
    Posts: 2,810

    clem
    Member

    Now ,
    When you have that all sorted,

    Remember.....

    Only drive on flat roads,
    Don't drive around corners as the centrifugal forces will hinder carb function.
    Only park your car on the flat when not in use.
    Don't even dream of driving up or down hills
    Now you are good to go. :)
     
  11. Flathead Dave
    Joined: Mar 21, 2014
    Posts: 2,852

    Flathead Dave
    ALLIANCE MEMBER
    from So. Cal.

    1951 8BA Flathead w/C-4 transmission.
    Frame is at ride height.
    I get the pinion set up.
    I went back to my motor and looked at things again. If I do not shim the motor mounts, I will need to drop the rear of the motor down. But the transmission pan is sitting 5" from the floor now.
    The top of my motor mounts are flush with the top of the frame.
    If I measure at the oil pan rails, I am at 3 degrees but the intake/carb is also at 3 degrees and not at zero.
    All measurements are done on the same side of the motor.
    When I measure at the intake/carb, I get 3 degrees and can shim the motor mounts to zero it out with out dropping the rear of the motor, which would be the same thing as dropping the rear of the motor but easier and probably safer due to the clearance of the transmission. (sounds like My name Is Earl)
    Can shimming the motor mounts be done to gain zero degrees at the intake/carb?
     
    Last edited: Apr 22, 2016
  12. mountainman2
    Joined: Sep 16, 2013
    Posts: 316

    mountainman2
    Member

    Where I live (Missouri Ozarks), I'm pretty sure my car is never level on either axis for more that 10 seconds out of each minute and never continuously.
     
    shawnsauto1 likes this.
  13. The key variable here is if your frame is at the actual ride height for when the car is on 4 wheels with the rake of how you want the frame to sit. Almost no real hot rod frames are perfectly level when finished. The frame needs to be at least close to the finished ride height or you measurements mean nothing.
     
  14. patmanta
    Joined: May 10, 2011
    Posts: 3,525

    patmanta
    ALLIANCE MEMBER
    from Woburn, MA
    1. MASSACHUSETTS HAMB

    If it helps, I have found that 1/8" nets you about 1° on an 8ba with the 39 trans I'm running. I put a washer from another biscuit mount setup under my mounts to shim them up when the raised mounts I put on weren't quite enough. I have not run this though.

    [​IMG]
     
  15. bonzo-1
    Joined: Oct 13, 2010
    Posts: 328

    bonzo-1
    Member

    ---------------------------------------
    Yes, 3 degrees is optimal u joint working angle. From the pics the shaft is not short.

    Correct, the u joint working angle is determined from the drive shaft not the frame. Keep the the trans output and pinion at the same but opposite angle at ride height. If you add the two angles together you want 0 (-2.5 + 2.5 = 0)

    No carb measurement mentioned here because it doesn't matter. (within reason) Use something that is in line with the crank. The carb is not one of those things. Intakes and carbs are not all the same.
     
  16. If you want to be right on the gnat's ass you set the chassis at ride height/angle and then set your motor.

    Something to think about is that we took factory cars of all makes and models and raked 'em, dumped the front or the rear changed the tires and etc. We never changed the engine angle at all just modified 'em and drove 'em, no problems.
     
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  17. alchemy
    Joined: Sep 27, 2002
    Posts: 15,371

    alchemy
    ALLIANCE MEMBER

    Carbs aren't that touchy. Set the engine in the frame so it fits and the driveshaft is right, not the carb. And if you are a real worry wart about the float, change to a Stromberg 97 as they are hinged from the side.
     
    clem likes this.
  18. You might want to check the angle of the block without the intake , as later intakes have carbs angled to make up for greater angle of the engine , early blocks set almost parallel with frame rails . Set your ride height , pinion angle , tail shaft angle , then deal with your carb .
     
  19. 1946caddy
    Joined: Dec 18, 2013
    Posts: 1,653

    1946caddy
    Member
    from washington

    The 3 degrees has nothing to do with up or down of the engine but is the angle of the drive shaft as it relates to the rear differential u joint and the transmission u joint. You can use 2 degrees or 4 degrees and it doesn't make a whole lot of difference but they need to be the same. Set your frame at ride height and then set your rear end up 3 degrees and then set your engine to down 3 degrees. This angle will stay the same wither your going up a hill or have a fat chick in the back seat. The purpose of the 3 degrees is to assure proper lubrication of the u joints and to keep them in faze.
     
  20. Spicer and Dana have good info, on achieving proper driveline inclination.
    It all begins, however, with a level carb base, measured at the intake.
     
  21. dirt t
    Joined: Mar 20, 2007
    Posts: 4,594

    dirt t
    ALLIANCE MEMBER
    from Kingman,AZ
    1. HAMB Old Farts' Club

    I have found that when I have the engine level the output shaft of the trans is 3* down.
     
  22. That number sounds close to correct, with a level base on the intake.
     
  23. clem
    Joined: Dec 20, 2006
    Posts: 2,810

    clem
    Member

    Wouldn't drive shaft length and/or plane of u joints all have a bearing on this ?
     
  24. 1946caddy
    Joined: Dec 18, 2013
    Posts: 1,653

    1946caddy
    Member
    from washington

  25. Kail
    Joined: Jul 7, 2007
    Posts: 825

    Kail
    Member
    from Austin, TX

    I think the industry standard of 3 comes from the the fact that motors like the SBC have a crank angle of 3 when the carb is at 0. With that said I normally zero out the carb at loaded ride height, measure the trans output angle and set the rearend at the opposite ie 3-/3+
    And I would invest in an actual degree finder, the analog one is maybe 10-15$ digital is my preference
     
    clem likes this.

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