1.6 rocker arm swap on L65 with 882 heads

Discussion in 'Tips 'n' Tricks Topic' started by gmacheen, May 7, 2020.

  1. gmacheen

    gmacheen New Member

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    Good morning all! I have a 1975 L65 350 with a stock bottom end. Mods to date:
    -mid length headers & 2.25" dual exhaust
    -aluminum dual plane intake
    -4bbl Q-jet
    -bumped up timing
    -HEI distributor re-curve

    Until I can afford a cam & head swap, I'm considering swaping out the factory stamped 1.5 rockers for 1.6 rollers for a little extra valve lift, has anyone done this? My concerns are (given the following factory specs: stock cam with 0.300/0.307 int/exh lobe lift & stock 882 heads with 1.5 ratio stamped rocker arms, therefore 0.45/0.46 ink/exh):
    a) will the stock 882 heads handle the extra lift with 1.6 rockers (0.48/0.49 int/exh)?
    b) will piston to valve clearance be an issue with the extra lift

    This is a weekend street machine & I'm just looking for a little extra giddy-up! Any advise/experience would be much appreciated. Maybe I should do a little home porting/port maching???
     
  2. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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  3. Lowend

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

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    The 1.6 rocker arms will not provide any significant increases here.
    Save your money for the cam swap
     
  4. gmacheen

    gmacheen New Member

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    Thanks Lowend! Is it worth swapping the cam (comp XE268 for example) without changing the heads? I'm only looking for low-mid range torque. Can anything be done to the 882's to make them usable with a mild cam?
     
  5. G72Zed

    G72Zed Veteran Member

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    I have tried this many times on the dyno/track. Typical pump gas street SBC, 350 to 600HP, and if the cam is close for the combo, the 1.6's give very little in the cases I have been part of, 2-6 HP peaks, and less in the ave vs 1.5. Sometimes a loss occurs due to acceleration rates and spring surge because there not happy.

    The SBC race engines are in the 1.75-1.8+ ratio's, but that's shafts. On the dyno testing my own SBC last Friday, had a new set of ARC 1.6's, did not even try them out. I would have tried 1.35 on the exhaust's before 1.6's on the intakes.

    A little "home porting, port matching" (not gasket matching) will go a lot further, and it's fun to do.
     
  6. jeff swisher

    jeff swisher Veteran Member

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    Yes Yes Yes!
    40 hp waiting to be ground out of those heads and take them down to the local machine shop and have .030" taken off of them.
    Stick a .015" 1094 head gasket onto it and you are golden.
    That is if the pistons are down the hole a ways like most production blocks are.

    You must elongate the pushrod slot in the heads for running 1.6 rockers as it moves the pushrod cup on the rocker closer to the stud.
    I like my 1.5 rockers just fine.
    I never felt anything from a rocker change.
    Run 110 seat pressure with that 268 cam also.. keep open pressures below 300 psi.
    I run crower hydraulic cam saver lifters on my flat tappets and use Gibbs/Driven break in oil.
    No fails with that combo.. then VR1 or Gibbs/ Driven hot rod oil.

    That XE268H and ported heads will most likely like to be shifted at 6500 rpm ..Good combo.
     
  7. G72Zed

    G72Zed Veteran Member

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    And there is a KEY phrase, what does one "feel" or experience with a rocker ratio change. The head CFM would tell you the CFM gain, the dyno will tell you if the combo likes or needs it the extra ratio, the track may or may not support the bench or dyno.

    Try this, take an assembled bottom end, no rods or pistons, cam & chain connected, put a torque wrench on the crank snout and setup 1 valve with actual springs. Go from 1.3 to 1.7 ratio and see what the TQ difference is to turn over, I'm only referring to stud mounts.
     
    jeff swisher likes this.
  8. Lowend

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

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    Personally - unless you are working with a specific class or trying to keep originality, I really wouldn't put a dime into any pre-87 factory head. They just aren't that good.

    The Vortec L31 heads are better than most ported factory heads, out of the box. They also have some very cool tech to prevent preignition etc. Go figure, after 45 years of R&D Chevy came up with a better design.
     
  9. djorgensen3

    djorgensen3 Veteran Member

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