1.5 vs. 1.6 Roller Rockers

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

  1. Rustbucket350

    Rustbucket350 Veteran Member

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    Sep 4, 2013
    Oviedo, Florida
    All of this is accurate. The 1.6 will add more lift and some duration to the valves. They also add more force between the lobe and lifter which is multiplied by the spring rate. I never had a problem with longer rockers on stock cams besides pushrod hole size, but on max effort motors... It's a good way to crush the lobes to dust. I do agree with them being a bandaid for wrong cam choice and I really don't like the extra effort in measuring pushrods involved in them. I wouldn't recommend a longer rocker unless the motor was already well broken in and you wanted to see what a little extra valve opening would do.
     
  2. slayer021175666

    slayer021175666 Veteran Member

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    Feb 29, 2016
    Idaho
    Ya. Get the correct cam in the first place. If you want to try the 1.6s later, go for it. I wouldn't, though. Waste of $$, waste of time and screws up your valve train geometry. If you buy your cam from the pros (Lunati, Competition. etc.) and actually give them all of your specs, they aren't going to leave any grunt on the table that you could extract by using 1.6 rockers. They will build you a cam that will get all the grunt you are ever gonna get out of your combo!
     
  3. tom3

    tom3 Veteran Member

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    ohio
    With your lower lift stock grind and decent heads I suspect you'll see a difference in performance. I'm running a Performer Plus cam with flat tappets. Looking to get more lift with this somewhat aggressive profile I put on a set of Pro Magnum 1.6 rockers, did feel some difference with this. No problems for a couple years now. Really a good mid rpm range cam there. Simple math, lift divided by 1.5 times 1.6 to get result.

    Edit: I just noted you said stock duration on that cam, lift? If that cam (roller cam) has some serious lift with the lower duration you may not actually see any real improvement.
     
  4. G72Zed

    G72Zed Veteran Member

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    Canada
    Good point, but most of the stuff that goes into an EMC entry is at the "edge" and you do crazy things to bring up the TQ/HP averages, but I have seen when the engine is sold to a customer, things get changed out, like cam/lifters/PR and rockers.

    I have also seen 1.5 RR with bad geometry, and the replacement 1.6 rocker from a different manufacturer was better in every way!!
     
  5. Lowend

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

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    Mar 25, 1999
    San Jose, CA, USA
    I'm opinions on high ratio rocker arms are pretty well known.
    Here are the cliff notes:
    Camshaft lobe design is a complicated undertaking. Mechanical engineers spend many-many hours working out portions of the design that no-one ever considers; things like lifter contact angle, lifter loft, valve closing speed. These specs are designed with a specific rocker ratio in mind. In most cases, the factory rocker ratio for a given engine (1.52 on a small block).
    You (and I) are not more knowledgeable than the engineers who are designing cam lobes. You will not out-smart them with a set of 1.6 ratio rocker arms.
    Unless a cam is designed specifically with a higher rocker ratio in mind, leave it alone.
     
    Last edited: Jan 27, 2018
  6. Chevyforever

    Chevyforever Veteran Member

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    Jan 4, 2011
    ontario
    1.52 is not the OE ratio,but rather something the aftermarket ( notably Comp cams )got going back in the early 80's.
     
  7. Lowend

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

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    San Jose, CA, USA
    That's untrue. The factory ratio was always 1.52 and was rounded down to 1.5
     
  8. Chevyforever

    Chevyforever Veteran Member

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    Jan 4, 2011
    ontario
    1.52 Huh, ? Can you please refer me to where this is published ? I respectfully disagree at this point.
     
    Last edited: Jan 30, 2018
  9. larrylarry

    larrylarry Veteran Member

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    San Antonio Tx
    NASCAR use to adjust weaker cylinders/ ones that didn’t flow as well as others with different ratio rockers.
     
  10. SS Performance

    SS Performance Veteran Member

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    Nov 17, 2016
    I've been around cars and Chevy's in particular since the 70's. To the best of my memory the stock ratio for small blocks has always been 1.52. I'm sure if you look in some older HP books you will find it there. Most after market companies round the ratio to 1.5.
     

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