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Thread: Mixed Rocker Arms

  1. #1
    Join Date
    Apr 2002
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    St. Louis
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    Question Mixed Rocker Arms

    Here's a good question for ya'll. I heard that some people when setting up there motor actually mix there rocker arms (i.e. 1.5 ratio and 1.6 ratio). What is the benefit in doing this, and which valve (exhaust or intake) would you put the 1.6 on?
    Last edited by unzer; 10-07-2002 at 02:26 PM.

  2. #2
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    Apr 2002
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    Toronto, Canada
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    Firstly, the stock rockers are 1.73 ratio, so no one would be using 1.5 or 1.6 on these motors, unless they had a cam re-grind to compensate.

    I once pondered the idea of putting 1.73 on all the intake valves, and adding 1.8 rockers to all the exhaust. Keeping in mind I already have roller rockers, which do not come stock.

    It would take an engine builder or someone with equivilant knowledge to answer if this is possible.

  3. #3
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    Aug 2002
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    Corpus Christi,TX
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    This comes from the Chevy camp, more specifically from the roundy-round crowd, IIRC.

    The SBC tends to be more intake limited than most Fords and it was found some years back that putting 1.6 rockers on the intake helped power output. Higher ratios didn't work so well on the exhaust since flow there was good enough in the first place and running the 1.5's reduced wear.

    A further variation found that not all cylinders needed to have the longer ratios. Again IIRC, its the outer 4 cylinders on the SBC that could use some help due to the longer flow path. I've got the info in my pile o' stuff somwhere.

    Typically a Ford wants more exhaust flow in relation to the intake. So an engine with a single-pattern cam could possibly improve matters by using a longer ratio rocker on the exhaust side.

  4. #4
    Join Date
    Oct 2002
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    Up in the SKY!!
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    1,197

    well

    I have ran 1.65s on the intake and 1.7s on the exhaust. You could run whatever you wanted if you had a rocker arm studs and the proper fulcrum lengths for proper roller tip to valve end alignment. I initially did it to achieve a higher lift on the exhaust side to help bring my flow percentages closer to 95%. Even now with a dual pattern cam I am running different rocker arms on the intake and exhaust. It all depends on what you are trying to achieve with your particular setup.

    Chris
    Chris' Current Stable:
    1990 35th SC - Still under the knife.
    441.89 RWHP/403.88 RWTQ
    11.820 @ 114.71
    2014 Hyundai Veloster TURBO baby!!! HAHA!

  5. #5
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    Sep 2002
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    this sounds vary intresting to know because I'm looking to build a motor in the next year. so if you have some more info about this can you post it or e-mail me at sc_thunder95@hotmail.com

    thanks a lot jason

  6. #6
    Join Date
    Apr 2002
    Location
    St. Louis
    Posts
    30

    Talking Mixed Rocker Arms

    Yes, that did come from the Chevy camp. I've been a bow-tie man ever since I can remember. This here is my first SC (actually the second I've driven, that's why I bought one).

    You said it depends on what I'm looking to get out of my set-up, what difference would I get between using the higher ratio on the exhaust as opposed to using it on the intake? Also is it different for a rock (chevy).

    I'm building an El Camino w/ a 67, 327 and this info is all useful. Thanks.
    Last edited by unzer; 03-11-2004 at 03:04 PM.

  7. #7
    Join Date
    Apr 2002
    Location
    Edgewater, CO
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    133
    I did the 1.73 and 1.80 succesfully on the CMRE 2 heads, with the use of lash cap and had to mod the geometry some. Ran great ! Now I'm using 1.80 on both sides and lifting .610. Idle is a little lumpier but it's got gobs of torque in Part Throttle !!!

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