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1.6 roller rockers-- worth it? How hard to install??

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by ErikH, May 19, 2001.

  1. ErikH

    ErikH 1/2 ton status

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    I'd like to squeeze a little more juice out of an otherwise mildly modified 350 (Edelbrock intake and carb, wide open exhaust), and I'm looking at upgrading to 1.6 ratio roller rockers. The valvetrain is currently stock, including cam.

    My question: Are these 1.6 roller rockers just a bolt-on job, or is there more to it? And will I really see an HP gain, like the ads claim? Thanks.

    Erik
     
  2. Roostr84

    Roostr84 1/2 ton status

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    Well it is a bolt on affair, you just have to reset the valve lash, and then pop back on the covers. Something I would look at is the current specs of your cam. That way you will be able to determine the change in lift and duration with the larger rockers. From what I have read and heard going from a stock stamped steel rocker to a full roller along with the 1.6:1 ratio will be good for about 10+/- horsepower. The benefit really comes from the reduced friction as well as the general loosness in quality control with the stock rockers. Often times the ratios are much less than the 1.52:1 they are supposed to be.
    HTH's
    Chris

    Chris =)
    http:// www.roostr84.coloradok5.com <P ID="edit"><FONT SIZE=-1>Edited by Roostr84 on 05/19/01 09:19 PM (server time).</FONT></P>
     
  3. Steve_Chin

    Steve_Chin 1/2 ton status

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    Given a stock valve train, 1.6:1 rockers are not always a bolt-on affair. You MUST check your coil bind height and your retainer to valve guide clearance to ensure that you will not end up banging the coils together and to ensure that you won't end up smacking the retainers into the valve guides. Further, you *must* have at least 0.050" of space between each coil at full valve lift. Most factory spring sets are not capable of handling the increased lift at any sort of meaningful RPM.

    Often, you must machine the pushrod holes in the heads because the ball socket in a 1.6:1 ratio rocker arm is closer to the rocker stud than that of a 1.5:1 rocker. The next issue has to do with longevity: Most Chevy small-block heads have whimpy 3/8" pressed-in studs. The higher ratio rocker arms impart higher levels of stress into the studs and might cause stud failure or pull-out. It is a wise idea to modify the heads for screw-in studs of the 7/16" variety.

    Once you get all of that sorted out, you need to ensure that your valve train geometry is correct. The tip of the rocker arm must reside in the middle of the tip of the valve stem at half of gross valve lift. If it does not, you will not be providing the valvetrain with full lift and might possibly be imparting strange wear characteristics into the valvetrain. Geometry is altered by choosing different length pushrods.

    Finally, whether or not you see any increase in power is partially due to the ports in your heads. If they can barely support the lift of the stock valve train, you will only see a token increase in power (you may not feel it in the seat of your pants) due to the increase in effective off the seat time of the valve and increased valve acceleration.

    Don't forget that you might have to rejet your carburetor to take advantage of the new valve lift and timing...
     
  4. Roostr84

    Roostr84 1/2 ton status

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    Thats definetly true Steve about the coil bind etc. I guess it just depends on the year of the "stock" motor and cylinder head. Plus I think most street guys would stick with a stock pushrod length and with a relatively mild cam and/or sane RPM's the stock stud would work. You definetly brought up some considerations though and wise advice. Can never hurt to upgrade.

    Chris =)
    http:// www.roostr84.coloradok5.com
     

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