1.5 vs. 1.6 Roller Rockers

Discussion in 'Engine Topic' started by iraqivet, Jan 24, 2018.

  1. Chevyforever

    Chevyforever Veteran Member

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    As a quick reference, the Chevrolet Power Service Manual from 1988 states "Production Chevrolet small-block rocker arms have a nominal ratio of 1.5 :1." Another source book by David Lewis states " ROCKER ARM GEOMETRY Small-block Chevrolet rocker arms (part number 3974290) are of the ball-and-socket type. A 1.5:1 ratio isbuiltinto the rocker, and the rocker's stud ... In 1990, GM introduced a self-aligning rocker with built-in alignment rails at the rocker tip." I too have been around Chevy V-8 engines for more than 40 years. Built a few small blocks and many big blocks, worked as a speed shop manager from 1980 to 1985. Worked the parts counter at numerous jobber parts stores and managed an ACDelco store for 7yrs. I also have drag raced on and off since I was 16 yrs of age. NHRA tech in stock eliminator uses 1.5 ratio as the spec when checking lift at Natl events etc ...

    The common example many cite is .300 lobe lift X 1.5 rocker ratio = .450 lift.
     
  2. Chevyforever

    Chevyforever Veteran Member

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    Rocker Arm Ratio - Super Chevy Magazine
    www.superchevy.com › Super Chevy › How To › Engines & Drivetrain
    Feb 1, 2002 - The debate over the optimum rocker arm ratio has dragged on since the invention of the pushrod V-8. Even though Chevrolet made the decision easy for us when it engineered the small-blockto run around a 1.5:1 ratio, (Comp Cams says most stock rockers are actually about 1.46:1), it's well known that the ..
     
  3. G72Zed

    G72Zed Veteran Member

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    Sep 8, 2015
    Canada
    Totally agree with the cliff notes Lowend. Cam design gets so involved and deep and can lead you down the "rabbit hole" of cam choices and might leave your head spinning and you can't decide what to get!! Work with the pro's, and stick to the OEM parameters to start.

    BUT, what I have experienced first hand, is when you are looking for "trends" in what a combo wants with the parts you have, or responds too, adv/ret phasing, lash loops & settings, including Rocker ratios changes (+ or-) on int and/or ex, (or only the outside cylinders) with correct geometry, it helps you determine what way to go for a new/diff. or custom spec'd cam.

    In my opinion, the only way to find out is testing it, my close R&D partner has participated in 7 EMC's since '09, the stuff that goes into testing for this competition is bordering on the absurd.

    I looked at the video, the gain of .037 lift on both Int & Ex. with the 1.6 ratio Rockers gave a + 20 HP peak, and shows the trend in that particular combination. They should do a video of them trying the 1.65 - 1.7's with a stud girdle and .120 wall push rods just to see what happens.
     
  4. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

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    I don't see anywhere that says 1.50-1
     
  5. Chevyforever

    Chevyforever Veteran Member

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    Jan 4, 2011
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