Difference between stock '75 rocker arms and the L and R ones.

Discussion in 'Race 400/430/455' started by Bogus919, Dec 22, 2020.

  1. Bogus919

    Bogus919 Silver Level contributor

    I've read a few threads on here about the different types of stock rocker arms that are available ... seems you can get a "centered" one as well as specifically for the L and R side of the piston (not the L and R side of the engine). Anyway... I was going through my valvetrain and cleaning it up when I noticed some galling on a couple of my rockers and so I decided to replace them.... since one was on the left side of it's piston and the other was on the right side of another piston, I decided to pick up some L and R stamped rocker arms.

    Since there are a few threads about this but no pictures, I figured I'd post the differences for those of us to see who haven't seen them.

    From the top they don't look that much different, other than the obvious stamping of L and R. The one in the middle is my factory rocker that appears to be more centered than the others. From the bottom though, you can definitely tell that the pushrod seat is off to one side as well the oiling hole seems to be in a different place.

    I'll have to wait to see if they perform any different but I will be sure to have the valve cover off when I am priming to make sure they are oiling properly.
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  2. DasRottweiler

    DasRottweiler -BuickAddict-

    I think that the reason for the offset with the "service " rockers is to better center the pushrod in the head for improved geometry. Jim
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  3. tommieboy

    tommieboy Well-Known Member

    Not quite sure how to visualize that? But looking at the cylinder head (from the exhaust side of the head) the "L" stamped rocker arms should be located on the left side of the rocker shaft towers, and the "R" stamped rocker arms located on the right side of the rocker shaft towers.

  4. DasRottweiler

    DasRottweiler -BuickAddict-

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    Attached Files:

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  5. No Lift

    No Lift Platinum Level Contributor

    IIRC most early factory stamped rockers were of the L/R variety. Only the later engines started coming up with the universal centered rockers. Apparently Buick/aftermarket may have reconsidered this move if they went back to the L/R for replacement use.
  6. DasRottweiler

    DasRottweiler -BuickAddict-

    I'm think you are mistaken, the stamped rockers I have are all aftermarket, while the unstamped/ centered rockers I have are from an unmolested, never rebuilt 71 455. Jim
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  7. Bigpig455

    Bigpig455 Fastest of the slow....

    I've heard the centered rockers are stronger than the L/R, which are stronger than the aluminum. Per the bulletin, you need to make sure youve got your pushrod holes in the head enlarged to .5625 if you are using the centered steel rockers
  8. Mark Demko

    Mark Demko Well-Known Member

    The "L" and "R" refer to the offset of the pushrod seat in the rocker arm.
    I have dozens of replacement rocker arms, most early replacements were correctly offset and marked accordingly.
    Later replacements are a hodge podge of rockers, some were marked "L" and "R" but the pushrod seat was centered, some were offset but no designation.
    What I think is going on is the manufacturer doesnt care, or its sloppy work, maybe a combination of both.
    The important thing is to keep the pushrod somewhat centered in the hole in the head.
  9. Bogus919

    Bogus919 Silver Level contributor

    Hey, same topic but different issue....I had a heck of a time getting the factory original nylon buttons off.... but the replacements, though not super easy to install... seem to be much easier to remove. The three rows of “teeth” almost all shaved off when installing in the shaft hole. Did anybody else have this issue? I would think I shouldn’t be able to remove the new ones with just a good tug, they should require substantial force like the factory set did (I chiseled them off). I got these from Rock Auto, maybe they are for a different vehicle. Anyway, thinking of going with another set to see if they are any better.
  10. DasRottweiler

    DasRottweiler -BuickAddict-

    I bought mine from. TA Performance.
    I've always felt that it would be better to tap n thread the shafts, then machine a metal thread-in button, but hey it's been working for 50+ years....JIM
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  11. No Lift

    No Lift Platinum Level Contributor

    I think the original have been subjected to heat and oil for so long that they harden and that is why you have to chisel them out. The new ones are much softer but it is not unususl to gack a couple up putting them in. You really need to set them up to knock them in with one or two smooth straight blows. On the other hand that is why I always have more than one set around when installing new buttons.
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  12. Jim Weise

    Jim Weise 1000+HP

    When installing the nylon buttons, the best way to do it is to bolt the shaft to a head.. then use a punch that is nearly the same size as the head of the nylon button. Put a touch of grease on the shaft of the button, line it up square, and knock it in with a couple sharp blows.

    I used to break a couple now and then when I was trying to do it on the workbench.. have not broken one on install since I started bolting the shaft to a spare head. And I have done hundreds of them..

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  13. DasRottweiler

    DasRottweiler -BuickAddict-

    I messed up one of my buttons on install. From now on , I'll do as JW suggests and bolt the shaft to a spare head to knock em in, to prevent the shaft from spinning whilst hammering. Luckily TA had 17 in the package! JIM
  14. Schurkey

    Schurkey Silver Level contributor

    I went out of my way to get a giant, heaping pile of L-R rockers before the supply dried-up. I figured they were better for pushrod geometry. Thought I was doing the smart thing.

    Then I read on this forum that the hot tip is the aluminum rockers. I've always distrusted aluminum rockers in general--not merely OEM rockers, but aluminum "roller rockers" too.

    I'm way less concerned about rocker ratio--I've heard there's a small difference between aluminum and stamped-steel--than I am about strength with stiffer-than-stock valve springs. Is there a consensus on the "best" OEM, or OEM-style (stock replacement) rockers?
  15. tommieboy

    tommieboy Well-Known Member

    70 - 72 rockers where cast aluminum. 73 on up were stamped steel.

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  16. tommieboy

    tommieboy Well-Known Member

    That's odd in that all the production line 455 stamped steel rockers that I came across were centered to begin with.

  17. Mark Demko

    Mark Demko Well-Known Member

    My '71 GS 350 had stamped steel rockers, 88,000 mi all original when I bought it.

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